drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validationgrafted

amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and
uses the first encoding that validates. YCbCr 4:4:4 is listed before
RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the
"color format" property is left at AUTO, even though RGB fits the same
link.

That contradicts the documented AUTO behaviour for HDMI in enum
drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when
the bandwidth is not available or the mode is 4:2:0-only), which the
amdgpu implementation of the property also describes. It also leaves
the "Broadcast RGB" property without effect on such sinks, since the
quantization range it selects only applies to RGB output.

Try RGB first. The mask still holds every encoding the sink supports,
so a mode that cannot carry RGB falls back exactly as before.

For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced
through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI
sink that advertised it.

Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation")
Suggested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Assisted-by: Claude Code:claude-fable-5-1
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7)

7 files changed, 2010 insertions, 0 deletions

diff --git a/drivers/soc/aspeed/Kconfig b/drivers/soc/aspeed/Kconfig
new file mode 100644
index 000000000..63a656449
--- /dev/null
+++ b/drivers/soc/aspeed/Kconfig
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+if ARCH_ASPEED || COMPILE_TEST
+
+menu "ASPEED SoC drivers"
+
+config ASPEED_LPC_CTRL
+	tristate "ASPEED LPC firmware cycle control"
+	select REGMAP
+	select MFD_SYSCON
+	default ARCH_ASPEED
+	help
+	  Control LPC firmware cycle mappings through ioctl()s. The driver
+	  also provides a read/write interface to a BMC ram region where the
+	  host LPC read/write region can be buffered.
+
+config ASPEED_LPC_SNOOP
+	tristate "ASPEED LPC snoop support"
+	select REGMAP
+	select MFD_SYSCON
+	default ARCH_ASPEED
+	help
+	  Provides a driver to control the LPC snoop interface which
+	  allows the BMC to listen on and save the data written by
+	  the host to an arbitrary LPC I/O port.
+
+config ASPEED_UART_ROUTING
+	tristate "ASPEED uart routing control"
+	select REGMAP
+	select MFD_SYSCON
+	default ARCH_ASPEED
+	help
+	  Provides a driver to control the UART routing paths, allowing
+	  users to perform runtime configuration of the RX muxes among
+	  the UART controllers and I/O pins.
+
+config ASPEED_P2A_CTRL
+	tristate "ASPEED P2A (VGA MMIO to BMC) bridge control"
+	select REGMAP
+	select MFD_SYSCON
+	default ARCH_ASPEED
+	help
+	  Control ASPEED P2A VGA MMIO to BMC mappings through ioctl()s.  The
+	  driver also provides an interface for userspace mappings to a
+	  pre-defined region.
+
+config ASPEED_SOCINFO
+	bool "ASPEED SoC Information driver"
+	select SOC_BUS
+	default ARCH_ASPEED
+	help
+	  Say yes to support decoding of ASPEED BMC information.
+
+endmenu
+
+endif
diff --git a/drivers/soc/aspeed/Makefile b/drivers/soc/aspeed/Makefile
new file mode 100644
index 000000000..b5188dcde
--- /dev/null
+++ b/drivers/soc/aspeed/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_ASPEED_LPC_CTRL)		+= aspeed-lpc-ctrl.o
+obj-$(CONFIG_ASPEED_LPC_SNOOP)		+= aspeed-lpc-snoop.o
+obj-$(CONFIG_ASPEED_UART_ROUTING)	+= aspeed-uart-routing.o
+obj-$(CONFIG_ASPEED_P2A_CTRL)		+= aspeed-p2a-ctrl.o
+obj-$(CONFIG_ASPEED_SOCINFO)		+= aspeed-socinfo.o
+CONTEXT_ANALYSIS_aspeed-lpc-snoop.o	:= y
diff --git a/drivers/soc/aspeed/aspeed-lpc-ctrl.c b/drivers/soc/aspeed/aspeed-lpc-ctrl.c
new file mode 100644
index 000000000..4d8574cac
--- /dev/null
+++ b/drivers/soc/aspeed/aspeed-lpc-ctrl.c
@@ -0,0 +1,356 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2017 IBM Corporation
+ */
+
+#include <linux/clk.h>
+#include <linux/log2.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/regmap.h>
+
+#include <linux/aspeed-lpc-ctrl.h>
+
+#define DEVICE_NAME	"aspeed-lpc-ctrl"
+
+#define HICR5 0x80
+#define HICR5_ENL2H	BIT(8)
+#define HICR5_ENFWH	BIT(10)
+
+#define HICR6 0x84
+#define SW_FWH2AHB	BIT(17)
+
+#define HICR7 0x88
+#define HICR8 0x8c
+
+struct aspeed_lpc_ctrl {
+	struct miscdevice	miscdev;
+	struct regmap		*regmap;
+	struct clk		*clk;
+	phys_addr_t		mem_base;
+	resource_size_t		mem_size;
+	u32			pnor_size;
+	u32			pnor_base;
+	bool			fwh2ahb;
+	struct regmap		*scu;
+};
+
+static struct aspeed_lpc_ctrl *file_aspeed_lpc_ctrl(struct file *file)
+{
+	return container_of(file->private_data, struct aspeed_lpc_ctrl,
+			miscdev);
+}
+
+static int aspeed_lpc_ctrl_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct aspeed_lpc_ctrl *lpc_ctrl = file_aspeed_lpc_ctrl(file);
+	unsigned long vsize = vma->vm_end - vma->vm_start;
+	pgprot_t prot = vma->vm_page_prot;
+
+	if (vma->vm_pgoff + vma_pages(vma) > lpc_ctrl->mem_size >> PAGE_SHIFT)
+		return -EINVAL;
+
+	/* ast2400/2500 AHB accesses are not cache coherent */
+	prot = pgprot_noncached(prot);
+
+	if (remap_pfn_range(vma, vma->vm_start,
+		(lpc_ctrl->mem_base >> PAGE_SHIFT) + vma->vm_pgoff,
+		vsize, prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static long aspeed_lpc_ctrl_ioctl(struct file *file, unsigned int cmd,
+		unsigned long param)
+{
+	struct aspeed_lpc_ctrl *lpc_ctrl = file_aspeed_lpc_ctrl(file);
+	struct device *dev = file->private_data;
+	void __user *p = (void __user *)param;
+	struct aspeed_lpc_ctrl_mapping map;
+	u32 addr;
+	u32 size;
+	long rc;
+
+	if (copy_from_user(&map, p, sizeof(map)))
+		return -EFAULT;
+
+	if (map.flags != 0)
+		return -EINVAL;
+
+	switch (cmd) {
+	case ASPEED_LPC_CTRL_IOCTL_GET_SIZE:
+		/* The flash windows don't report their size */
+		if (map.window_type != ASPEED_LPC_CTRL_WINDOW_MEMORY)
+			return -EINVAL;
+
+		/* Support more than one window id in the future */
+		if (map.window_id != 0)
+			return -EINVAL;
+
+		/* If memory-region is not described in device tree */
+		if (!lpc_ctrl->mem_size) {
+			dev_dbg(dev, "Didn't find reserved memory\n");
+			return -ENXIO;
+		}
+
+		map.size = lpc_ctrl->mem_size;
+
+		return copy_to_user(p, &map, sizeof(map)) ? -EFAULT : 0;
+	case ASPEED_LPC_CTRL_IOCTL_MAP:
+
+		/*
+		 * The top half of HICR7 is the MSB of the BMC address of the
+		 * mapping.
+		 * The bottom half of HICR7 is the MSB of the HOST LPC
+		 * firmware space address of the mapping.
+		 *
+		 * The 1 bits in the top of half of HICR8 represent the bits
+		 * (in the requested address) that should be ignored and
+		 * replaced with those from the top half of HICR7.
+		 * The 1 bits in the bottom half of HICR8 represent the bits
+		 * (in the requested address) that should be kept and pass
+		 * into the BMC address space.
+		 */
+
+		/*
+		 * It doesn't make sense to talk about a size or offset with
+		 * low 16 bits set. Both HICR7 and HICR8 talk about the top 16
+		 * bits of addresses and sizes.
+		 */
+
+		if ((map.size & 0x0000ffff) || (map.offset & 0x0000ffff))
+			return -EINVAL;
+
+		/*
+		 * Because of the way the masks work in HICR8 offset has to
+		 * be a multiple of size.
+		 */
+		if (map.offset & (map.size - 1))
+			return -EINVAL;
+
+		if (map.window_type == ASPEED_LPC_CTRL_WINDOW_FLASH) {
+			if (!lpc_ctrl->pnor_size) {
+				dev_dbg(dev, "Didn't find host pnor flash\n");
+				return -ENXIO;
+			}
+			addr = lpc_ctrl->pnor_base;
+			size = lpc_ctrl->pnor_size;
+		} else if (map.window_type == ASPEED_LPC_CTRL_WINDOW_MEMORY) {
+			/* If memory-region is not described in device tree */
+			if (!lpc_ctrl->mem_size) {
+				dev_dbg(dev, "Didn't find reserved memory\n");
+				return -ENXIO;
+			}
+			addr = lpc_ctrl->mem_base;
+			size = lpc_ctrl->mem_size;
+		} else {
+			return -EINVAL;
+		}
+
+		/* Check overflow first! */
+		if (map.offset + map.size < map.offset ||
+			map.offset + map.size > size)
+			return -EINVAL;
+
+		if (map.size == 0 || map.size > size)
+			return -EINVAL;
+
+		addr += map.offset;
+
+		/*
+		 * addr (host lpc address) is safe regardless of values. This
+		 * simply changes the address the host has to request on its
+		 * side of the LPC bus. This cannot impact the hosts own
+		 * memory space by surprise as LPC specific accessors are
+		 * required. The only strange thing that could be done is
+		 * setting the lower 16 bits but the shift takes care of that.
+		 */
+
+		rc = regmap_write(lpc_ctrl->regmap, HICR7,
+				(addr | (map.addr >> 16)));
+		if (rc)
+			return rc;
+
+		rc = regmap_write(lpc_ctrl->regmap, HICR8,
+				(~(map.size - 1)) | ((map.size >> 16) - 1));
+		if (rc)
+			return rc;
+
+		/*
+		 * Switch to FWH2AHB mode, AST2600 only.
+		 */
+		if (lpc_ctrl->fwh2ahb) {
+			/*
+			 * Enable FWH2AHB in SCU debug control register 2. This
+			 * does not turn it on, but makes it available for it
+			 * to be configured in HICR6.
+			 */
+			regmap_update_bits(lpc_ctrl->scu, 0x0D8, BIT(2), 0);
+
+			/*
+			 * The other bits in this register are interrupt status bits
+			 * that are cleared by writing 1. As we don't want to clear
+			 * them, set only the bit of interest.
+			 */
+			regmap_write(lpc_ctrl->regmap, HICR6, SW_FWH2AHB);
+		}
+
+		/*
+		 * Enable LPC FHW cycles. This is required for the host to
+		 * access the regions specified.
+		 */
+		return regmap_update_bits(lpc_ctrl->regmap, HICR5,
+				HICR5_ENFWH | HICR5_ENL2H,
+				HICR5_ENFWH | HICR5_ENL2H);
+	}
+
+	return -EINVAL;
+}
+
+static const struct file_operations aspeed_lpc_ctrl_fops = {
+	.owner		= THIS_MODULE,
+	.mmap		= aspeed_lpc_ctrl_mmap,
+	.unlocked_ioctl	= aspeed_lpc_ctrl_ioctl,
+};
+
+static int aspeed_lpc_ctrl_probe(struct platform_device *pdev)
+{
+	struct aspeed_lpc_ctrl *lpc_ctrl;
+	struct device_node *node;
+	struct resource resm;
+	struct device *dev;
+	struct device_node *np;
+	int rc;
+
+	dev = &pdev->dev;
+
+	lpc_ctrl = devm_kzalloc(dev, sizeof(*lpc_ctrl), GFP_KERNEL);
+	if (!lpc_ctrl)
+		return -ENOMEM;
+
+	/* If flash is described in device tree then store */
+	node = of_parse_phandle(dev->of_node, "flash", 0);
+	if (!node) {
+		dev_dbg(dev, "Didn't find host pnor flash node\n");
+	} else {
+		rc = of_address_to_resource(node, 1, &resm);
+		of_node_put(node);
+		if (rc) {
+			dev_err(dev, "Couldn't address to resource for flash\n");
+			return rc;
+		}
+
+		lpc_ctrl->pnor_size = resource_size(&resm);
+		lpc_ctrl->pnor_base = resm.start;
+	}
+
+
+	dev_set_drvdata(&pdev->dev, lpc_ctrl);
+
+	/* If memory-region is described in device tree then store */
+	rc = of_reserved_mem_region_to_resource(dev->of_node, 0, &resm);
+	if (!rc) {
+		lpc_ctrl->mem_size = resource_size(&resm);
+		lpc_ctrl->mem_base = resm.start;
+
+		if (!is_power_of_2(lpc_ctrl->mem_size)) {
+			dev_err(dev, "Reserved memory size must be a power of 2, got %u\n",
+			       (unsigned int)lpc_ctrl->mem_size);
+			return -EINVAL;
+		}
+
+		if (!IS_ALIGNED(lpc_ctrl->mem_base, lpc_ctrl->mem_size)) {
+			dev_err(dev, "Reserved memory must be naturally aligned for size %u\n",
+			       (unsigned int)lpc_ctrl->mem_size);
+			return -EINVAL;
+		}
+	}
+
+	np = pdev->dev.parent->of_node;
+	if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
+	    !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
+	    !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
+		dev_err(dev, "unsupported LPC device binding\n");
+		return -ENODEV;
+	}
+
+	lpc_ctrl->regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(lpc_ctrl->regmap)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	if (of_device_is_compatible(dev->of_node, "aspeed,ast2600-lpc-ctrl")) {
+		lpc_ctrl->fwh2ahb = true;
+
+		lpc_ctrl->scu = syscon_regmap_lookup_by_compatible("aspeed,ast2600-scu");
+		if (IS_ERR(lpc_ctrl->scu)) {
+			dev_err(dev, "couldn't find scu\n");
+			return PTR_ERR(lpc_ctrl->scu);
+		}
+	}
+
+	lpc_ctrl->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(lpc_ctrl->clk))
+		return dev_err_probe(dev, PTR_ERR(lpc_ctrl->clk),
+				     "couldn't get clock\n");
+	rc = clk_prepare_enable(lpc_ctrl->clk);
+	if (rc) {
+		dev_err(dev, "couldn't enable clock\n");
+		return rc;
+	}
+
+	lpc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
+	lpc_ctrl->miscdev.name = DEVICE_NAME;
+	lpc_ctrl->miscdev.fops = &aspeed_lpc_ctrl_fops;
+	lpc_ctrl->miscdev.parent = dev;
+	rc = misc_register(&lpc_ctrl->miscdev);
+	if (rc) {
+		dev_err(dev, "Unable to register device\n");
+		goto err;
+	}
+
+	return 0;
+
+err:
+	clk_disable_unprepare(lpc_ctrl->clk);
+	return rc;
+}
+
+static void aspeed_lpc_ctrl_remove(struct platform_device *pdev)
+{
+	struct aspeed_lpc_ctrl *lpc_ctrl = dev_get_drvdata(&pdev->dev);
+
+	misc_deregister(&lpc_ctrl->miscdev);
+	clk_disable_unprepare(lpc_ctrl->clk);
+}
+
+static const struct of_device_id aspeed_lpc_ctrl_match[] = {
+	{ .compatible = "aspeed,ast2400-lpc-ctrl" },
+	{ .compatible = "aspeed,ast2500-lpc-ctrl" },
+	{ .compatible = "aspeed,ast2600-lpc-ctrl" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, aspeed_lpc_ctrl_match);
+
+static struct platform_driver aspeed_lpc_ctrl_driver = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table = aspeed_lpc_ctrl_match,
+	},
+	.probe = aspeed_lpc_ctrl_probe,
+	.remove = aspeed_lpc_ctrl_remove,
+};
+
+module_platform_driver(aspeed_lpc_ctrl_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Cyril Bur <cyrilbur@gmail.com>");
+MODULE_DESCRIPTION("Control for ASPEED LPC HOST to BMC mappings");
diff --git a/drivers/soc/aspeed/aspeed-lpc-snoop.c b/drivers/soc/aspeed/aspeed-lpc-snoop.c
new file mode 100644
index 000000000..b09dca340
--- /dev/null
+++ b/drivers/soc/aspeed/aspeed-lpc-snoop.c
@@ -0,0 +1,398 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2017 Google Inc
+ *
+ * Provides a simple driver to control the ASPEED LPC snoop interface which
+ * allows the BMC to listen on and save the data written by
+ * the host to an arbitrary LPC I/O port.
+ *
+ * Typically used by the BMC to "watch" host boot progress via port
+ * 0x80 writes made by the BIOS during the boot process.
+ */
+
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/clk.h>
+#include <linux/dev_printk.h>
+#include <linux/interrupt.h>
+#include <linux/fs.h>
+#include <linux/kfifo.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/regmap.h>
+
+#define DEVICE_NAME	"aspeed-lpc-snoop"
+
+#define SNOOP_FIFO_SIZE 2048
+
+#define HICR5	0x80
+#define HICR5_EN_SNP0W		BIT(0)
+#define HICR5_ENINT_SNP0W	BIT(1)
+#define HICR5_EN_SNP1W		BIT(2)
+#define HICR5_ENINT_SNP1W	BIT(3)
+#define HICR6	0x84
+#define HICR6_STR_SNP0W		BIT(0)
+#define HICR6_STR_SNP1W		BIT(1)
+#define SNPWADR	0x90
+#define SNPWADR_CH0_MASK	GENMASK(15, 0)
+#define SNPWADR_CH0_SHIFT	0
+#define SNPWADR_CH1_MASK	GENMASK(31, 16)
+#define SNPWADR_CH1_SHIFT	16
+#define SNPWDR	0x94
+#define SNPWDR_CH0_MASK		GENMASK(7, 0)
+#define SNPWDR_CH0_SHIFT	0
+#define SNPWDR_CH1_MASK		GENMASK(15, 8)
+#define SNPWDR_CH1_SHIFT	8
+#define HICRB	0x100
+#define HICRB_ENSNP0D		BIT(14)
+#define HICRB_ENSNP1D		BIT(15)
+
+struct aspeed_lpc_snoop_model_data {
+	/* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
+	 * can use them.
+	 */
+	unsigned int has_hicrb_ensnp;
+};
+
+enum aspeed_lpc_snoop_index {
+	ASPEED_LPC_SNOOP_INDEX_0 = 0,
+	ASPEED_LPC_SNOOP_INDEX_1 = 1,
+	ASPEED_LPC_SNOOP_INDEX_MAX = ASPEED_LPC_SNOOP_INDEX_1,
+};
+
+struct aspeed_lpc_snoop_channel_cfg {
+	enum aspeed_lpc_snoop_index index;
+	u32 hicr5_en;
+	u32 snpwadr_mask;
+	u32 snpwadr_shift;
+	u32 hicrb_en;
+};
+
+struct aspeed_lpc_snoop_channel {
+	const struct aspeed_lpc_snoop_channel_cfg *cfg;
+	bool enabled;
+	spinlock_t		lock;
+	struct kfifo		fifo __guarded_by(&lock);
+	wait_queue_head_t	wq;
+	struct miscdevice	miscdev;
+};
+
+struct aspeed_lpc_snoop {
+	struct regmap		*regmap;
+	int			irq;
+	struct clk		*clk;
+	struct aspeed_lpc_snoop_channel chan[ASPEED_LPC_SNOOP_INDEX_MAX + 1];
+};
+
+static const struct aspeed_lpc_snoop_channel_cfg channel_cfgs[ASPEED_LPC_SNOOP_INDEX_MAX + 1] = {
+	{
+		.index = ASPEED_LPC_SNOOP_INDEX_0,
+		.hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
+		.snpwadr_mask = SNPWADR_CH0_MASK,
+		.snpwadr_shift = SNPWADR_CH0_SHIFT,
+		.hicrb_en = HICRB_ENSNP0D,
+	},
+	{
+		.index = ASPEED_LPC_SNOOP_INDEX_1,
+		.hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
+		.snpwadr_mask = SNPWADR_CH1_MASK,
+		.snpwadr_shift = SNPWADR_CH1_SHIFT,
+		.hicrb_en = HICRB_ENSNP1D,
+	},
+};
+
+static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
+{
+	return container_of(file->private_data,
+			    struct aspeed_lpc_snoop_channel,
+			    miscdev);
+}
+
+static ssize_t snoop_file_read(struct file *file, char __user *buffer,
+				size_t count, loff_t *ppos)
+{
+	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
+	u8 *buf __free(kfree) = NULL;
+	unsigned int copied;
+	int ret = 0;
+
+	if (kfifo_is_empty(&chan->fifo)) {
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		ret = wait_event_interruptible(chan->wq,
+				!kfifo_is_empty(&chan->fifo));
+		if (ret == -ERESTARTSYS)
+			return -EINTR;
+	}
+
+	count = min_t(size_t, count, SNOOP_FIFO_SIZE);
+
+	buf = kmalloc(count, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	copied = kfifo_out_spinlocked(&chan->fifo, buf, count, &chan->lock);
+	if (copied && copy_to_user(buffer, buf, copied))
+		return -EFAULT;
+
+	return copied;
+}
+
+static __poll_t snoop_file_poll(struct file *file,
+				    struct poll_table_struct *pt)
+{
+	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
+
+	poll_wait(file, &chan->wq, pt);
+	return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
+}
+
+static const struct file_operations snoop_fops = {
+	.owner  = THIS_MODULE,
+	.read   = snoop_file_read,
+	.poll   = snoop_file_poll,
+	.llseek = noop_llseek,
+};
+
+/* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
+static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
+{
+	scoped_guard(spinlock, &chan->lock) {
+		if (!kfifo_initialized(&chan->fifo))
+			return;
+		if (kfifo_is_full(&chan->fifo))
+			kfifo_skip(&chan->fifo);
+		kfifo_put(&chan->fifo, val);
+	}
+	wake_up_interruptible(&chan->wq);
+}
+
+static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
+{
+	struct aspeed_lpc_snoop *lpc_snoop = arg;
+	u32 reg, data;
+
+	if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
+		return IRQ_NONE;
+
+	/* Check if one of the snoop channels is interrupting */
+	reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
+	if (!reg)
+		return IRQ_NONE;
+
+	/* Ack pending IRQs */
+	regmap_write(lpc_snoop->regmap, HICR6, reg);
+
+	/* Read and save most recent snoop'ed data byte to FIFO */
+	regmap_read(lpc_snoop->regmap, SNPWDR, &data);
+
+	if (reg & HICR6_STR_SNP0W) {
+		u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
+
+		put_fifo_with_discard(&lpc_snoop->chan[0], val);
+	}
+	if (reg & HICR6_STR_SNP1W) {
+		u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
+
+		put_fifo_with_discard(&lpc_snoop->chan[1], val);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
+				       struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int rc;
+
+	lpc_snoop->irq = platform_get_irq(pdev, 0);
+	if (lpc_snoop->irq < 0)
+		return -ENODEV;
+
+	rc = devm_request_irq(dev, lpc_snoop->irq,
+			      aspeed_lpc_snoop_irq, IRQF_SHARED,
+			      DEVICE_NAME, lpc_snoop);
+	if (rc < 0) {
+		dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
+		lpc_snoop->irq = 0;
+		return rc;
+	}
+
+	return 0;
+}
+
+__attribute__((nonnull))
+static int aspeed_lpc_enable_snoop(struct device *dev,
+				    struct aspeed_lpc_snoop *lpc_snoop,
+				    struct aspeed_lpc_snoop_channel *channel,
+				    const struct aspeed_lpc_snoop_channel_cfg *cfg,
+				    u16 lpc_port)
+{
+	const struct aspeed_lpc_snoop_model_data *model_data;
+	int rc = 0;
+
+	if (WARN_ON(channel->enabled))
+		return -EBUSY;
+
+	init_waitqueue_head(&channel->wq);
+
+	channel->cfg = cfg;
+	channel->miscdev.minor = MISC_DYNAMIC_MINOR;
+	channel->miscdev.fops = &snoop_fops;
+	channel->miscdev.parent = dev;
+
+	channel->miscdev.name =
+		devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, cfg->index);
+	if (!channel->miscdev.name)
+		return -ENOMEM;
+
+	scoped_guard(spinlock_init, &channel->lock) {
+		rc = kfifo_alloc(&channel->fifo, SNOOP_FIFO_SIZE, GFP_KERNEL);
+		if (rc)
+			return rc;
+	}
+
+	rc = misc_register(&channel->miscdev);
+	if (rc)
+		goto err_free_fifo;
+
+	/* Enable LPC snoop channel at requested port */
+	regmap_set_bits(lpc_snoop->regmap, HICR5, cfg->hicr5_en);
+	regmap_update_bits(lpc_snoop->regmap, SNPWADR, cfg->snpwadr_mask,
+			   lpc_port << cfg->snpwadr_shift);
+
+	model_data = of_device_get_match_data(dev);
+	if (model_data && model_data->has_hicrb_ensnp)
+		regmap_set_bits(lpc_snoop->regmap, HICRB, cfg->hicrb_en);
+
+	channel->enabled = true;
+
+	return 0;
+
+err_free_fifo:
+	kfifo_free(&channel->fifo);
+	return rc;
+}
+
+__attribute__((nonnull))
+static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
+				     struct aspeed_lpc_snoop_channel *channel)
+{
+	if (!channel->enabled)
+		return;
+
+	/* Disable interrupts along with the device */
+	regmap_clear_bits(lpc_snoop->regmap, HICR5, channel->cfg->hicr5_en);
+
+	channel->enabled = false;
+	/* Consider improving safety wrt concurrent reader(s) */
+	misc_deregister(&channel->miscdev);
+	kfifo_free(&channel->fifo);
+}
+
+static void aspeed_lpc_snoop_remove(struct platform_device *pdev)
+{
+	struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
+
+	/* Disable both snoop channels */
+	aspeed_lpc_disable_snoop(lpc_snoop, &lpc_snoop->chan[0]);
+	aspeed_lpc_disable_snoop(lpc_snoop, &lpc_snoop->chan[1]);
+}
+
+static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
+{
+	struct aspeed_lpc_snoop *lpc_snoop;
+	struct device_node *np;
+	struct device *dev;
+	int idx;
+	int rc;
+
+	dev = &pdev->dev;
+
+	lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
+	if (!lpc_snoop)
+		return -ENOMEM;
+
+	np = pdev->dev.parent->of_node;
+	if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
+	    !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
+	    !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
+		dev_err(dev, "unsupported LPC device binding\n");
+		return -ENODEV;
+	}
+
+	lpc_snoop->regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(lpc_snoop->regmap))
+		return dev_err_probe(dev, PTR_ERR(lpc_snoop->regmap), "Couldn't get regmap\n");
+
+	dev_set_drvdata(&pdev->dev, lpc_snoop);
+
+	lpc_snoop->clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(lpc_snoop->clk))
+		return dev_err_probe(dev, PTR_ERR(lpc_snoop->clk), "couldn't get clock");
+
+	rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
+	if (rc)
+		return rc;
+
+	static_assert(ARRAY_SIZE(channel_cfgs) == ARRAY_SIZE(lpc_snoop->chan),
+		"Broken implementation assumption regarding cfg count");
+	for (idx = ASPEED_LPC_SNOOP_INDEX_0; idx <= ASPEED_LPC_SNOOP_INDEX_MAX; idx++) {
+		u32 port;
+
+		rc = of_property_read_u32_index(dev->of_node, "snoop-ports", idx, &port);
+		if (rc)
+			break;
+
+		rc = aspeed_lpc_enable_snoop(dev, lpc_snoop, &lpc_snoop->chan[idx],
+					     &channel_cfgs[idx], port);
+		if (rc)
+			goto cleanup_channels;
+	}
+
+	return idx == ASPEED_LPC_SNOOP_INDEX_0 ? -ENODEV : 0;
+
+cleanup_channels:
+	aspeed_lpc_snoop_remove(pdev);
+
+	return rc;
+}
+
+static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
+	.has_hicrb_ensnp = 0,
+};
+
+static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
+	.has_hicrb_ensnp = 1,
+};
+
+static const struct of_device_id aspeed_lpc_snoop_match[] = {
+	{ .compatible = "aspeed,ast2400-lpc-snoop",
+	  .data = &ast2400_model_data },
+	{ .compatible = "aspeed,ast2500-lpc-snoop",
+	  .data = &ast2500_model_data },
+	{ .compatible = "aspeed,ast2600-lpc-snoop",
+	  .data = &ast2500_model_data },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
+
+static struct platform_driver aspeed_lpc_snoop_driver = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table = aspeed_lpc_snoop_match,
+	},
+	.probe = aspeed_lpc_snoop_probe,
+	.remove = aspeed_lpc_snoop_remove,
+};
+
+module_platform_driver(aspeed_lpc_snoop_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
+MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
diff --git a/drivers/soc/aspeed/aspeed-p2a-ctrl.c b/drivers/soc/aspeed/aspeed-p2a-ctrl.c
new file mode 100644
index 000000000..b6b7b80f8
--- /dev/null
+++ b/drivers/soc/aspeed/aspeed-p2a-ctrl.c
@@ -0,0 +1,434 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2019 Google Inc
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * Provides a simple driver to control the ASPEED P2A interface which allows
+ * the host to read and write to various regions of the BMC's memory.
+ */
+
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <linux/aspeed-p2a-ctrl.h>
+
+#define DEVICE_NAME	"aspeed-p2a-ctrl"
+
+/* SCU2C is a Misc. Control Register. */
+#define SCU2C 0x2c
+/* SCU180 is the PCIe Configuration Setting Control Register. */
+#define SCU180 0x180
+/* Bit 1 controls the P2A bridge, while bit 0 controls the entire VGA device
+ * on the PCI bus.
+ */
+#define SCU180_ENP2A BIT(1)
+
+/* The ast2400/2500 both have six ranges. */
+#define P2A_REGION_COUNT 6
+
+struct region {
+	u64 min;
+	u64 max;
+	u32 bit;
+};
+
+struct aspeed_p2a_model_data {
+	/* min, max, bit */
+	struct region regions[P2A_REGION_COUNT];
+};
+
+struct aspeed_p2a_ctrl {
+	struct miscdevice miscdev;
+	struct regmap *regmap;
+
+	const struct aspeed_p2a_model_data *config;
+
+	/* Access to these needs to be locked, held via probe, mapping ioctl,
+	 * and release, remove.
+	 */
+	struct mutex tracking;
+	u32 readers;
+	u32 readerwriters[P2A_REGION_COUNT];
+
+	phys_addr_t mem_base;
+	resource_size_t mem_size;
+};
+
+struct aspeed_p2a_user {
+	struct file *file;
+	struct aspeed_p2a_ctrl *parent;
+
+	/* The entire memory space is opened for reading once the bridge is
+	 * enabled, therefore this needs only to be tracked once per user.
+	 * If any user has it open for read, the bridge must stay enabled.
+	 */
+	u32 read;
+
+	/* Each entry of the array corresponds to a P2A Region.  If the user
+	 * opens for read or readwrite, the reference goes up here.  On
+	 * release, this array is walked and references adjusted accordingly.
+	 */
+	u32 readwrite[P2A_REGION_COUNT];
+};
+
+static void aspeed_p2a_enable_bridge(struct aspeed_p2a_ctrl *p2a_ctrl)
+{
+	regmap_update_bits(p2a_ctrl->regmap,
+		SCU180, SCU180_ENP2A, SCU180_ENP2A);
+}
+
+static void aspeed_p2a_disable_bridge(struct aspeed_p2a_ctrl *p2a_ctrl)
+{
+	regmap_update_bits(p2a_ctrl->regmap, SCU180, SCU180_ENP2A, 0);
+}
+
+static int aspeed_p2a_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long vsize;
+	pgprot_t prot;
+	struct aspeed_p2a_user *priv = file->private_data;
+	struct aspeed_p2a_ctrl *ctrl = priv->parent;
+
+	if (ctrl->mem_base == 0 && ctrl->mem_size == 0)
+		return -EINVAL;
+
+	vsize = vma->vm_end - vma->vm_start;
+	prot = vma->vm_page_prot;
+
+	if (vma->vm_pgoff + vma_pages(vma) > ctrl->mem_size >> PAGE_SHIFT)
+		return -EINVAL;
+
+	/* ast2400/2500 AHB accesses are not cache coherent */
+	prot = pgprot_noncached(prot);
+
+	if (remap_pfn_range(vma, vma->vm_start,
+		(ctrl->mem_base >> PAGE_SHIFT) + vma->vm_pgoff,
+		vsize, prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static bool aspeed_p2a_region_acquire(struct aspeed_p2a_user *priv,
+		struct aspeed_p2a_ctrl *ctrl,
+		struct aspeed_p2a_ctrl_mapping *map)
+{
+	int i;
+	u64 base, end;
+	bool matched = false;
+
+	base = map->addr;
+	end = map->addr + (map->length - 1);
+
+	/* If the value is a legal u32, it will find a match. */
+	for (i = 0; i < P2A_REGION_COUNT; i++) {
+		const struct region *curr = &ctrl->config->regions[i];
+
+		/* If the top of this region is lower than your base, skip it.
+		 */
+		if (curr->max < base)
+			continue;
+
+		/* If the bottom of this region is higher than your end, bail.
+		 */
+		if (curr->min > end)
+			break;
+
+		/* Lock this and update it, therefore it someone else is
+		 * closing their file out, this'll preserve the increment.
+		 */
+		mutex_lock(&ctrl->tracking);
+		ctrl->readerwriters[i] += 1;
+		mutex_unlock(&ctrl->tracking);
+
+		/* Track with the user, so when they close their file, we can
+		 * decrement properly.
+		 */
+		priv->readwrite[i] += 1;
+
+		/* Enable the region as read-write. */
+		regmap_update_bits(ctrl->regmap, SCU2C, curr->bit, 0);
+		matched = true;
+	}
+
+	return matched;
+}
+
+static long aspeed_p2a_ioctl(struct file *file, unsigned int cmd,
+		unsigned long data)
+{
+	struct aspeed_p2a_user *priv = file->private_data;
+	struct aspeed_p2a_ctrl *ctrl = priv->parent;
+	void __user *arg = (void __user *)data;
+	struct aspeed_p2a_ctrl_mapping map;
+
+	if (copy_from_user(&map, arg, sizeof(map)))
+		return -EFAULT;
+
+	switch (cmd) {
+	case ASPEED_P2A_CTRL_IOCTL_SET_WINDOW:
+		/* If they want a region to be read-only, since the entire
+		 * region is read-only once enabled, we just need to track this
+		 * user wants to read from the bridge, and if it's not enabled.
+		 * Enable it.
+		 */
+		if (map.flags == ASPEED_P2A_CTRL_READ_ONLY) {
+			mutex_lock(&ctrl->tracking);
+			ctrl->readers += 1;
+			mutex_unlock(&ctrl->tracking);
+
+			/* Track with the user, so when they close their file,
+			 * we can decrement properly.
+			 */
+			priv->read += 1;
+		} else if (map.flags == ASPEED_P2A_CTRL_READWRITE) {
+			/* If we don't acquire any region return error. */
+			if (!aspeed_p2a_region_acquire(priv, ctrl, &map)) {
+				return -EINVAL;
+			}
+		} else {
+			/* Invalid map flags. */
+			return -EINVAL;
+		}
+
+		aspeed_p2a_enable_bridge(ctrl);
+		return 0;
+	case ASPEED_P2A_CTRL_IOCTL_GET_MEMORY_CONFIG:
+		/* This is a request for the memory-region and corresponding
+		 * length that is used by the driver for mmap.
+		 */
+
+		map.flags = 0;
+		map.addr = ctrl->mem_base;
+		map.length = ctrl->mem_size;
+
+		return copy_to_user(arg, &map, sizeof(map)) ? -EFAULT : 0;
+	}
+
+	return -EINVAL;
+}
+
+
+/*
+ * When a user opens this file, we create a structure to track their mappings.
+ *
+ * A user can map a region as read-only (bridge enabled), or read-write (bit
+ * flipped, and bridge enabled).  Either way, this tracking is used, s.t. when
+ * they release the device references are handled.
+ *
+ * The bridge is not enabled until a user calls an ioctl to map a region,
+ * simply opening the device does not enable it.
+ */
+static int aspeed_p2a_open(struct inode *inode, struct file *file)
+{
+	struct aspeed_p2a_user *priv;
+
+	priv = kmalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->file = file;
+	priv->read = 0;
+	memset(priv->readwrite, 0, sizeof(priv->readwrite));
+
+	/* The file's private_data is initialized to the p2a_ctrl. */
+	priv->parent = file->private_data;
+
+	/* Set the file's private_data to the user's data. */
+	file->private_data = priv;
+
+	return 0;
+}
+
+/*
+ * This will close the users mappings.  It will go through what they had opened
+ * for readwrite, and decrement those counts.  If at the end, this is the last
+ * user, it'll close the bridge.
+ */
+static int aspeed_p2a_release(struct inode *inode, struct file *file)
+{
+	int i;
+	u32 bits = 0;
+	bool open_regions = false;
+	struct aspeed_p2a_user *priv = file->private_data;
+
+	/* Lock others from changing these values until everything is updated
+	 * in one pass.
+	 */
+	mutex_lock(&priv->parent->tracking);
+
+	priv->parent->readers -= priv->read;
+
+	for (i = 0; i < P2A_REGION_COUNT; i++) {
+		priv->parent->readerwriters[i] -= priv->readwrite[i];
+
+		if (priv->parent->readerwriters[i] > 0)
+			open_regions = true;
+		else
+			bits |= priv->parent->config->regions[i].bit;
+	}
+
+	/* Setting a bit to 1 disables the region, so let's just OR with the
+	 * above to disable any.
+	 */
+
+	/* Note, if another user is trying to ioctl, they can't grab tracking,
+	 * and therefore can't grab either register mutex.
+	 * If another user is trying to close, they can't grab tracking either.
+	 */
+	regmap_update_bits(priv->parent->regmap, SCU2C, bits, bits);
+
+	/* If parent->readers is zero and open windows is 0, disable the
+	 * bridge.
+	 */
+	if (!open_regions && priv->parent->readers == 0)
+		aspeed_p2a_disable_bridge(priv->parent);
+
+	mutex_unlock(&priv->parent->tracking);
+
+	kfree(priv);
+
+	return 0;
+}
+
+static const struct file_operations aspeed_p2a_ctrl_fops = {
+	.owner = THIS_MODULE,
+	.mmap = aspeed_p2a_mmap,
+	.unlocked_ioctl = aspeed_p2a_ioctl,
+	.open = aspeed_p2a_open,
+	.release = aspeed_p2a_release,
+};
+
+/* The regions are controlled by SCU2C */
+static void aspeed_p2a_disable_all(struct aspeed_p2a_ctrl *p2a_ctrl)
+{
+	int i;
+	u32 value = 0;
+
+	for (i = 0; i < P2A_REGION_COUNT; i++)
+		value |= p2a_ctrl->config->regions[i].bit;
+
+	regmap_update_bits(p2a_ctrl->regmap, SCU2C, value, value);
+
+	/* Disable the bridge. */
+	aspeed_p2a_disable_bridge(p2a_ctrl);
+}
+
+static int aspeed_p2a_ctrl_probe(struct platform_device *pdev)
+{
+	struct aspeed_p2a_ctrl *misc_ctrl;
+	struct device *dev;
+	struct resource resm;
+	int rc = 0;
+
+	dev = &pdev->dev;
+
+	misc_ctrl = devm_kzalloc(dev, sizeof(*misc_ctrl), GFP_KERNEL);
+	if (!misc_ctrl)
+		return -ENOMEM;
+
+	mutex_init(&misc_ctrl->tracking);
+
+	/* optional. */
+	rc = of_reserved_mem_region_to_resource(dev->of_node, 0, &resm);
+	if (!rc) {
+		misc_ctrl->mem_size = resource_size(&resm);
+		misc_ctrl->mem_base = resm.start;
+	}
+
+	misc_ctrl->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(misc_ctrl->regmap)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	misc_ctrl->config = of_device_get_match_data(dev);
+
+	dev_set_drvdata(&pdev->dev, misc_ctrl);
+
+	aspeed_p2a_disable_all(misc_ctrl);
+
+	misc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
+	misc_ctrl->miscdev.name = DEVICE_NAME;
+	misc_ctrl->miscdev.fops = &aspeed_p2a_ctrl_fops;
+	misc_ctrl->miscdev.parent = dev;
+
+	rc = misc_register(&misc_ctrl->miscdev);
+	if (rc)
+		dev_err(dev, "Unable to register device\n");
+
+	return rc;
+}
+
+static void aspeed_p2a_ctrl_remove(struct platform_device *pdev)
+{
+	struct aspeed_p2a_ctrl *p2a_ctrl = dev_get_drvdata(&pdev->dev);
+
+	misc_deregister(&p2a_ctrl->miscdev);
+}
+
+#define SCU2C_DRAM	BIT(25)
+#define SCU2C_SPI	BIT(24)
+#define SCU2C_SOC	BIT(23)
+#define SCU2C_FLASH	BIT(22)
+
+static const struct aspeed_p2a_model_data ast2400_model_data = {
+	.regions = {
+		{0x00000000, 0x17FFFFFF, SCU2C_FLASH},
+		{0x18000000, 0x1FFFFFFF, SCU2C_SOC},
+		{0x20000000, 0x2FFFFFFF, SCU2C_FLASH},
+		{0x30000000, 0x3FFFFFFF, SCU2C_SPI},
+		{0x40000000, 0x5FFFFFFF, SCU2C_DRAM},
+		{0x60000000, 0xFFFFFFFF, SCU2C_SOC},
+	}
+};
+
+static const struct aspeed_p2a_model_data ast2500_model_data = {
+	.regions = {
+		{0x00000000, 0x0FFFFFFF, SCU2C_FLASH},
+		{0x10000000, 0x1FFFFFFF, SCU2C_SOC},
+		{0x20000000, 0x3FFFFFFF, SCU2C_FLASH},
+		{0x40000000, 0x5FFFFFFF, SCU2C_SOC},
+		{0x60000000, 0x7FFFFFFF, SCU2C_SPI},
+		{0x80000000, 0xFFFFFFFF, SCU2C_DRAM},
+	}
+};
+
+static const struct of_device_id aspeed_p2a_ctrl_match[] = {
+	{ .compatible = "aspeed,ast2400-p2a-ctrl",
+	  .data = &ast2400_model_data },
+	{ .compatible = "aspeed,ast2500-p2a-ctrl",
+	  .data = &ast2500_model_data },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, aspeed_p2a_ctrl_match);
+
+static struct platform_driver aspeed_p2a_ctrl_driver = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table = aspeed_p2a_ctrl_match,
+	},
+	.probe = aspeed_p2a_ctrl_probe,
+	.remove = aspeed_p2a_ctrl_remove,
+};
+
+module_platform_driver(aspeed_p2a_ctrl_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Patrick Venture <venture@google.com>");
+MODULE_DESCRIPTION("Control for aspeed 2400/2500 P2A VGA HOST to BMC mappings");
diff --git a/drivers/soc/aspeed/aspeed-socinfo.c b/drivers/soc/aspeed/aspeed-socinfo.c
new file mode 100644
index 000000000..fb8fde94b
--- /dev/null
+++ b/drivers/soc/aspeed/aspeed-socinfo.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright 2019 IBM Corp. */
+
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+
+static struct {
+	const char *name;
+	const u32 id;
+} const rev_table[] = {
+	/* AST2400 */
+	{ "AST2400", 0x02000303 },
+	{ "AST1400", 0x02010103 },
+	{ "AST1250", 0x02010303 },
+	/* AST2500 */
+	{ "AST2500", 0x04000303 },
+	{ "AST2510", 0x04000103 },
+	{ "AST2520", 0x04000203 },
+	{ "AST2530", 0x04000403 },
+	/* AST2600 */
+	{ "AST2600", 0x05000303 },
+	{ "AST2620", 0x05010203 },
+	{ "AST2605", 0x05030103 },
+	{ "AST2625", 0x05030403 },
+	/* AST2700 */
+	{ "AST2750", 0x06000003 },
+	{ "AST2700", 0x06000103 },
+	{ "AST2720", 0x06000203 },
+};
+
+static const char *siliconid_to_name(u32 siliconid)
+{
+	unsigned int id = siliconid & 0xff00ffff;
+	unsigned int i;
+
+	for (i = 0 ; i < ARRAY_SIZE(rev_table) ; ++i) {
+		if ((rev_table[i].id & 0xff00ffff) == id)
+			return rev_table[i].name;
+	}
+
+	return "Unknown";
+}
+
+static const char *siliconid_to_rev(u32 siliconid)
+{
+	unsigned int rev = (siliconid >> 16) & 0xff;
+	unsigned int gen = (siliconid >> 24) & 0xff;
+
+	if (gen < 0x5) {
+		/* AST2500 and below */
+		switch (rev) {
+		case 0:
+			return "A0";
+		case 1:
+			return "A1";
+		case 3:
+			return "A2";
+		}
+	} else {
+		/* AST2600 */
+		switch (rev) {
+		case 0:
+			return "A0";
+		case 1:
+			return "A1";
+		case 2:
+			return "A2";
+		case 3:
+			return "A3";
+		}
+	}
+
+	return "??";
+}
+
+static int __init aspeed_socinfo_init(void)
+{
+	struct soc_device_attribute *attrs;
+	struct soc_device *soc_dev;
+	struct device_node *np;
+	void __iomem *reg;
+	bool has_chipid = false;
+	u32 siliconid;
+	u32 chipid[2];
+	const char *machine = NULL;
+
+	np = of_find_compatible_node(NULL, NULL, "aspeed,silicon-id");
+	if (!of_device_is_available(np)) {
+		of_node_put(np);
+		return -ENODEV;
+	}
+
+	reg = of_iomap(np, 0);
+	if (!reg) {
+		of_node_put(np);
+		return -ENODEV;
+	}
+	siliconid = readl(reg);
+	iounmap(reg);
+
+	/* This is optional, the ast2400 does not have it */
+	reg = of_iomap(np, 1);
+	if (reg) {
+		has_chipid = true;
+		chipid[0] = readl(reg);
+		chipid[1] = readl(reg + 4);
+		iounmap(reg);
+	}
+	of_node_put(np);
+
+	attrs = kzalloc_obj(*attrs);
+	if (!attrs)
+		return -ENODEV;
+
+	/*
+	 * Machine: Romulus BMC
+	 * Family: AST2500
+	 * Revision: A1
+	 * SoC ID: raw silicon revision id
+	 * Serial Number: 64-bit chipid
+	 */
+
+	np = of_find_node_by_path("/");
+	of_property_read_string(np, "model", &machine);
+	if (machine)
+		attrs->machine = kstrdup(machine, GFP_KERNEL);
+	of_node_put(np);
+
+	attrs->family = siliconid_to_name(siliconid);
+	attrs->revision = siliconid_to_rev(siliconid);
+	attrs->soc_id = kasprintf(GFP_KERNEL, "%08x", siliconid);
+
+	if (has_chipid)
+		attrs->serial_number = kasprintf(GFP_KERNEL, "%08x%08x",
+						 chipid[1], chipid[0]);
+
+	soc_dev = soc_device_register(attrs);
+	if (IS_ERR(soc_dev)) {
+		kfree(attrs->machine);
+		kfree(attrs->soc_id);
+		kfree(attrs->serial_number);
+		kfree(attrs);
+		return PTR_ERR(soc_dev);
+	}
+
+	pr_info("ASPEED %s rev %s (%s)\n",
+			attrs->family,
+			attrs->revision,
+			attrs->soc_id);
+
+	return 0;
+}
+early_initcall(aspeed_socinfo_init);
diff --git a/drivers/soc/aspeed/aspeed-uart-routing.c b/drivers/soc/aspeed/aspeed-uart-routing.c
new file mode 100644
index 000000000..b4b521b5d
--- /dev/null
+++ b/drivers/soc/aspeed/aspeed-uart-routing.c
@@ -0,0 +1,601 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2018 Google LLC
+ * Copyright (c) 2021 Aspeed Technology Inc.
+ */
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/platform_device.h>
+
+/* register offsets */
+#define HICR9	0x98
+#define HICRA	0x9c
+
+/* attributes options */
+#define UART_ROUTING_IO1	"io1"
+#define UART_ROUTING_IO2	"io2"
+#define UART_ROUTING_IO3	"io3"
+#define UART_ROUTING_IO4	"io4"
+#define UART_ROUTING_IO5	"io5"
+#define UART_ROUTING_IO6	"io6"
+#define UART_ROUTING_IO10	"io10"
+#define UART_ROUTING_UART1	"uart1"
+#define UART_ROUTING_UART2	"uart2"
+#define UART_ROUTING_UART3	"uart3"
+#define UART_ROUTING_UART4	"uart4"
+#define UART_ROUTING_UART5	"uart5"
+#define UART_ROUTING_UART6	"uart6"
+#define UART_ROUTING_UART10	"uart10"
+#define UART_ROUTING_RES	"reserved"
+
+struct aspeed_uart_routing {
+	struct regmap *map;
+	struct attribute_group const *attr_grp;
+};
+
+struct aspeed_uart_routing_selector {
+	struct device_attribute	dev_attr;
+	uint8_t reg;
+	uint8_t mask;
+	uint8_t shift;
+	const char *const options[];
+};
+
+#define to_routing_selector(_dev_attr)					\
+	container_of(_dev_attr, struct aspeed_uart_routing_selector, dev_attr)
+
+static ssize_t aspeed_uart_routing_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf);
+
+static ssize_t aspeed_uart_routing_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count);
+
+#define ROUTING_ATTR(_name) {					\
+	.attr = {.name = _name,					\
+		 .mode = VERIFY_OCTAL_PERMISSIONS(0644) },	\
+	.show = aspeed_uart_routing_show,			\
+	.store = aspeed_uart_routing_store,			\
+}
+
+/* routing selector for AST25xx */
+static struct aspeed_uart_routing_selector ast2500_io6_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO6),
+	.reg = HICR9,
+	.shift = 8,
+	.mask = 0xf,
+	.options = {
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART5,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO5,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_uart5_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART5),
+	.reg = HICRA,
+	.shift = 28,
+	.mask = 0xf,
+	.options = {
+		    UART_ROUTING_IO5,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_uart4_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART4),
+	.reg = HICRA,
+	.shift = 25,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_IO6,
+		    NULL,
+	},
+};
+
+static struct aspeed_uart_routing_selector ast2500_uart3_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART3),
+	.reg = HICRA,
+	.shift = 22,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_uart2_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART2),
+	.reg = HICRA,
+	.shift = 19,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_uart1_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART1),
+	.reg = HICRA,
+	.shift = 16,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_io5_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO5),
+	.reg = HICRA,
+	.shift = 12,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART5,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_io4_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO4),
+	.reg = HICRA,
+	.shift = 9,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART5,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_io3_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO3),
+	.reg = HICRA,
+	.shift = 6,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART5,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_io2_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO2),
+	.reg = HICRA,
+	.shift = 3,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART5,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2500_io1_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO1),
+	.reg = HICRA,
+	.shift = 0,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART5,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO6,
+		    NULL,
+		    },
+};
+
+static struct attribute *ast2500_uart_routing_attrs[] = {
+	&ast2500_io6_sel.dev_attr.attr,
+	&ast2500_uart5_sel.dev_attr.attr,
+	&ast2500_uart4_sel.dev_attr.attr,
+	&ast2500_uart3_sel.dev_attr.attr,
+	&ast2500_uart2_sel.dev_attr.attr,
+	&ast2500_uart1_sel.dev_attr.attr,
+	&ast2500_io5_sel.dev_attr.attr,
+	&ast2500_io4_sel.dev_attr.attr,
+	&ast2500_io3_sel.dev_attr.attr,
+	&ast2500_io2_sel.dev_attr.attr,
+	&ast2500_io1_sel.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ast2500_uart_routing_attr_group = {
+	.attrs = ast2500_uart_routing_attrs,
+};
+
+/* routing selector for AST26xx */
+static struct aspeed_uart_routing_selector ast2600_uart10_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART10),
+	.reg = HICR9,
+	.shift = 12,
+	.mask = 0xf,
+	.options = {
+		    UART_ROUTING_IO10,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+			UART_ROUTING_RES,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_io10_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO10),
+	.reg = HICR9,
+	.shift = 8,
+	.mask = 0xf,
+	.options = {
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+			UART_ROUTING_RES,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+			UART_ROUTING_RES,
+		    UART_ROUTING_UART10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_uart4_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART4),
+	.reg = HICRA,
+	.shift = 25,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_IO10,
+		    NULL,
+	},
+};
+
+static struct aspeed_uart_routing_selector ast2600_uart3_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART3),
+	.reg = HICRA,
+	.shift = 22,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_uart2_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART2),
+	.reg = HICRA,
+	.shift = 19,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_uart1_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_UART1),
+	.reg = HICRA,
+	.shift = 16,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_io4_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO4),
+	.reg = HICRA,
+	.shift = 9,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART10,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_io3_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO3),
+	.reg = HICRA,
+	.shift = 6,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART10,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_IO1,
+		    UART_ROUTING_IO2,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_io2_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO2),
+	.reg = HICRA,
+	.shift = 3,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART10,
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct aspeed_uart_routing_selector ast2600_io1_sel = {
+	.dev_attr = ROUTING_ATTR(UART_ROUTING_IO1),
+	.reg = HICRA,
+	.shift = 0,
+	.mask = 0x7,
+	.options = {
+		    UART_ROUTING_UART1,
+		    UART_ROUTING_UART2,
+		    UART_ROUTING_UART3,
+		    UART_ROUTING_UART4,
+		    UART_ROUTING_UART10,
+		    UART_ROUTING_IO3,
+		    UART_ROUTING_IO4,
+		    UART_ROUTING_IO10,
+		    NULL,
+		    },
+};
+
+static struct attribute *ast2600_uart_routing_attrs[] = {
+	&ast2600_uart10_sel.dev_attr.attr,
+	&ast2600_io10_sel.dev_attr.attr,
+	&ast2600_uart4_sel.dev_attr.attr,
+	&ast2600_uart3_sel.dev_attr.attr,
+	&ast2600_uart2_sel.dev_attr.attr,
+	&ast2600_uart1_sel.dev_attr.attr,
+	&ast2600_io4_sel.dev_attr.attr,
+	&ast2600_io3_sel.dev_attr.attr,
+	&ast2600_io2_sel.dev_attr.attr,
+	&ast2600_io1_sel.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ast2600_uart_routing_attr_group = {
+	.attrs = ast2600_uart_routing_attrs,
+};
+
+static ssize_t aspeed_uart_routing_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct aspeed_uart_routing *uart_routing = dev_get_drvdata(dev);
+	struct aspeed_uart_routing_selector *sel = to_routing_selector(attr);
+	int val, pos, len;
+
+	regmap_read(uart_routing->map, sel->reg, &val);
+	val = (val >> sel->shift) & sel->mask;
+
+	len = 0;
+	for (pos = 0; sel->options[pos] != NULL; ++pos) {
+		if (pos == val)
+			len += sysfs_emit_at(buf, len, "[%s] ", sel->options[pos]);
+		else
+			len += sysfs_emit_at(buf, len, "%s ", sel->options[pos]);
+	}
+
+	if (val >= pos)
+		len += sysfs_emit_at(buf, len, "[unknown(%d)]", val);
+
+	len += sysfs_emit_at(buf, len, "\n");
+
+	return len;
+}
+
+static ssize_t aspeed_uart_routing_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct aspeed_uart_routing *uart_routing = dev_get_drvdata(dev);
+	struct aspeed_uart_routing_selector *sel = to_routing_selector(attr);
+	int val;
+
+	val = __sysfs_match_string(sel->options, -1, buf);
+	if (val < 0) {
+		dev_err(dev, "invalid value \"%s\"\n", buf);
+		return -EINVAL;
+	}
+
+	regmap_update_bits(uart_routing->map, sel->reg,
+			(sel->mask << sel->shift),
+			(val & sel->mask) << sel->shift);
+
+	return count;
+}
+
+static int aspeed_uart_routing_probe(struct platform_device *pdev)
+{
+	int rc;
+	struct device *dev = &pdev->dev;
+	struct aspeed_uart_routing *uart_routing;
+
+	uart_routing = devm_kzalloc(&pdev->dev, sizeof(*uart_routing), GFP_KERNEL);
+	if (!uart_routing)
+		return -ENOMEM;
+
+	uart_routing->map = syscon_node_to_regmap(dev->parent->of_node);
+	if (IS_ERR(uart_routing->map)) {
+		dev_err(dev, "cannot get regmap\n");
+		return PTR_ERR(uart_routing->map);
+	}
+
+	uart_routing->attr_grp = of_device_get_match_data(dev);
+
+	rc = sysfs_create_group(&dev->kobj, uart_routing->attr_grp);
+	if (rc < 0)
+		return rc;
+
+	dev_set_drvdata(dev, uart_routing);
+
+	dev_info(dev, "module loaded\n");
+
+	return 0;
+}
+
+static void aspeed_uart_routing_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct aspeed_uart_routing *uart_routing = platform_get_drvdata(pdev);
+
+	sysfs_remove_group(&dev->kobj, uart_routing->attr_grp);
+}
+
+static const struct of_device_id aspeed_uart_routing_table[] = {
+	{ .compatible = "aspeed,ast2400-uart-routing",
+	  .data = &ast2500_uart_routing_attr_group },
+	{ .compatible = "aspeed,ast2500-uart-routing",
+	  .data = &ast2500_uart_routing_attr_group },
+	{ .compatible = "aspeed,ast2600-uart-routing",
+	  .data = &ast2600_uart_routing_attr_group },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, aspeed_uart_routing_table);
+
+static struct platform_driver aspeed_uart_routing_driver = {
+	.driver = {
+		.name = "aspeed-uart-routing",
+		.of_match_table = aspeed_uart_routing_table,
+	},
+	.probe = aspeed_uart_routing_probe,
+	.remove = aspeed_uart_routing_remove,
+};
+
+module_platform_driver(aspeed_uart_routing_driver);
+
+MODULE_AUTHOR("Oskar Senft <osk@google.com>");
+MODULE_AUTHOR("Chia-Wei Wang <chiawei_wang@aspeedtech.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Driver to configure Aspeed UART routing");