From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug 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 Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- drivers/rtc/rtc-ds2404.c | 225 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 225 insertions(+) create mode 100644 drivers/rtc/rtc-ds2404.c (limited to 'drivers/rtc/rtc-ds2404.c') diff --git a/drivers/rtc/rtc-ds2404.c b/drivers/rtc/rtc-ds2404.c new file mode 100644 index 000000000..217694eca --- /dev/null +++ b/drivers/rtc/rtc-ds2404.c @@ -0,0 +1,225 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2012 Sven Schnelle + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#define DS2404_STATUS_REG 0x200 +#define DS2404_CONTROL_REG 0x201 +#define DS2404_RTC_REG 0x202 + +#define DS2404_WRITE_SCRATCHPAD_CMD 0x0f +#define DS2404_READ_SCRATCHPAD_CMD 0xaa +#define DS2404_COPY_SCRATCHPAD_CMD 0x55 +#define DS2404_READ_MEMORY_CMD 0xf0 + +#define DS2404_RST 0 +#define DS2404_CLK 1 +#define DS2404_DQ 2 + +struct ds2404 { + struct device *dev; + struct gpio_desc *rst_gpiod; + struct gpio_desc *clk_gpiod; + struct gpio_desc *dq_gpiod; +}; + +static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + + /* This will de-assert RESET, declare this GPIO as GPIOD_ACTIVE_LOW */ + chip->rst_gpiod = devm_gpiod_get(dev, "rst", GPIOD_OUT_LOW); + if (IS_ERR(chip->rst_gpiod)) + return PTR_ERR(chip->rst_gpiod); + + chip->clk_gpiod = devm_gpiod_get(dev, "clk", GPIOD_OUT_HIGH); + if (IS_ERR(chip->clk_gpiod)) + return PTR_ERR(chip->clk_gpiod); + + chip->dq_gpiod = devm_gpiod_get(dev, "dq", GPIOD_ASIS); + if (IS_ERR(chip->dq_gpiod)) + return PTR_ERR(chip->dq_gpiod); + + return 0; +} + +static void ds2404_reset(struct ds2404 *chip) +{ + gpiod_set_value(chip->rst_gpiod, 1); + udelay(1000); + gpiod_set_value(chip->rst_gpiod, 0); + gpiod_set_value(chip->clk_gpiod, 0); + gpiod_direction_output(chip->dq_gpiod, 0); + udelay(10); +} + +static void ds2404_write_byte(struct ds2404 *chip, u8 byte) +{ + int i; + + gpiod_direction_output(chip->dq_gpiod, 1); + for (i = 0; i < 8; i++) { + gpiod_set_value(chip->dq_gpiod, byte & (1 << i)); + udelay(10); + gpiod_set_value(chip->clk_gpiod, 1); + udelay(10); + gpiod_set_value(chip->clk_gpiod, 0); + udelay(10); + } +} + +static u8 ds2404_read_byte(struct ds2404 *chip) +{ + int i; + u8 ret = 0; + + gpiod_direction_input(chip->dq_gpiod); + + for (i = 0; i < 8; i++) { + gpiod_set_value(chip->clk_gpiod, 0); + udelay(10); + if (gpiod_get_value(chip->dq_gpiod)) + ret |= 1 << i; + gpiod_set_value(chip->clk_gpiod, 1); + udelay(10); + } + return ret; +} + +static void ds2404_read_memory(struct ds2404 *chip, u16 offset, + int length, u8 *out) +{ + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_READ_MEMORY_CMD); + ds2404_write_byte(chip, offset & 0xff); + ds2404_write_byte(chip, (offset >> 8) & 0xff); + while (length--) + *out++ = ds2404_read_byte(chip); +} + +static void ds2404_write_memory(struct ds2404 *chip, u16 offset, + int length, u8 *out) +{ + int i; + u8 ta01, ta02, es; + + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_WRITE_SCRATCHPAD_CMD); + ds2404_write_byte(chip, offset & 0xff); + ds2404_write_byte(chip, (offset >> 8) & 0xff); + + for (i = 0; i < length; i++) + ds2404_write_byte(chip, out[i]); + + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_READ_SCRATCHPAD_CMD); + + ta01 = ds2404_read_byte(chip); + ta02 = ds2404_read_byte(chip); + es = ds2404_read_byte(chip); + + for (i = 0; i < length; i++) { + if (out[i] != ds2404_read_byte(chip)) { + dev_err(chip->dev, "read invalid data\n"); + return; + } + } + + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_COPY_SCRATCHPAD_CMD); + ds2404_write_byte(chip, ta01); + ds2404_write_byte(chip, ta02); + ds2404_write_byte(chip, es); + + while (gpiod_get_value(chip->dq_gpiod)) + ; +} + +static void ds2404_enable_osc(struct ds2404 *chip) +{ + u8 in[1] = { 0x10 }; /* enable oscillator */ + + ds2404_write_memory(chip, 0x201, 1, in); +} + +static int ds2404_read_time(struct device *dev, struct rtc_time *dt) +{ + struct ds2404 *chip = dev_get_drvdata(dev); + unsigned long time = 0; + __le32 hw_time = 0; + + ds2404_read_memory(chip, 0x203, 4, (u8 *)&hw_time); + time = le32_to_cpu(hw_time); + + rtc_time64_to_tm(time, dt); + return 0; +} + +static int ds2404_set_time(struct device *dev, struct rtc_time *dt) +{ + struct ds2404 *chip = dev_get_drvdata(dev); + u32 time = cpu_to_le32(rtc_tm_to_time64(dt)); + ds2404_write_memory(chip, 0x203, 4, (u8 *)&time); + return 0; +} + +static const struct rtc_class_ops ds2404_rtc_ops = { + .read_time = ds2404_read_time, + .set_time = ds2404_set_time, +}; + +static int rtc_probe(struct platform_device *pdev) +{ + struct ds2404 *chip; + struct rtc_device *rtc; + int retval = -EBUSY; + + chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL); + if (!chip) + return -ENOMEM; + + chip->dev = &pdev->dev; + + rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + retval = ds2404_gpio_map(chip, pdev); + if (retval) + return retval; + + platform_set_drvdata(pdev, chip); + + rtc->ops = &ds2404_rtc_ops; + rtc->range_max = U32_MAX; + + retval = devm_rtc_register_device(rtc); + if (retval) + return retval; + + ds2404_enable_osc(chip); + return 0; +} + +static struct platform_driver rtc_device_driver = { + .probe = rtc_probe, + .driver = { + .name = "ds2404", + }, +}; +module_platform_driver(rtc_device_driver); + +MODULE_DESCRIPTION("DS2404 RTC"); +MODULE_AUTHOR("Sven Schnelle"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ds2404"); -- cgit v1.3.1