diff options
Diffstat (limited to 'arch/arm/mach-at91/at91sam926x_time.c')
| -rw-r--r-- | arch/arm/mach-at91/at91sam926x_time.c | 171 |
1 files changed, 125 insertions, 46 deletions
diff --git a/arch/arm/mach-at91/at91sam926x_time.c b/arch/arm/mach-at91/at91sam926x_time.c index e38d2377099..5cecbd7de6a 100644 --- a/arch/arm/mach-at91/at91sam926x_time.c +++ b/arch/arm/mach-at91/at91sam926x_time.c @@ -1,23 +1,20 @@ /* - * linux/arch/arm/mach-at91/at91sam926x_time.c + * at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x * * Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France * Revision 2005 M. Nicolas Diremdjian, ATMEL Rousset, France + * Converted to ClockSource/ClockEvents by David Brownell. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ - -#include <linux/init.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/kernel.h> -#include <linux/sched.h> -#include <linux/time.h> +#include <linux/clk.h> +#include <linux/clockchips.h> -#include <asm/hardware.h> -#include <asm/io.h> #include <asm/mach/time.h> #include <asm/arch/at91_pit.h> @@ -26,85 +23,167 @@ #define PIT_CPIV(x) ((x) & AT91_PIT_CPIV) #define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20) +static u32 pit_cycle; /* write-once */ +static u32 pit_cnt; /* access only w/system irq blocked */ + + /* - * Returns number of microseconds since last timer interrupt. Note that interrupts - * will have been disabled by do_gettimeofday() - * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy. + * Clocksource: just a monotonic counter of MCK/16 cycles. + * We don't care whether or not PIT irqs are enabled. */ -static unsigned long at91sam926x_gettimeoffset(void) +static cycle_t read_pit_clk(void) { - unsigned long elapsed; - unsigned long t = at91_sys_read(AT91_PIT_PIIR); + unsigned long flags; + u32 elapsed; + u32 t; + + raw_local_irq_save(flags); + elapsed = pit_cnt; + t = at91_sys_read(AT91_PIT_PIIR); + raw_local_irq_restore(flags); + + elapsed += PIT_PICNT(t) * pit_cycle; + elapsed += PIT_CPIV(t); + return elapsed; +} + +static struct clocksource pit_clk = { + .name = "pit", + .rating = 175, + .read = read_pit_clk, + .shift = 20, + .flags = CLOCK_SOURCE_IS_CONTINUOUS, +}; - elapsed = (PIT_PICNT(t) * LATCH) + PIT_CPIV(t); /* hardware clock cycles */ - return (unsigned long)(elapsed * jiffies_to_usecs(1)) / LATCH; +/* + * Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16) + */ +static void +pit_clkevt_mode(enum clock_event_mode mode, struct clock_event_device *dev) +{ + unsigned long flags; + + switch (mode) { + case CLOCK_EVT_MODE_PERIODIC: + /* update clocksource counter, then enable the IRQ */ + raw_local_irq_save(flags); + pit_cnt += pit_cycle * PIT_PICNT(at91_sys_read(AT91_PIT_PIVR)); + at91_sys_write(AT91_PIT_MR, (pit_cycle - 1) | AT91_PIT_PITEN + | AT91_PIT_PITIEN); + raw_local_irq_restore(flags); + break; + case CLOCK_EVT_MODE_ONESHOT: + BUG(); + /* FALLTHROUGH */ + case CLOCK_EVT_MODE_SHUTDOWN: + case CLOCK_EVT_MODE_UNUSED: + /* disable irq, leaving the clocksource active */ + at91_sys_write(AT91_PIT_MR, (pit_cycle - 1) | AT91_PIT_PITEN); + break; + case CLOCK_EVT_MODE_RESUME: + break; + } } +static struct clock_event_device pit_clkevt = { + .name = "pit", + .features = CLOCK_EVT_FEAT_PERIODIC, + .shift = 32, + .rating = 100, + .cpumask = CPU_MASK_CPU0, + .set_mode = pit_clkevt_mode, +}; + + /* * IRQ handler for the timer. */ -static irqreturn_t at91sam926x_timer_interrupt(int irq, void *dev_id) +static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id) { - volatile long nr_ticks; - if (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS) { /* This is a shared interrupt */ - /* Get number to ticks performed before interrupt and clear PIT interrupt */ + /* The PIT interrupt may be disabled, and is shared */ + if ((pit_clkevt.mode == CLOCK_EVT_MODE_PERIODIC) + && (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS)) { + unsigned nr_ticks; + + /* Get number of ticks performed before irq, and ack it */ nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR)); do { - timer_tick(); + pit_cnt += pit_cycle; + pit_clkevt.event_handler(&pit_clkevt); nr_ticks--; } while (nr_ticks); return IRQ_HANDLED; - } else - return IRQ_NONE; /* not handled */ + } + + return IRQ_NONE; } -static struct irqaction at91sam926x_timer_irq = { +static struct irqaction at91sam926x_pit_irq = { .name = "at91_tick", .flags = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL, - .handler = at91sam926x_timer_interrupt + .handler = at91sam926x_pit_interrupt }; -void at91sam926x_timer_reset(void) +static void at91sam926x_pit_reset(void) { - /* Disable timer */ + /* Disable timer and irqs */ at91_sys_write(AT91_PIT_MR, 0); - /* Clear any pending interrupts */ - (void) at91_sys_read(AT91_PIT_PIVR); + /* Clear any pending interrupts, wait for PIT to stop counting */ + while (PIT_CPIV(at91_sys_read(AT91_PIT_PIVR)) != 0) + cpu_relax(); - /* Set Period Interval timer and enable its interrupt */ - at91_sys_write(AT91_PIT_MR, (LATCH & AT91_PIT_PIV) | AT91_PIT_PITIEN | AT91_PIT_PITEN); + /* Start PIT but don't enable IRQ */ + at91_sys_write(AT91_PIT_MR, (pit_cycle - 1) | AT91_PIT_PITEN); } /* - * Set up timer interrupt. + * Set up both clocksource and clockevent support. */ -void __init at91sam926x_timer_init(void) +static void __init at91sam926x_pit_init(void) { - /* Initialize and enable the timer */ - at91sam926x_timer_reset(); + unsigned long pit_rate; + unsigned bits; + + /* + * Use our actual MCK to figure out how many MCK/16 ticks per + * 1/HZ period (instead of a compile-time constant LATCH). + */ + pit_rate = clk_get_rate(clk_get(NULL, "mck")) / 16; + pit_cycle = (pit_rate + HZ/2) / HZ; + WARN_ON(((pit_cycle - 1) & ~AT91_PIT_PIV) != 0); - /* Make IRQs happen for the system timer. */ - setup_irq(AT91_ID_SYS, &at91sam926x_timer_irq); + /* Initialize and enable the timer */ + at91sam926x_pit_reset(); + + /* + * Register clocksource. The high order bits of PIV are unused, + * so this isn't a 32-bit counter unless we get clockevent irqs. + */ + pit_clk.mult = clocksource_hz2mult(pit_rate, pit_clk.shift); + bits = 12 /* PICNT */ + ilog2(pit_cycle) /* PIV */; + pit_clk.mask = CLOCKSOURCE_MASK(bits); + clocksource_register(&pit_clk); + + /* Set up irq handler */ + setup_irq(AT91_ID_SYS, &at91sam926x_pit_irq); + + /* Set up and register clockevents */ + pit_clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, pit_clkevt.shift); + clockevents_register_device(&pit_clkevt); } -#ifdef CONFIG_PM -static void at91sam926x_timer_suspend(void) +static void at91sam926x_pit_suspend(void) { /* Disable timer */ at91_sys_write(AT91_PIT_MR, 0); } -#else -#define at91sam926x_timer_suspend NULL -#endif struct sys_timer at91sam926x_timer = { - .init = at91sam926x_timer_init, - .offset = at91sam926x_gettimeoffset, - .suspend = at91sam926x_timer_suspend, - .resume = at91sam926x_timer_reset, + .init = at91sam926x_pit_init, + .suspend = at91sam926x_pit_suspend, + .resume = at91sam926x_pit_reset, }; - |