From 9cc63f8bcd560c760d0b12e15bba8f81c86237cf Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 14 Aug 2026 15:43:51 -0700 Subject: Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEAD Changes: Make expedited grace periods expedite normal RCU callbacks Miscellaneous fixes: * Improve diagnostic output with character task states. * Mark accesses to inform KCSAN of concurrency design. * Move from kmalloc() to kmalloc_obj(). * Documentation updates. * Improve handling of RCU deferred quiescent states. * Clean up unused function arguments and structure fields. * Reduce show_rcu_gp_kthreads() stack space. Tasks RCU updates: * Clean up after SRCU re-implementation of Tasks Trace RCU. * Mark accesses to inform KCSAN of concurrency design. * Add ->lazy_timer status to diagnostic output. * Remove an unnecessary memory barrier. * Fix a data race, courtesy of KCSAN. * Documentation updates. * Convert cond_resched_tasks_rcu_qs() from macro to static inline function. SRCU updates: * Add Rust helpers for SRCU. * Avoid losing queued work at cleanup_srcu_struct() time. Torture-test updates: * Preparation work for immediate RCU priority deboosting. * Test RCU readers from real interrupt handlers (as opposed to softirq). * Simplify code through use of cpumask_next_wrap(). * Improve diagnostic output with character task states. * Add rcutorture.nwriters parameter to allow lightweight stall testing, and rcutorture.stall_only to make doing so easier. * Test an RCU Tasks Trace grace period implying an RCU grace period. * Make RCU Tasks Trace torturing track reader batches. * Fix a data race, courtesy of KCSAN. * Plug a shuffle_tmp_mask memory leak on kthread spawn failure. --- drivers/clocksource/timer-cs5535.c | 189 +++++++++++++++++++++++++++++++++++++ 1 file changed, 189 insertions(+) create mode 100644 drivers/clocksource/timer-cs5535.c (limited to 'drivers/clocksource/timer-cs5535.c') diff --git a/drivers/clocksource/timer-cs5535.c b/drivers/clocksource/timer-cs5535.c new file mode 100644 index 000000000..8af666c39 --- /dev/null +++ b/drivers/clocksource/timer-cs5535.c @@ -0,0 +1,189 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Clock event driver for the CS5535/CS5536 + * + * Copyright (C) 2006, Advanced Micro Devices, Inc. + * Copyright (C) 2007 Andres Salomon + * Copyright (C) 2009 Andres Salomon + * + * The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book. + */ + +#include +#include +#include +#include +#include +#include + +#define DRV_NAME "cs5535-clockevt" + +static int timer_irq; +module_param_hw_named(irq, timer_irq, int, irq, 0644); +MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT ticks."); + +/* + * We are using the 32.768kHz input clock - it's the only one that has the + * ranges we find desirable. The following table lists the suitable + * divisors and the associated Hz, minimum interval and the maximum interval: + * + * Divisor Hz Min Delta (s) Max Delta (s) + * 1 32768 .00048828125 2.000 + * 2 16384 .0009765625 4.000 + * 4 8192 .001953125 8.000 + * 8 4096 .00390625 16.000 + * 16 2048 .0078125 32.000 + * 32 1024 .015625 64.000 + * 64 512 .03125 128.000 + * 128 256 .0625 256.000 + * 256 128 .125 512.000 + */ + +static struct cs5535_mfgpt_timer *cs5535_event_clock; + +/* Selected from the table above */ + +#define MFGPT_DIVISOR 16 +#define MFGPT_SCALE 4 /* divisor = 2^(scale) */ +#define MFGPT_HZ (32768 / MFGPT_DIVISOR) +#define MFGPT_PERIODIC (MFGPT_HZ / HZ) + +/* + * The MFGPT timers on the CS5536 provide us with suitable timers to use + * as clock event sources - not as good as a HPET or APIC, but certainly + * better than the PIT. This isn't a general purpose MFGPT driver, but + * a simplified one designed specifically to act as a clock event source. + * For full details about the MFGPT, please consult the CS5536 data sheet. + */ + +static void disable_timer(struct cs5535_mfgpt_timer *timer) +{ + /* avoid races by clearing CMP1 and CMP2 unconditionally */ + cs5535_mfgpt_write(timer, MFGPT_REG_SETUP, + (uint16_t) ~MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP1 | + MFGPT_SETUP_CMP2); +} + +static void start_timer(struct cs5535_mfgpt_timer *timer, uint16_t delta) +{ + cs5535_mfgpt_write(timer, MFGPT_REG_CMP2, delta); + cs5535_mfgpt_write(timer, MFGPT_REG_COUNTER, 0); + + cs5535_mfgpt_write(timer, MFGPT_REG_SETUP, + MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2); +} + +static int mfgpt_shutdown(struct clock_event_device *evt) +{ + disable_timer(cs5535_event_clock); + return 0; +} + +static int mfgpt_set_periodic(struct clock_event_device *evt) +{ + disable_timer(cs5535_event_clock); + start_timer(cs5535_event_clock, MFGPT_PERIODIC); + return 0; +} + +static int mfgpt_next_event(unsigned long delta, struct clock_event_device *evt) +{ + start_timer(cs5535_event_clock, delta); + return 0; +} + +static struct clock_event_device cs5535_clockevent = { + .name = DRV_NAME, + .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, + .set_state_shutdown = mfgpt_shutdown, + .set_state_periodic = mfgpt_set_periodic, + .set_state_oneshot = mfgpt_shutdown, + .tick_resume = mfgpt_shutdown, + .set_next_event = mfgpt_next_event, + .rating = 250, + .owner = THIS_MODULE, +}; + +static irqreturn_t mfgpt_tick(int irq, void *dev_id) +{ + uint16_t val = cs5535_mfgpt_read(cs5535_event_clock, MFGPT_REG_SETUP); + + /* See if the interrupt was for us */ + if (!(val & (MFGPT_SETUP_SETUP | MFGPT_SETUP_CMP2 | MFGPT_SETUP_CMP1))) + return IRQ_NONE; + + /* Turn off the clock (and clear the event) */ + disable_timer(cs5535_event_clock); + + if (clockevent_state_detached(&cs5535_clockevent) || + clockevent_state_shutdown(&cs5535_clockevent)) + return IRQ_HANDLED; + + /* Clear the counter */ + cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_COUNTER, 0); + + /* Restart the clock in periodic mode */ + + if (clockevent_state_periodic(&cs5535_clockevent)) + cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP, + MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2); + + cs5535_clockevent.event_handler(&cs5535_clockevent); + return IRQ_HANDLED; +} + +static int __init cs5535_mfgpt_init(void) +{ + unsigned long flags = IRQF_NOBALANCING | IRQF_TIMER | IRQF_SHARED; + struct cs5535_mfgpt_timer *timer; + int ret; + uint16_t val; + + timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING); + if (!timer) { + printk(KERN_ERR DRV_NAME ": Could not allocate MFGPT timer\n"); + return -ENODEV; + } + cs5535_event_clock = timer; + + /* Set up the IRQ on the MFGPT side */ + if (cs5535_mfgpt_setup_irq(timer, MFGPT_CMP2, &timer_irq)) { + printk(KERN_ERR DRV_NAME ": Could not set up IRQ %d\n", + timer_irq); + goto err_timer; + } + + /* And register it with the kernel */ + ret = request_irq(timer_irq, mfgpt_tick, flags, DRV_NAME, timer); + if (ret) { + printk(KERN_ERR DRV_NAME ": Unable to set up the interrupt.\n"); + goto err_irq; + } + + /* Set the clock scale and enable the event mode for CMP2 */ + val = MFGPT_SCALE | (3 << 8); + + cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP, val); + + /* Set up the clock event */ + printk(KERN_INFO DRV_NAME + ": Registering MFGPT timer as a clock event, using IRQ %d\n", + timer_irq); + clockevents_config_and_register(&cs5535_clockevent, MFGPT_HZ, + 0xF, 0xFFFE); + + return 0; + +err_irq: + cs5535_mfgpt_release_irq(cs5535_event_clock, MFGPT_CMP2, &timer_irq); +err_timer: + cs5535_mfgpt_free_timer(cs5535_event_clock); + printk(KERN_ERR DRV_NAME ": Unable to set up the MFGPT clock source\n"); + return -EIO; +} + +module_init(cs5535_mfgpt_init); + +MODULE_AUTHOR("Andres Salomon "); +MODULE_DESCRIPTION("CS5535/CS5536 MFGPT clock event driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1