/* * Copyright (C) Maxime Coquelin 2015 * Author: Maxime Coquelin <mcoquelin.stm32@gmail.com> * License terms: GNU General Public License (GPL), version 2 * * Inspired by time-efm32.c from Uwe Kleine-Koenig */ #include <linux/kernel.h> #include <linux/clocksource.h> #include <linux/clockchips.h> #include <linux/delay.h> #include <linux/irq.h> #include <linux/interrupt.h> #include <linux/of.h> #include <linux/of_address.h> #include <linux/of_irq.h> #include <linux/clk.h> #include <linux/reset.h> #include <linux/sched_clock.h> #include <linux/slab.h> #include "timer-of.h" #define TIM_CR1 0x00 #define TIM_DIER 0x0c #define TIM_SR 0x10 #define TIM_EGR 0x14 #define TIM_CNT 0x24 #define TIM_PSC 0x28 #define TIM_ARR 0x2c #define TIM_CCR1 0x34 #define TIM_CR1_CEN BIT(0) #define TIM_CR1_UDIS BIT(1) #define TIM_CR1_OPM BIT(3) #define TIM_CR1_ARPE BIT(7) #define TIM_DIER_UIE BIT(0) #define TIM_DIER_CC1IE BIT(1) #define TIM_SR_UIF BIT(0) #define TIM_EGR_UG BIT(0) #define TIM_PSC_MAX USHRT_MAX #define TIM_PSC_CLKRATE 10000 struct stm32_timer_private { int bits; }; /** * stm32_timer_of_bits_set - set accessor helper * @to: a timer_of structure pointer * @bits: the number of bits (16 or 32) * * Accessor helper to set the number of bits in the timer-of private * structure. * */ static void stm32_timer_of_bits_set(struct timer_of *to, int bits) { struct stm32_timer_private *pd = to->private_data; pd->bits = bits; } /** * stm32_timer_of_bits_get - get accessor helper * @to: a timer_of structure pointer * * Accessor helper to get the number of bits in the timer-of private * structure. * * Returns an integer corresponding to the number of bits. */ static int stm32_timer_of_bits_get(struct timer_of *to) { struct stm32_timer_private *pd = to->private_data; return pd->bits; } static void __iomem *stm32_timer_cnt __read_mostly; static u64 notrace stm32_read_sched_clock(void) { return readl_relaxed(stm32_timer_cnt); } static struct delay_timer stm32_timer_delay; static unsigned long stm32_read_delay(void) { return readl_relaxed(stm32_timer_cnt); } static void stm32_clock_event_disable(struct timer_of *to) { writel_relaxed(0, timer_of_base(to) + TIM_DIER); } /** * stm32_timer_start - Start the counter without event * @to: a timer_of structure pointer * * Start the timer in order to have the counter reset and start * incrementing but disable interrupt event when there is a counter * overflow. By default, the counter direction is used as upcounter. */ static void stm32_timer_start(struct timer_of *to) { writel_relaxed(TIM_CR1_UDIS | TIM_CR1_CEN, timer_of_base(to) + TIM_CR1); } static int stm32_clock_event_shutdown(struct clock_event_device *clkevt) { struct timer_of *to = to_timer_of(clkevt); stm32_clock_event_disable(to); return 0; } static int stm32_clock_event_set_next_event(unsigned long evt, struct clock_event_device *clkevt) { struct timer_of *to = to_timer_of(clkevt); unsigned long now, next; next = readl_relaxed(timer_of_base(to) + TIM_CNT) + evt; writel_relaxed(next, timer_of_base(to) + TIM_CCR1); now = readl_relaxed(timer_of_base(to) + TIM_CNT); if ((next - now) > evt) return -ETIME; writel_relaxed(TIM_DIER_CC1IE, timer_of_base(to) + TIM_DIER); return 0; } static int stm32_clock_event_set_periodic(struct clock_event_device *clkevt) { struct timer_of *to = to_timer_of(clkevt); stm32_timer_start(to); return stm32_clock_event_set_next_event(timer_of_period(to), clkevt); } static int stm32_clock_event_set_oneshot(struct clock_event_device *clkevt) { struct timer_of *to = to_timer_of(clkevt); stm32_timer_start(to); return 0; } static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id) { struct clock_event_device *clkevt = (struct clock_event_device *)dev_id; struct timer_of *to = to_timer_of(clkevt); writel_relaxed(0, timer_of_base(to) + TIM_SR); if (clockevent_state_periodic(clkevt)) stm32_clock_event_set_periodic(clkevt); else stm32_clock_event_shutdown(clkevt); clkevt->event_handler(clkevt); return IRQ_HANDLED; } /** * stm32_timer_width - Sort out the timer width (32/16) * @to: a pointer to a timer-of structure * * Write the 32-bit max value and read/return the result. If the timer * is 32 bits wide, the result will be UINT_MAX, otherwise it will * be truncated by the 16-bit register to USHRT_MAX. * */ static void __init stm32_timer_set_width(struct timer_of *to) { u32 width; writel_relaxed(UINT_MAX, timer_of_base(to) + TIM_ARR); width = readl_relaxed(timer_of_base(to) + TIM_ARR); stm32_timer_of_bits_set(to, width == UINT_MAX ? 32 : 16); } /** * stm32_timer_set_prescaler - Compute and set the prescaler register * @to: a pointer to a timer-of structure * * Depending on the timer width, compute the prescaler to always * target a 10MHz timer rate for 16 bits. 32-bit timers are * considered precise and long enough to not use the prescaler. */ static void __init stm32_timer_set_prescaler(struct timer_of *to) { int prescaler = 1; if (stm32_timer_of_bits_get(to) != 32) { prescaler = DIV_ROUND_CLOSEST(timer_of_rate(to), TIM_PSC_CLKRATE); /* * The prescaler register is an u16, the variable * can't be greater than TIM_PSC_MAX, let's cap it in * this case. */ prescaler = prescaler < TIM_PSC_MAX ? prescaler : TIM_PSC_MAX; } writel_relaxed(prescaler - 1, timer_of_base(to) + TIM_PSC); writel_relaxed(TIM_EGR_UG, timer_of_base(to) + TIM_EGR); writel_relaxed(0, timer_of_base(to) + TIM_SR); /* Adjust rate and period given the prescaler value */ to->of_clk.rate = DIV_ROUND_CLOSEST(to->of_clk.rate, prescaler); to->of_clk.period = DIV_ROUND_UP(to->of_clk.rate, HZ); } static int __init stm32_clocksource_init(struct timer_of *to) { u32 bits = stm32_timer_of_bits_get(to); const char *name = to->np->full_name; /* * This driver allows to register several timers and relies on * the generic time framework to select the right one. * However, nothing allows to do the same for the * sched_clock. We are not interested in a sched_clock for the * 16-bit timers but only for the 32-bit one, so if no 32-bit * timer is registered yet, we select this 32-bit timer as a * sched_clock. */ if (bits == 32 && !stm32_timer_cnt) { /* * Start immediately the counter as we will be using * it right after. */ stm32_timer_start(to); stm32_timer_cnt = timer_of_base(to) + TIM_CNT; sched_clock_register(stm32_read_sched_clock, bits, timer_of_rate(to)); pr_info("%s: STM32 sched_clock registered\n", name); stm32_timer_delay.read_current_timer = stm32_read_delay; stm32_timer_delay.freq = timer_of_rate(to); register_current_timer_delay(&stm32_timer_delay); pr_info("%s: STM32 delay timer registered\n", name); } return clocksource_mmio_init(timer_of_base(to) + TIM_CNT, name, timer_of_rate(to), bits == 32 ? 250 : 100, bits, clocksource_mmio_readl_up); } static void __init stm32_clockevent_init(struct timer_of *to) { u32 bits = stm32_timer_of_bits_get(to); to->clkevt.name = to->np->full_name; to->clkevt.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; to->clkevt.set_state_shutdown = stm32_clock_event_shutdown; to->clkevt.set_state_periodic = stm32_clock_event_set_periodic; to->clkevt.set_state_oneshot = stm32_clock_event_set_oneshot; to->clkevt.tick_resume = stm32_clock_event_shutdown; to->clkevt.set_next_event = stm32_clock_event_set_next_event; to->clkevt.rating = bits == 32 ? 250 : 100; clockevents_config_and_register(&to->clkevt, timer_of_rate(to), 0x1, (1 << bits) - 1); pr_info("%pOF: STM32 clockevent driver initialized (%d bits)\n", to->np, bits); } static int __init stm32_timer_init(struct device_node *node) { struct reset_control *rstc; struct timer_of *to; int ret; to = kzalloc(sizeof(*to), GFP_KERNEL); if (!to) return -ENOMEM; to->flags = TIMER_OF_IRQ | TIMER_OF_CLOCK | TIMER_OF_BASE; to->of_irq.handler = stm32_clock_event_handler; ret = timer_of_init(node, to); if (ret) goto err; to->private_data = kzalloc(sizeof(struct stm32_timer_private), GFP_KERNEL); if (!to->private_data) goto deinit; rstc = of_reset_control_get(node, NULL); if (!IS_ERR(rstc)) { reset_control_assert(rstc); reset_control_deassert(rstc); } stm32_timer_set_width(to); stm32_timer_set_prescaler(to); ret = stm32_clocksource_init(to); if (ret) goto deinit; stm32_clockevent_init(to); return 0; deinit: timer_of_cleanup(to); err: kfree(to); return ret; } TIMER_OF_DECLARE(stm32, "st,stm32-timer", stm32_timer_init);