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, 228 insertions, 0 deletions

diff --git a/drivers/nvmem/lan9662-otpc.c b/drivers/nvmem/lan9662-otpc.c
new file mode 100644
index 000000000..62d1d6381
--- /dev/null
+++ b/drivers/nvmem/lan9662-otpc.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define OTP_OTP_PWR_DN(t)			(t + 0x00)
+#define OTP_OTP_PWR_DN_OTP_PWRDN_N		BIT(0)
+#define OTP_OTP_ADDR_HI(t)			(t + 0x04)
+#define OTP_OTP_ADDR_LO(t)			(t + 0x08)
+#define OTP_OTP_PRGM_DATA(t)			(t + 0x10)
+#define OTP_OTP_PRGM_MODE(t)			(t + 0x14)
+#define OTP_OTP_PRGM_MODE_OTP_PGM_MODE_BYTE	BIT(0)
+#define OTP_OTP_RD_DATA(t)			(t + 0x18)
+#define OTP_OTP_FUNC_CMD(t)			(t + 0x20)
+#define OTP_OTP_FUNC_CMD_OTP_PROGRAM		BIT(1)
+#define OTP_OTP_FUNC_CMD_OTP_READ		BIT(0)
+#define OTP_OTP_CMD_GO(t)			(t + 0x28)
+#define OTP_OTP_CMD_GO_OTP_GO			BIT(0)
+#define OTP_OTP_PASS_FAIL(t)			(t + 0x2c)
+#define OTP_OTP_PASS_FAIL_OTP_READ_PROHIBITED	BIT(3)
+#define OTP_OTP_PASS_FAIL_OTP_WRITE_PROHIBITED	BIT(2)
+#define OTP_OTP_PASS_FAIL_OTP_FAIL		BIT(0)
+#define OTP_OTP_STATUS(t)			(t + 0x30)
+#define OTP_OTP_STATUS_OTP_CPUMPEN		BIT(1)
+#define OTP_OTP_STATUS_OTP_BUSY			BIT(0)
+
+#define OTP_SLEEP_US 10
+#define OTP_TIMEOUT_US 500000
+
+struct lan9662_otp {
+	struct device *dev;
+	void __iomem *base;
+};
+
+static int lan9662_otp_wait_flag_clear(void __iomem *reg, u32 flag)
+{
+	u32 val;
+
+	return readl_poll_timeout(reg, val, !(val & flag),
+				  OTP_SLEEP_US, OTP_TIMEOUT_US);
+}
+
+static int lan9662_otp_power(struct lan9662_otp *otp, bool up)
+{
+	void __iomem *pwrdn = OTP_OTP_PWR_DN(otp->base);
+
+	if (up) {
+		writel(readl(pwrdn) & ~OTP_OTP_PWR_DN_OTP_PWRDN_N, pwrdn);
+		if (lan9662_otp_wait_flag_clear(OTP_OTP_STATUS(otp->base),
+						OTP_OTP_STATUS_OTP_CPUMPEN))
+			return -ETIMEDOUT;
+	} else {
+		writel(readl(pwrdn) | OTP_OTP_PWR_DN_OTP_PWRDN_N, pwrdn);
+	}
+
+	return 0;
+}
+
+static int lan9662_otp_execute(struct lan9662_otp *otp)
+{
+	if (lan9662_otp_wait_flag_clear(OTP_OTP_CMD_GO(otp->base),
+					OTP_OTP_CMD_GO_OTP_GO))
+		return -ETIMEDOUT;
+
+	if (lan9662_otp_wait_flag_clear(OTP_OTP_STATUS(otp->base),
+					OTP_OTP_STATUS_OTP_BUSY))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static void lan9662_otp_set_address(struct lan9662_otp *otp, u32 offset)
+{
+	writel(0xff & (offset >> 8), OTP_OTP_ADDR_HI(otp->base));
+	writel(0xff & offset, OTP_OTP_ADDR_LO(otp->base));
+}
+
+static int lan9662_otp_read_byte(struct lan9662_otp *otp, u32 offset, u8 *dst)
+{
+	u32 pass;
+	int rc;
+
+	lan9662_otp_set_address(otp, offset);
+	writel(OTP_OTP_FUNC_CMD_OTP_READ, OTP_OTP_FUNC_CMD(otp->base));
+	writel(OTP_OTP_CMD_GO_OTP_GO, OTP_OTP_CMD_GO(otp->base));
+	rc = lan9662_otp_execute(otp);
+	if (!rc) {
+		pass = readl(OTP_OTP_PASS_FAIL(otp->base));
+		if (pass & OTP_OTP_PASS_FAIL_OTP_READ_PROHIBITED)
+			return -EACCES;
+		*dst = (u8) readl(OTP_OTP_RD_DATA(otp->base));
+	}
+	return rc;
+}
+
+static int lan9662_otp_write_byte(struct lan9662_otp *otp, u32 offset, u8 data)
+{
+	u32 pass;
+	int rc;
+
+	lan9662_otp_set_address(otp, offset);
+	writel(OTP_OTP_PRGM_MODE_OTP_PGM_MODE_BYTE, OTP_OTP_PRGM_MODE(otp->base));
+	writel(data, OTP_OTP_PRGM_DATA(otp->base));
+	writel(OTP_OTP_FUNC_CMD_OTP_PROGRAM, OTP_OTP_FUNC_CMD(otp->base));
+	writel(OTP_OTP_CMD_GO_OTP_GO, OTP_OTP_CMD_GO(otp->base));
+
+	rc = lan9662_otp_execute(otp);
+	if (!rc) {
+		pass = readl(OTP_OTP_PASS_FAIL(otp->base));
+		if (pass & OTP_OTP_PASS_FAIL_OTP_WRITE_PROHIBITED)
+			return -EACCES;
+		if (pass & OTP_OTP_PASS_FAIL_OTP_FAIL)
+			return -EIO;
+	}
+	return rc;
+}
+
+static int lan9662_otp_read(void *context, unsigned int offset,
+			    void *_val, size_t bytes)
+{
+	struct lan9662_otp *otp = context;
+	u8 *val = _val;
+	uint8_t data;
+	int i, rc = 0;
+
+	lan9662_otp_power(otp, true);
+	for (i = 0; i < bytes; i++) {
+		rc = lan9662_otp_read_byte(otp, offset + i, &data);
+		if (rc < 0)
+			break;
+		*val++ = data;
+	}
+	lan9662_otp_power(otp, false);
+
+	return rc;
+}
+
+static int lan9662_otp_write(void *context, unsigned int offset,
+			     void *_val, size_t bytes)
+{
+	struct lan9662_otp *otp = context;
+	u8 *val = _val;
+	u8 data, newdata;
+	int i, rc = 0;
+
+	lan9662_otp_power(otp, true);
+	for (i = 0; i < bytes; i++) {
+		/* Skip zero bytes */
+		if (val[i]) {
+			rc = lan9662_otp_read_byte(otp, offset + i, &data);
+			if (rc < 0)
+				break;
+
+			newdata = data | val[i];
+			if (newdata == data)
+				continue;
+
+			rc = lan9662_otp_write_byte(otp, offset + i,
+						      newdata);
+			if (rc < 0)
+				break;
+		}
+	}
+	lan9662_otp_power(otp, false);
+
+	return rc;
+}
+
+static struct nvmem_config otp_config = {
+	.name = "lan9662-otp",
+	.stride = 1,
+	.word_size = 1,
+	.reg_read = lan9662_otp_read,
+	.reg_write = lan9662_otp_write,
+};
+
+static int lan9662_otp_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct nvmem_device *nvmem;
+	struct lan9662_otp *otp;
+
+	otp = devm_kzalloc(&pdev->dev, sizeof(*otp), GFP_KERNEL);
+	if (!otp)
+		return -ENOMEM;
+
+	otp->dev = dev;
+	otp->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(otp->base))
+		return PTR_ERR(otp->base);
+
+	otp_config.priv = otp;
+	otp_config.dev = dev;
+	otp_config.size = (uintptr_t) device_get_match_data(dev);
+
+	nvmem = devm_nvmem_register(dev, &otp_config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id lan9662_otp_match[] = {
+	{
+		.compatible = "microchip,lan9662-otpc",
+		.data = (const void *) SZ_8K,
+	},
+	{
+		.compatible = "microchip,lan9691-otpc",
+		.data = (const void *) SZ_16K,
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, lan9662_otp_match);
+
+static struct platform_driver lan9662_otp_driver = {
+	.probe = lan9662_otp_probe,
+	.driver = {
+		.name = "lan9662-otp",
+		.of_match_table = lan9662_otp_match,
+	},
+};
+module_platform_driver(lan9662_otp_driver);
+
+MODULE_AUTHOR("Horatiu Vultur <horatiu.vultur@microchip.com>");
+MODULE_DESCRIPTION("lan9662 OTP driver");
+MODULE_LICENSE("GPL");