From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- drivers/clocksource/timer-atmel-st.c | 250 +++++++++++++++++++++++++++++++++++ 1 file changed, 250 insertions(+) create mode 100644 drivers/clocksource/timer-atmel-st.c (limited to 'drivers/clocksource/timer-atmel-st.c') diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c new file mode 100644 index 000000000..73e8aee44 --- /dev/null +++ b/drivers/clocksource/timer-atmel-st.c @@ -0,0 +1,250 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * linux/arch/arm/mach-at91/at91rm9200_time.c + * + * Copyright (C) 2003 SAN People + * Copyright (C) 2003 ATMEL + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static unsigned long last_crtr; +static u32 irqmask; +static struct clock_event_device clkevt; +static struct regmap *regmap_st; +static int timer_latch; + +/* + * The ST_CRTR is updated asynchronously to the master clock ... but + * the updates as seen by the CPU don't seem to be strictly monotonic. + * Waiting until we read the same value twice avoids glitching. + */ +static inline unsigned long read_CRTR(void) +{ + unsigned int x1, x2; + + regmap_read(regmap_st, AT91_ST_CRTR, &x1); + do { + regmap_read(regmap_st, AT91_ST_CRTR, &x2); + if (x1 == x2) + break; + x1 = x2; + } while (1); + return x1; +} + +/* + * IRQ handler for the timer. + */ +static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id) +{ + u32 sr; + + regmap_read(regmap_st, AT91_ST_SR, &sr); + sr &= irqmask; + + /* + * irqs should be disabled here, but as the irq is shared they are only + * guaranteed to be off if the timer irq is registered first. + */ + WARN_ON_ONCE(!irqs_disabled()); + + /* simulate "oneshot" timer with alarm */ + if (sr & AT91_ST_ALMS) { + clkevt.event_handler(&clkevt); + return IRQ_HANDLED; + } + + /* periodic mode should handle delayed ticks */ + if (sr & AT91_ST_PITS) { + u32 crtr = read_CRTR(); + + while (((crtr - last_crtr) & AT91_ST_CRTV) >= timer_latch) { + last_crtr += timer_latch; + clkevt.event_handler(&clkevt); + } + return IRQ_HANDLED; + } + + /* this irq is shared ... */ + return IRQ_NONE; +} + +static u64 read_clk32k(struct clocksource *cs) +{ + return read_CRTR(); +} + +static struct clocksource clk32k = { + .name = "32k_counter", + .rating = 150, + .read = read_clk32k, + .mask = CLOCKSOURCE_MASK(20), + .flags = CLOCK_SOURCE_IS_CONTINUOUS, +}; + +static void clkdev32k_disable_and_flush_irq(void) +{ + unsigned int val; + + /* Disable and flush pending timer interrupts */ + regmap_write(regmap_st, AT91_ST_IDR, AT91_ST_PITS | AT91_ST_ALMS); + regmap_read(regmap_st, AT91_ST_SR, &val); + last_crtr = read_CRTR(); +} + +static int clkevt32k_shutdown(struct clock_event_device *evt) +{ + clkdev32k_disable_and_flush_irq(); + irqmask = 0; + regmap_write(regmap_st, AT91_ST_IER, irqmask); + return 0; +} + +static int clkevt32k_set_oneshot(struct clock_event_device *dev) +{ + clkdev32k_disable_and_flush_irq(); + + /* + * ALM for oneshot irqs, set by next_event() + * before 32 seconds have passed. + */ + irqmask = AT91_ST_ALMS; + regmap_write(regmap_st, AT91_ST_RTAR, last_crtr); + regmap_write(regmap_st, AT91_ST_IER, irqmask); + return 0; +} + +static int clkevt32k_set_periodic(struct clock_event_device *dev) +{ + clkdev32k_disable_and_flush_irq(); + + /* PIT for periodic irqs; fixed rate of 1/HZ */ + irqmask = AT91_ST_PITS; + regmap_write(regmap_st, AT91_ST_PIMR, timer_latch); + regmap_write(regmap_st, AT91_ST_IER, irqmask); + return 0; +} + +static int +clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev) +{ + u32 alm; + unsigned int val; + + BUG_ON(delta < 2); + + /* The alarm IRQ uses absolute time (now+delta), not the relative + * time (delta) in our calling convention. Like all clockevents + * using such "match" hardware, we have a race to defend against. + * + * Our defense here is to have set up the clockevent device so the + * delta is at least two. That way we never end up writing RTAR + * with the value then held in CRTR ... which would mean the match + * wouldn't trigger until 32 seconds later, after CRTR wraps. + */ + alm = read_CRTR(); + + /* Cancel any pending alarm; flush any pending IRQ */ + regmap_write(regmap_st, AT91_ST_RTAR, alm); + regmap_read(regmap_st, AT91_ST_SR, &val); + + /* Schedule alarm by writing RTAR. */ + alm += delta; + regmap_write(regmap_st, AT91_ST_RTAR, alm); + + return 0; +} + +static struct clock_event_device clkevt = { + .name = "at91_tick", + .features = CLOCK_EVT_FEAT_PERIODIC | + CLOCK_EVT_FEAT_ONESHOT, + .rating = 150, + .set_next_event = clkevt32k_next_event, + .set_state_shutdown = clkevt32k_shutdown, + .set_state_periodic = clkevt32k_set_periodic, + .set_state_oneshot = clkevt32k_set_oneshot, + .tick_resume = clkevt32k_shutdown, +}; + +/* + * ST (system timer) module supports both clockevents and clocksource. + */ +static int __init atmel_st_timer_init(struct device_node *node) +{ + struct clk *sclk; + unsigned int sclk_rate, val; + int irq, ret; + + regmap_st = syscon_node_to_regmap(node); + if (IS_ERR(regmap_st)) { + pr_err("Unable to get regmap\n"); + return PTR_ERR(regmap_st); + } + + /* Disable all timer interrupts, and clear any pending ones */ + regmap_write(regmap_st, AT91_ST_IDR, + AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS); + regmap_read(regmap_st, AT91_ST_SR, &val); + + /* Get the interrupts property */ + irq = irq_of_parse_and_map(node, 0); + if (!irq) { + pr_err("Unable to get IRQ from DT\n"); + return -EINVAL; + } + + /* Make IRQs happen for the system timer */ + ret = request_irq(irq, at91rm9200_timer_interrupt, + IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL, + "at91_tick", regmap_st); + if (ret) { + pr_err("Unable to setup IRQ\n"); + return ret; + } + + sclk = of_clk_get(node, 0); + if (IS_ERR(sclk)) { + pr_err("Unable to get slow clock\n"); + return PTR_ERR(sclk); + } + + ret = clk_prepare_enable(sclk); + if (ret) { + pr_err("Could not enable slow clock\n"); + return ret; + } + + sclk_rate = clk_get_rate(sclk); + if (!sclk_rate) { + pr_err("Invalid slow clock rate\n"); + return -EINVAL; + } + timer_latch = (sclk_rate + HZ / 2) / HZ; + + /* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used + * directly for the clocksource and all clockevents, after adjusting + * its prescaler from the 1 Hz default. + */ + regmap_write(regmap_st, AT91_ST_RTMR, 1); + + /* Setup timer clockevent, with minimum of two ticks (important!!) */ + clkevt.cpumask = cpumask_of(0); + clockevents_config_and_register(&clkevt, sclk_rate, + 2, AT91_ST_ALMV); + + /* register clocksource */ + return clocksource_register_hz(&clk32k, sclk_rate); +} +TIMER_OF_DECLARE(atmel_st_timer, "atmel,at91rm9200-st", + atmel_st_timer_init); -- cgit v1.2.3