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Diffstat (limited to '')
| -rw-r--r-- | drivers/clocksource/timer-atmel-pit.c | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/drivers/clocksource/timer-atmel-pit.c b/drivers/clocksource/timer-atmel-pit.c new file mode 100644 index 000000000..b4f264ed1 --- /dev/null +++ b/drivers/clocksource/timer-atmel-pit.c @@ -0,0 +1,264 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 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. + */ + +#define pr_fmt(fmt) "AT91: PIT: " fmt + +#include <linux/clk.h> +#include <linux/clockchips.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/of.h> +#include <linux/of_address.h> +#include <linux/of_irq.h> +#include <linux/slab.h> + +#define AT91_PIT_MR 0x00 /* Mode Register */ +#define AT91_PIT_PITIEN BIT(25) /* Timer Interrupt Enable */ +#define AT91_PIT_PITEN BIT(24) /* Timer Enabled */ +#define AT91_PIT_PIV GENMASK(19, 0) /* Periodic Interval Value */ + +#define AT91_PIT_SR 0x04 /* Status Register */ +#define AT91_PIT_PITS BIT(0) /* Timer Status */ + +#define AT91_PIT_PIVR 0x08 /* Periodic Interval Value Register */ +#define AT91_PIT_PIIR 0x0c /* Periodic Interval Image Register */ +#define AT91_PIT_PICNT GENMASK(31, 20) /* Interval Counter */ +#define AT91_PIT_CPIV GENMASK(19, 0) /* Inverval Value */ + +#define PIT_CPIV(x) ((x) & AT91_PIT_CPIV) +#define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20) + +struct pit_data { + struct clock_event_device clkevt; + struct clocksource clksrc; + + void __iomem *base; + u32 cycle; + u32 cnt; + unsigned int irq; + struct clk *mck; +}; + +static inline struct pit_data *clksrc_to_pit_data(struct clocksource *clksrc) +{ + return container_of(clksrc, struct pit_data, clksrc); +} + +static inline struct pit_data *clkevt_to_pit_data(struct clock_event_device *clkevt) +{ + return container_of(clkevt, struct pit_data, clkevt); +} + +static inline unsigned int pit_read(void __iomem *base, unsigned int reg_offset) +{ + return readl_relaxed(base + reg_offset); +} + +static inline void pit_write(void __iomem *base, unsigned int reg_offset, unsigned long value) +{ + writel_relaxed(value, base + reg_offset); +} + +/* + * Clocksource: just a monotonic counter of MCK/16 cycles. + * We don't care whether or not PIT irqs are enabled. + */ +static u64 read_pit_clk(struct clocksource *cs) +{ + struct pit_data *data = clksrc_to_pit_data(cs); + unsigned long flags; + u32 elapsed; + u32 t; + + raw_local_irq_save(flags); + elapsed = data->cnt; + t = pit_read(data->base, AT91_PIT_PIIR); + raw_local_irq_restore(flags); + + elapsed += PIT_PICNT(t) * data->cycle; + elapsed += PIT_CPIV(t); + return elapsed; +} + +static int pit_clkevt_shutdown(struct clock_event_device *dev) +{ + struct pit_data *data = clkevt_to_pit_data(dev); + + /* disable irq, leaving the clocksource active */ + pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN); + return 0; +} + +/* + * Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16) + */ +static int pit_clkevt_set_periodic(struct clock_event_device *dev) +{ + struct pit_data *data = clkevt_to_pit_data(dev); + + /* update clocksource counter */ + data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR)); + pit_write(data->base, AT91_PIT_MR, + (data->cycle - 1) | AT91_PIT_PITEN | AT91_PIT_PITIEN); + return 0; +} + +static void at91sam926x_pit_suspend(struct clock_event_device *cedev) +{ + struct pit_data *data = clkevt_to_pit_data(cedev); + + /* Disable timer */ + pit_write(data->base, AT91_PIT_MR, 0); +} + +static void at91sam926x_pit_reset(struct pit_data *data) +{ + /* Disable timer and irqs */ + pit_write(data->base, AT91_PIT_MR, 0); + + /* Clear any pending interrupts, wait for PIT to stop counting */ + while (PIT_CPIV(pit_read(data->base, AT91_PIT_PIVR)) != 0) + cpu_relax(); + + /* Start PIT but don't enable IRQ */ + pit_write(data->base, AT91_PIT_MR, + (data->cycle - 1) | AT91_PIT_PITEN); +} + +static void at91sam926x_pit_resume(struct clock_event_device *cedev) +{ + struct pit_data *data = clkevt_to_pit_data(cedev); + + at91sam926x_pit_reset(data); +} + +/* + * IRQ handler for the timer. + */ +static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id) +{ + struct pit_data *data = dev_id; + + /* The PIT interrupt may be disabled, and is shared */ + if (clockevent_state_periodic(&data->clkevt) && + (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) { + /* Get number of ticks performed before irq, and ack it */ + data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, + AT91_PIT_PIVR)); + data->clkevt.event_handler(&data->clkevt); + + return IRQ_HANDLED; + } + + return IRQ_NONE; +} + +/* + * Set up both clocksource and clockevent support. + */ +static int __init at91sam926x_pit_dt_init(struct device_node *node) +{ + unsigned long pit_rate; + unsigned bits; + int ret; + struct pit_data *data; + + data = kzalloc(sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + data->base = of_iomap(node, 0); + if (!data->base) { + pr_err("Could not map PIT address\n"); + ret = -ENXIO; + goto exit; + } + + data->mck = of_clk_get(node, 0); + if (IS_ERR(data->mck)) { + pr_err("Unable to get mck clk\n"); + ret = PTR_ERR(data->mck); + goto exit; + } + + ret = clk_prepare_enable(data->mck); + if (ret) { + pr_err("Unable to enable mck\n"); + goto exit; + } + + /* Get the interrupts property */ + data->irq = irq_of_parse_and_map(node, 0); + if (!data->irq) { + pr_err("Unable to get IRQ from DT\n"); + ret = -EINVAL; + goto exit; + } + + /* + * 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(data->mck) / 16; + data->cycle = DIV_ROUND_CLOSEST(pit_rate, HZ); + WARN_ON(((data->cycle - 1) & ~AT91_PIT_PIV) != 0); + + /* Initialize and enable the timer */ + at91sam926x_pit_reset(data); + + /* + * Register clocksource. The high order bits of PIV are unused, + * so this isn't a 32-bit counter unless we get clockevent irqs. + */ + bits = 12 /* PICNT */ + ilog2(data->cycle) /* PIV */; + data->clksrc.mask = CLOCKSOURCE_MASK(bits); + data->clksrc.name = "pit"; + data->clksrc.rating = 175; + data->clksrc.read = read_pit_clk; + data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS; + + ret = clocksource_register_hz(&data->clksrc, pit_rate); + if (ret) { + pr_err("Failed to register clocksource\n"); + goto exit; + } + + /* Set up irq handler */ + ret = request_irq(data->irq, at91sam926x_pit_interrupt, + IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL, + "at91_tick", data); + if (ret) { + pr_err("Unable to setup IRQ\n"); + clocksource_unregister(&data->clksrc); + goto exit; + } + + /* Set up and register clockevents */ + data->clkevt.name = "pit"; + data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC; + data->clkevt.shift = 32; + data->clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, data->clkevt.shift); + data->clkevt.rating = 100; + data->clkevt.cpumask = cpumask_of(0); + + data->clkevt.set_state_shutdown = pit_clkevt_shutdown; + data->clkevt.set_state_periodic = pit_clkevt_set_periodic; + data->clkevt.resume = at91sam926x_pit_resume; + data->clkevt.suspend = at91sam926x_pit_suspend; + clockevents_register_device(&data->clkevt); + + return 0; + +exit: + kfree(data); + return ret; +} +TIMER_OF_DECLARE(at91sam926x_pit, "atmel,at91sam9260-pit", + at91sam926x_pit_dt_init); |