drivers/clocksource/timer-atmel-pit.c

Source file repositories/reference/linux-study-clean/drivers/clocksource/timer-atmel-pit.c

File Facts

System
Linux kernel
Corpus path
drivers/clocksource/timer-atmel-pit.c
Extension
.c
Size
7068 bytes
Lines
265
Domain
Driver Families
Bucket
drivers/clocksource
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

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)

Annotation

Implementation Notes