// 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);
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