sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

alb_break_llc() decides whether to break LLC preference during active
load balance. It does so by testing that every runnable fair task on the
source rq prefers its LLC:

	env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable

But the two counters cover different sets. nr_pref_llc_running is updated
in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued,
so it follows queued tasks. h_nr_runnable is updated in set_delayed()/
clear_delayed() and drops delay-dequeued tasks.

So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted
in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks,
alb_break_llc() returns false, and active balance is free to pull a task
off its preferred LLC. Active balance only moves runnable tasks, and this
is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB
skips the per-task test in can_migrate_task(). The runnable set is the one
we want.

Fix it on the counter side. A task should be counted in
nr_pref_llc_running exactly while it is both queued on its preferred LLC
(pref_llc_queued) and runnable (!sched_delayed). Define that membership
once in task_pref_llc_runnable(), and adjust the counter only through
pref_llc_running_inc()/pref_llc_running_dec() from the four sites that
change either input: account_llc_enqueue(), account_llc_dequeue(),
set_delayed() and clear_delayed(). Gating every update on the same
predicate keeps the delay, wake and dequeue paths from double-counting
or underflowing; see the comments at those sites for the ordering.

nr_llc_running and sd->llc_counts are not touched and stay on queued
semantics.

Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC")
Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/
Reported-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 296 insertions, 0 deletions

diff --git a/drivers/phy/phy-google-usb.c b/drivers/phy/phy-google-usb.c
new file mode 100644
index 000000000..ab20bc20f
--- /dev/null
+++ b/drivers/phy/phy-google-usb.c
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * phy-google-usb.c - Google USB PHY driver
+ *
+ * Copyright (C) 2025, Google LLC
+ */
+
+#include <linux/bitfield.h>
+#include <linux/cleanup.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+#include <linux/usb/typec_mux.h>
+
+#define USBCS_USB2PHY_CFG19_OFFSET 0x0
+#define USBCS_USB2PHY_CFG19_PHY_CFG_PLL_FB_DIV GENMASK(19, 8)
+
+#define USBCS_USB2PHY_CFG21_OFFSET 0x8
+#define USBCS_USB2PHY_CFG21_PHY_ENABLE BIT(12)
+#define USBCS_USB2PHY_CFG21_REF_FREQ_SEL GENMASK(15, 13)
+#define USBCS_USB2PHY_CFG21_PHY_TX_DIG_BYPASS_SEL BIT(19)
+
+#define USBCS_PHY_CFG1_OFFSET 0x28
+#define USBCS_PHY_CFG1_SYS_VBUSVALID BIT(17)
+
+enum google_usb_phy_id {
+	GOOGLE_USB2_PHY,
+	GOOGLE_USB_PHY_NUM,
+};
+
+struct google_usb_phy_instance {
+	struct google_usb_phy *parent;
+	unsigned int index;
+	struct phy *phy;
+	unsigned int num_clks;
+	struct clk_bulk_data *clks;
+	unsigned int num_rsts;
+	struct reset_control_bulk_data *rsts;
+};
+
+struct google_usb_phy {
+	struct device *dev;
+	struct regmap *usb_cfg_regmap;
+	unsigned int usb2_cfg_offset;
+	void __iomem *usbdp_top_base;
+	struct google_usb_phy_instance *insts;
+	/*
+	 * Protect phy registers from concurrent access, specifically via
+	 * google_usb_set_orientation callback.
+	 */
+	struct mutex phy_mutex;
+	struct typec_switch_dev *sw;
+	enum typec_orientation orientation;
+};
+
+static void set_vbus_valid(struct google_usb_phy *gphy)
+{
+	u32 reg;
+
+	if (gphy->orientation == TYPEC_ORIENTATION_NONE) {
+		reg = readl(gphy->usbdp_top_base + USBCS_PHY_CFG1_OFFSET);
+		reg &= ~USBCS_PHY_CFG1_SYS_VBUSVALID;
+		writel(reg, gphy->usbdp_top_base + USBCS_PHY_CFG1_OFFSET);
+	} else {
+		reg = readl(gphy->usbdp_top_base + USBCS_PHY_CFG1_OFFSET);
+		reg |= USBCS_PHY_CFG1_SYS_VBUSVALID;
+		writel(reg, gphy->usbdp_top_base + USBCS_PHY_CFG1_OFFSET);
+	}
+}
+
+static int google_usb_set_orientation(struct typec_switch_dev *sw,
+				      enum typec_orientation orientation)
+{
+	struct google_usb_phy *gphy = typec_switch_get_drvdata(sw);
+
+	dev_dbg(gphy->dev, "set orientation %d\n", orientation);
+
+	gphy->orientation = orientation;
+
+	if (pm_runtime_suspended(gphy->dev))
+		return 0;
+
+	guard(mutex)(&gphy->phy_mutex);
+
+	set_vbus_valid(gphy);
+
+	return 0;
+}
+
+static int google_usb2_phy_init(struct phy *_phy)
+{
+	struct google_usb_phy_instance *inst = phy_get_drvdata(_phy);
+	struct google_usb_phy *gphy = inst->parent;
+	u32 reg;
+	int ret;
+
+	dev_dbg(gphy->dev, "initializing usb2 phy\n");
+
+	guard(mutex)(&gphy->phy_mutex);
+
+	regmap_read(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG21_OFFSET, &reg);
+	reg &= ~USBCS_USB2PHY_CFG21_PHY_TX_DIG_BYPASS_SEL;
+	reg &= ~USBCS_USB2PHY_CFG21_REF_FREQ_SEL;
+	reg |= FIELD_PREP(USBCS_USB2PHY_CFG21_REF_FREQ_SEL, 0);
+	regmap_write(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG21_OFFSET, reg);
+
+	regmap_read(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG19_OFFSET, &reg);
+	reg &= ~USBCS_USB2PHY_CFG19_PHY_CFG_PLL_FB_DIV;
+	reg |= FIELD_PREP(USBCS_USB2PHY_CFG19_PHY_CFG_PLL_FB_DIV, 368);
+	regmap_write(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG19_OFFSET, reg);
+
+	set_vbus_valid(gphy);
+
+	ret = clk_bulk_prepare_enable(inst->num_clks, inst->clks);
+	if (ret)
+		return ret;
+
+	ret = reset_control_bulk_deassert(inst->num_rsts, inst->rsts);
+	if (ret) {
+		clk_bulk_disable_unprepare(inst->num_clks, inst->clks);
+		return ret;
+	}
+
+	regmap_read(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG21_OFFSET, &reg);
+	reg |= USBCS_USB2PHY_CFG21_PHY_ENABLE;
+	regmap_write(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG21_OFFSET, reg);
+
+	return 0;
+}
+
+static int google_usb2_phy_exit(struct phy *_phy)
+{
+	struct google_usb_phy_instance *inst = phy_get_drvdata(_phy);
+	struct google_usb_phy *gphy = inst->parent;
+	u32 reg;
+
+	dev_dbg(gphy->dev, "exiting usb2 phy\n");
+
+	guard(mutex)(&gphy->phy_mutex);
+
+	regmap_read(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG21_OFFSET, &reg);
+	reg &= ~USBCS_USB2PHY_CFG21_PHY_ENABLE;
+	regmap_write(gphy->usb_cfg_regmap, gphy->usb2_cfg_offset + USBCS_USB2PHY_CFG21_OFFSET, reg);
+
+	reset_control_bulk_assert(inst->num_rsts, inst->rsts);
+	clk_bulk_disable_unprepare(inst->num_clks, inst->clks);
+
+	return 0;
+}
+
+static const struct phy_ops google_usb2_phy_ops = {
+	.init		= google_usb2_phy_init,
+	.exit		= google_usb2_phy_exit,
+};
+
+static struct phy *google_usb_phy_xlate(struct device *dev,
+					const struct of_phandle_args *args)
+{
+	struct google_usb_phy *gphy = dev_get_drvdata(dev);
+
+	if (args->args[0] >= GOOGLE_USB_PHY_NUM) {
+		dev_err(dev, "invalid PHY index requested from DT\n");
+		return ERR_PTR(-ENODEV);
+	}
+	return gphy->insts[args->args[0]].phy;
+}
+
+static int google_usb_phy_probe(struct platform_device *pdev)
+{
+	struct typec_switch_desc sw_desc = { };
+	struct google_usb_phy_instance *inst;
+	struct phy_provider *phy_provider;
+	struct device *dev = &pdev->dev;
+	struct google_usb_phy *gphy;
+	struct phy *phy;
+	u32 args[1];
+	int ret;
+
+	gphy = devm_kzalloc(dev, sizeof(*gphy), GFP_KERNEL);
+	if (!gphy)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, gphy);
+	gphy->dev = dev;
+
+	ret = devm_mutex_init(dev, &gphy->phy_mutex);
+	if (ret)
+		return ret;
+
+	gphy->usb_cfg_regmap =
+		syscon_regmap_lookup_by_phandle_args(dev->of_node,
+						     "google,usb-cfg-csr",
+						     ARRAY_SIZE(args), args);
+	if (IS_ERR(gphy->usb_cfg_regmap)) {
+		return dev_err_probe(dev, PTR_ERR(gphy->usb_cfg_regmap),
+				     "invalid usb cfg csr\n");
+	}
+
+	gphy->usb2_cfg_offset = args[0];
+
+	gphy->usbdp_top_base = devm_platform_ioremap_resource_byname(pdev,
+								     "usbdp_top");
+	if (IS_ERR(gphy->usbdp_top_base))
+		return dev_err_probe(dev, PTR_ERR(gphy->usbdp_top_base),
+				    "invalid usbdp top\n");
+
+	gphy->insts = devm_kcalloc(dev, GOOGLE_USB_PHY_NUM, sizeof(*gphy->insts), GFP_KERNEL);
+	if (!gphy->insts)
+		return -ENOMEM;
+
+	inst = &gphy->insts[GOOGLE_USB2_PHY];
+	inst->parent = gphy;
+	inst->index = GOOGLE_USB2_PHY;
+	phy = devm_phy_create(dev, NULL, &google_usb2_phy_ops);
+	if (IS_ERR(phy))
+		return dev_err_probe(dev, PTR_ERR(phy),
+				     "failed to create usb2 phy instance\n");
+	inst->phy = phy;
+	phy_set_drvdata(phy, inst);
+
+	inst->num_clks = 2;
+	inst->clks = devm_kcalloc(dev, inst->num_clks, sizeof(*inst->clks), GFP_KERNEL);
+	if (!inst->clks)
+		return -ENOMEM;
+	inst->clks[0].id = "usb2";
+	inst->clks[1].id = "usb2_apb";
+	ret = devm_clk_bulk_get(dev, inst->num_clks, inst->clks);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to get u2 phy clks\n");
+
+	inst->num_rsts = 2;
+	inst->rsts = devm_kcalloc(dev, inst->num_rsts, sizeof(*inst->rsts), GFP_KERNEL);
+	if (!inst->rsts)
+		return -ENOMEM;
+	inst->rsts[0].id = "usb2";
+	inst->rsts[1].id = "usb2_apb";
+	ret = devm_reset_control_bulk_get_exclusive(dev, inst->num_rsts, inst->rsts);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to get u2 phy resets\n");
+
+	phy_provider = devm_of_phy_provider_register(dev, google_usb_phy_xlate);
+	if (IS_ERR(phy_provider))
+		return dev_err_probe(dev, PTR_ERR(phy_provider),
+				     "failed to register phy provider\n");
+
+	pm_runtime_enable(dev);
+
+	sw_desc.fwnode = dev_fwnode(dev);
+	sw_desc.drvdata = gphy;
+	sw_desc.name = fwnode_get_name(dev_fwnode(dev));
+	sw_desc.set = google_usb_set_orientation;
+
+	gphy->sw = typec_switch_register(dev, &sw_desc);
+	if (IS_ERR(gphy->sw))
+		return dev_err_probe(dev, PTR_ERR(gphy->sw),
+				     "failed to register typec switch\n");
+
+	return 0;
+}
+
+static void google_usb_phy_remove(struct platform_device *pdev)
+{
+	struct google_usb_phy *gphy = dev_get_drvdata(&pdev->dev);
+
+	typec_switch_unregister(gphy->sw);
+	pm_runtime_disable(&pdev->dev);
+}
+
+static const struct of_device_id google_usb_phy_of_match[] = {
+	{
+		.compatible = "google,lga-usb-phy",
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, google_usb_phy_of_match);
+
+static struct platform_driver google_usb_phy = {
+	.probe	= google_usb_phy_probe,
+	.remove = google_usb_phy_remove,
+	.driver = {
+		.name		= "google-usb-phy",
+		.of_match_table	= google_usb_phy_of_match,
+	}
+};
+
+module_platform_driver(google_usb_phy);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Google USB phy driver");