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>

2 files changed, 241 insertions, 0 deletions

diff --git a/drivers/clk/axis/Makefile b/drivers/clk/axis/Makefile
new file mode 100644
index 000000000..a6a9bbe7f
--- /dev/null
+++ b/drivers/clk/axis/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_MACH_ARTPEC6)	+= clk-artpec6.o
diff --git a/drivers/clk/axis/clk-artpec6.c b/drivers/clk/axis/clk-artpec6.c
new file mode 100644
index 000000000..a6f149962
--- /dev/null
+++ b/drivers/clk/axis/clk-artpec6.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ARTPEC-6 clock initialization
+ *
+ * Copyright 2015-2016 Axis Communications AB.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <dt-bindings/clock/axis,artpec6-clkctrl.h>
+
+#define NUM_I2S_CLOCKS 2
+
+struct artpec6_clkctrl_drvdata {
+	struct clk *clk_table[ARTPEC6_CLK_NUMCLOCKS];
+	void __iomem *syscon_base;
+	struct clk_onecell_data clk_data;
+	spinlock_t i2scfg_lock;
+};
+
+static struct artpec6_clkctrl_drvdata *clkdata;
+
+static const char *const i2s_clk_names[NUM_I2S_CLOCKS] = {
+	"i2s0",
+	"i2s1",
+};
+
+static const int i2s_clk_indexes[NUM_I2S_CLOCKS] = {
+	ARTPEC6_CLK_I2S0_CLK,
+	ARTPEC6_CLK_I2S1_CLK,
+};
+
+static void of_artpec6_clkctrl_setup(struct device_node *np)
+{
+	int i;
+	const char *sys_refclk_name;
+	u32 pll_mode, pll_m, pll_n;
+	struct clk **clks;
+
+	/* Mandatory parent clock. */
+	i = of_property_match_string(np, "clock-names", "sys_refclk");
+	if (i < 0)
+		return;
+
+	sys_refclk_name = of_clk_get_parent_name(np, i);
+
+	clkdata = kzalloc_obj(*clkdata);
+	if (!clkdata)
+		return;
+
+	clks = clkdata->clk_table;
+
+	for (i = 0; i < ARTPEC6_CLK_NUMCLOCKS; ++i)
+		clks[i] = ERR_PTR(-EPROBE_DEFER);
+
+	clkdata->syscon_base = of_iomap(np, 0);
+	BUG_ON(clkdata->syscon_base == NULL);
+
+	/* Read PLL1 factors configured by boot strap pins. */
+	pll_mode = (readl(clkdata->syscon_base) >> 6) & 3;
+	switch (pll_mode) {
+	case 0:		/* DDR3-2133 mode */
+		pll_m = 4;
+		pll_n = 85;
+		break;
+	case 1:		/* DDR3-1866 mode */
+		pll_m = 6;
+		pll_n = 112;
+		break;
+	case 2:		/* DDR3-1600 mode */
+		pll_m = 4;
+		pll_n = 64;
+		break;
+	case 3:		/* DDR3-1333 mode */
+		pll_m = 8;
+		pll_n = 106;
+		break;
+	}
+
+	clks[ARTPEC6_CLK_CPU] =
+	    clk_register_fixed_factor(NULL, "cpu", sys_refclk_name, 0, pll_n,
+				      pll_m);
+	clks[ARTPEC6_CLK_CPU_PERIPH] =
+	    clk_register_fixed_factor(NULL, "cpu_periph", "cpu", 0, 1, 2);
+
+	/* EPROBE_DEFER on the apb_clock is not handled in amba devices. */
+	clks[ARTPEC6_CLK_UART_PCLK] =
+	    clk_register_fixed_factor(NULL, "uart_pclk", "cpu", 0, 1, 8);
+	clks[ARTPEC6_CLK_UART_REFCLK] =
+	    clk_register_fixed_rate(NULL, "uart_ref", sys_refclk_name, 0,
+				    50000000);
+
+	clks[ARTPEC6_CLK_SPI_PCLK] =
+	    clk_register_fixed_factor(NULL, "spi_pclk", "cpu", 0, 1, 8);
+	clks[ARTPEC6_CLK_SPI_SSPCLK] =
+	    clk_register_fixed_rate(NULL, "spi_sspclk", sys_refclk_name, 0,
+				    50000000);
+
+	clks[ARTPEC6_CLK_DBG_PCLK] =
+	    clk_register_fixed_factor(NULL, "dbg_pclk", "cpu", 0, 1, 8);
+
+	clkdata->clk_data.clks = clkdata->clk_table;
+	clkdata->clk_data.clk_num = ARTPEC6_CLK_NUMCLOCKS;
+
+	of_clk_add_provider(np, of_clk_src_onecell_get, &clkdata->clk_data);
+}
+
+CLK_OF_DECLARE_DRIVER(artpec6_clkctrl, "axis,artpec6-clkctrl",
+		      of_artpec6_clkctrl_setup);
+
+static int artpec6_clkctrl_probe(struct platform_device *pdev)
+{
+	int propidx;
+	struct device_node *np = pdev->dev.of_node;
+	struct device *dev = &pdev->dev;
+	struct clk **clks = clkdata->clk_table;
+	const char *sys_refclk_name;
+	const char *i2s_refclk_name = NULL;
+	const char *frac_clk_name[2] = { NULL, NULL };
+	const char *i2s_mux_parents[2];
+	u32 muxreg;
+	int i;
+	int err = 0;
+
+	/* Mandatory parent clock. */
+	propidx = of_property_match_string(np, "clock-names", "sys_refclk");
+	if (propidx < 0)
+		return -EINVAL;
+
+	sys_refclk_name = of_clk_get_parent_name(np, propidx);
+
+	/* Find clock names of optional parent clocks. */
+	propidx = of_property_match_string(np, "clock-names", "i2s_refclk");
+	if (propidx >= 0)
+		i2s_refclk_name = of_clk_get_parent_name(np, propidx);
+
+	propidx = of_property_match_string(np, "clock-names", "frac_clk0");
+	if (propidx >= 0)
+		frac_clk_name[0] = of_clk_get_parent_name(np, propidx);
+	propidx = of_property_match_string(np, "clock-names", "frac_clk1");
+	if (propidx >= 0)
+		frac_clk_name[1] = of_clk_get_parent_name(np, propidx);
+
+	spin_lock_init(&clkdata->i2scfg_lock);
+
+	clks[ARTPEC6_CLK_NAND_CLKA] =
+	    clk_register_fixed_factor(dev, "nand_clka", "cpu", 0, 1, 8);
+	clks[ARTPEC6_CLK_NAND_CLKB] =
+	    clk_register_fixed_rate(dev, "nand_clkb", sys_refclk_name, 0,
+				    100000000);
+	clks[ARTPEC6_CLK_ETH_ACLK] =
+	    clk_register_fixed_factor(dev, "eth_aclk", "cpu", 0, 1, 4);
+	clks[ARTPEC6_CLK_DMA_ACLK] =
+	    clk_register_fixed_factor(dev, "dma_aclk", "cpu", 0, 1, 4);
+	clks[ARTPEC6_CLK_PTP_REF] =
+	    clk_register_fixed_rate(dev, "ptp_ref", sys_refclk_name, 0,
+				    100000000);
+	clks[ARTPEC6_CLK_SD_PCLK] =
+	    clk_register_fixed_rate(dev, "sd_pclk", sys_refclk_name, 0,
+				    100000000);
+	clks[ARTPEC6_CLK_SD_IMCLK] =
+	    clk_register_fixed_rate(dev, "sd_imclk", sys_refclk_name, 0,
+				    100000000);
+	clks[ARTPEC6_CLK_I2S_HST] =
+	    clk_register_fixed_factor(dev, "i2s_hst", "cpu", 0, 1, 8);
+
+	for (i = 0; i < NUM_I2S_CLOCKS; ++i) {
+		if (i2s_refclk_name && frac_clk_name[i]) {
+			i2s_mux_parents[0] = frac_clk_name[i];
+			i2s_mux_parents[1] = i2s_refclk_name;
+
+			clks[i2s_clk_indexes[i]] =
+			    clk_register_mux(dev, i2s_clk_names[i],
+					     i2s_mux_parents, 2,
+					     CLK_SET_RATE_NO_REPARENT |
+					     CLK_SET_RATE_PARENT,
+					     clkdata->syscon_base + 0x14, i, 1,
+					     0, &clkdata->i2scfg_lock);
+		} else if (frac_clk_name[i]) {
+			/* Lock the mux for internal clock reference. */
+			muxreg = readl(clkdata->syscon_base + 0x14);
+			muxreg &= ~BIT(i);
+			writel(muxreg, clkdata->syscon_base + 0x14);
+			clks[i2s_clk_indexes[i]] =
+			    clk_register_fixed_factor(dev, i2s_clk_names[i],
+						      frac_clk_name[i], 0, 1,
+						      1);
+		} else if (i2s_refclk_name) {
+			/* Lock the mux for external clock reference. */
+			muxreg = readl(clkdata->syscon_base + 0x14);
+			muxreg |= BIT(i);
+			writel(muxreg, clkdata->syscon_base + 0x14);
+			clks[i2s_clk_indexes[i]] =
+			    clk_register_fixed_factor(dev, i2s_clk_names[i],
+						      i2s_refclk_name, 0, 1, 1);
+		}
+	}
+
+	clks[ARTPEC6_CLK_I2C] =
+	    clk_register_fixed_rate(dev, "i2c", sys_refclk_name, 0, 100000000);
+
+	clks[ARTPEC6_CLK_SYS_TIMER] =
+	    clk_register_fixed_rate(dev, "timer", sys_refclk_name, 0,
+				    100000000);
+	clks[ARTPEC6_CLK_FRACDIV_IN] =
+	    clk_register_fixed_rate(dev, "fracdiv_in", sys_refclk_name, 0,
+				    600000000);
+
+	for (i = 0; i < ARTPEC6_CLK_NUMCLOCKS; ++i) {
+		if (IS_ERR(clks[i]) && PTR_ERR(clks[i]) != -EPROBE_DEFER) {
+			dev_err(dev,
+				"Failed to register clock at index %d err=%ld\n",
+				i, PTR_ERR(clks[i]));
+			err = PTR_ERR(clks[i]);
+		}
+	}
+
+	return err;
+}
+
+static const struct of_device_id artpec_clkctrl_of_match[] = {
+	{ .compatible = "axis,artpec6-clkctrl" },
+	{}
+};
+
+static struct platform_driver artpec6_clkctrl_driver = {
+	.probe = artpec6_clkctrl_probe,
+	.driver = {
+		   .name = "artpec6_clkctrl",
+		   .of_match_table = artpec_clkctrl_of_match,
+	},
+};
+
+builtin_platform_driver(artpec6_clkctrl_driver);