sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 226 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/raspberrypi-ts.c b/drivers/input/touchscreen/raspberrypi-ts.c
new file mode 100644
index 000000000..841d39a44
--- /dev/null
+++ b/drivers/input/touchscreen/raspberrypi-ts.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Raspberry Pi firmware based touchscreen driver
+ *
+ * Copyright (C) 2015, 2017 Raspberry Pi
+ * Copyright (C) 2018 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+ */
+
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/dma-mapping.h>
+#include <linux/platform_device.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define RPI_TS_DEFAULT_WIDTH	800
+#define RPI_TS_DEFAULT_HEIGHT	480
+
+#define RPI_TS_MAX_SUPPORTED_POINTS	10
+
+#define RPI_TS_FTS_TOUCH_DOWN		0
+#define RPI_TS_FTS_TOUCH_CONTACT	2
+
+#define RPI_TS_POLL_INTERVAL		17	/* 60fps */
+
+#define RPI_TS_NPOINTS_REG_INVALIDATE	99
+
+struct rpi_ts {
+	struct platform_device *pdev;
+	struct input_dev *input;
+	struct touchscreen_properties prop;
+
+	void __iomem *fw_regs_va;
+	dma_addr_t fw_regs_phys;
+
+	int known_ids;
+};
+
+struct rpi_ts_regs {
+	u8 device_mode;
+	u8 gesture_id;
+	u8 num_points;
+	struct rpi_ts_touch {
+		u8 xh;
+		u8 xl;
+		u8 yh;
+		u8 yl;
+		u8 pressure; /* Not supported */
+		u8 area;     /* Not supported */
+	} point[RPI_TS_MAX_SUPPORTED_POINTS];
+};
+
+static void rpi_ts_poll(struct input_dev *input)
+{
+	struct rpi_ts *ts = input_get_drvdata(input);
+	struct rpi_ts_regs regs;
+	int modified_ids = 0;
+	long released_ids;
+	int event_type;
+	int touchid;
+	int x, y;
+	int i;
+
+	memcpy_fromio(&regs, ts->fw_regs_va, sizeof(regs));
+	/*
+	 * We poll the memory based register copy of the touchscreen chip using
+	 * the number of points register to know whether the copy has been
+	 * updated (we write 99 to the memory copy, the GPU will write between
+	 * 0 - 10 points)
+	 */
+	iowrite8(RPI_TS_NPOINTS_REG_INVALIDATE,
+		 ts->fw_regs_va + offsetof(struct rpi_ts_regs, num_points));
+
+	if (regs.num_points == RPI_TS_NPOINTS_REG_INVALIDATE ||
+	    (regs.num_points == 0 && ts->known_ids == 0))
+		return;
+
+	for (i = 0; i < regs.num_points; i++) {
+		x = (((int)regs.point[i].xh & 0xf) << 8) + regs.point[i].xl;
+		y = (((int)regs.point[i].yh & 0xf) << 8) + regs.point[i].yl;
+		touchid = (regs.point[i].yh >> 4) & 0xf;
+		event_type = (regs.point[i].xh >> 6) & 0x03;
+
+		modified_ids |= BIT(touchid);
+
+		if (event_type == RPI_TS_FTS_TOUCH_DOWN ||
+		    event_type == RPI_TS_FTS_TOUCH_CONTACT) {
+			input_mt_slot(input, touchid);
+			input_mt_report_slot_state(input, MT_TOOL_FINGER, 1);
+			touchscreen_report_pos(input, &ts->prop, x, y, true);
+		}
+	}
+
+	released_ids = ts->known_ids & ~modified_ids;
+	for_each_set_bit(i, &released_ids, RPI_TS_MAX_SUPPORTED_POINTS) {
+		input_mt_slot(input, i);
+		input_mt_report_slot_inactive(input);
+		modified_ids &= ~(BIT(i));
+	}
+	ts->known_ids = modified_ids;
+
+	input_mt_sync_frame(input);
+	input_sync(input);
+}
+
+static void rpi_ts_dma_cleanup(void *data)
+{
+	struct rpi_ts *ts = data;
+	struct device *dev = &ts->pdev->dev;
+
+	dma_free_coherent(dev, PAGE_SIZE, ts->fw_regs_va, ts->fw_regs_phys);
+}
+
+static int rpi_ts_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct input_dev *input;
+	struct rpi_firmware *fw;
+	struct rpi_ts *ts;
+	u32 touchbuf;
+	int error;
+
+	struct device_node *fw_node __free(device_node) = of_get_parent(np);
+	if (!fw_node) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	fw = devm_rpi_firmware_get(&pdev->dev, fw_node);
+	if (!fw)
+		return -EPROBE_DEFER;
+
+	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+	ts->pdev = pdev;
+
+	ts->fw_regs_va = dma_alloc_coherent(dev, PAGE_SIZE, &ts->fw_regs_phys,
+					    GFP_KERNEL);
+	if (!ts->fw_regs_va) {
+		dev_err(dev, "failed to dma_alloc_coherent\n");
+		return -ENOMEM;
+	}
+
+	error = devm_add_action_or_reset(dev, rpi_ts_dma_cleanup, ts);
+	if (error) {
+		dev_err(dev, "failed to devm_add_action_or_reset, %d\n", error);
+		return error;
+	}
+
+	touchbuf = (u32)ts->fw_regs_phys;
+	error = rpi_firmware_property(fw, RPI_FIRMWARE_FRAMEBUFFER_SET_TOUCHBUF,
+				      &touchbuf, sizeof(touchbuf));
+	if (error || touchbuf != 0) {
+		dev_warn(dev, "Failed to set touchbuf, %d\n", error);
+		return error;
+	}
+
+	input = devm_input_allocate_device(dev);
+	if (!input) {
+		dev_err(dev, "Failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	ts->input = input;
+	input_set_drvdata(input, ts);
+
+	input->name = "raspberrypi-ts";
+	input->id.bustype = BUS_HOST;
+
+	input_set_abs_params(input, ABS_MT_POSITION_X, 0,
+			     RPI_TS_DEFAULT_WIDTH, 0, 0);
+	input_set_abs_params(input, ABS_MT_POSITION_Y, 0,
+			     RPI_TS_DEFAULT_HEIGHT, 0, 0);
+	touchscreen_parse_properties(input, true, &ts->prop);
+
+	error = input_mt_init_slots(input, RPI_TS_MAX_SUPPORTED_POINTS,
+				    INPUT_MT_DIRECT);
+	if (error) {
+		dev_err(dev, "could not init mt slots, %d\n", error);
+		return error;
+	}
+
+	error = input_setup_polling(input, rpi_ts_poll);
+	if (error) {
+		dev_err(dev, "could not set up polling mode, %d\n", error);
+		return error;
+	}
+
+	input_set_poll_interval(input, RPI_TS_POLL_INTERVAL);
+
+	error = input_register_device(input);
+	if (error) {
+		dev_err(dev, "could not register input device, %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id rpi_ts_match[] = {
+	{ .compatible = "raspberrypi,firmware-ts", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, rpi_ts_match);
+
+static struct platform_driver rpi_ts_driver = {
+	.driver = {
+		.name = "raspberrypi-ts",
+		.of_match_table = rpi_ts_match,
+	},
+	.probe = rpi_ts_probe,
+};
+module_platform_driver(rpi_ts_driver);
+
+MODULE_AUTHOR("Gordon Hollingworth");
+MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
+MODULE_DESCRIPTION("Raspberry Pi firmware based touchscreen driver");
+MODULE_LICENSE("GPL v2");