arch/nios2/kernel/time.c

Source file repositories/reference/linux-study-clean/arch/nios2/kernel/time.c

File Facts

System
Linux kernel
Corpus path
arch/nios2/kernel/time.c
Extension
.c
Size
8569 bytes
Lines
360
Domain
Architecture Layer
Bucket
arch/nios2
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct nios2_timer {
	void __iomem *base;
	unsigned long freq;
};

struct nios2_clockevent_dev {
	struct nios2_timer timer;
	struct clock_event_device ced;
};

struct nios2_clocksource {
	struct nios2_timer timer;
	struct clocksource cs;
};

static inline struct nios2_clockevent_dev *
	to_nios2_clkevent(struct clock_event_device *evt)
{
	return container_of(evt, struct nios2_clockevent_dev, ced);
}

static inline struct nios2_clocksource *
	to_nios2_clksource(struct clocksource *cs)
{
	return container_of(cs, struct nios2_clocksource, cs);
}

static u16 timer_readw(struct nios2_timer *timer, u32 offs)
{
	return readw(timer->base + offs);
}

static void timer_writew(struct nios2_timer *timer, u16 val, u32 offs)
{
	writew(val, timer->base + offs);
}

static inline unsigned long read_timersnapshot(struct nios2_timer *timer)
{
	unsigned long count;

	timer_writew(timer, 0, ALTERA_TIMER_SNAPL_REG);
	count = timer_readw(timer, ALTERA_TIMER_SNAPH_REG) << 16 |
		timer_readw(timer, ALTERA_TIMER_SNAPL_REG);

	return count;
}

static u64 nios2_timer_read(struct clocksource *cs)
{
	struct nios2_clocksource *nios2_cs = to_nios2_clksource(cs);
	unsigned long flags;
	u32 count;

	local_irq_save(flags);
	count = read_timersnapshot(&nios2_cs->timer);
	local_irq_restore(flags);

	/* Counter is counting down */
	return ~count;
}

static struct nios2_clocksource nios2_cs = {
	.cs = {
		.name	= "nios2-clksrc",
		.rating	= 250,
		.read	= nios2_timer_read,
		.mask	= CLOCKSOURCE_MASK(32),
		.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
	},
};

cycles_t get_cycles(void)
{
	/* Only read timer if it has been initialized */
	if (nios2_cs.timer.base)
		return nios2_timer_read(&nios2_cs.cs);
	return 0;
}
EXPORT_SYMBOL(get_cycles);

static void nios2_timer_start(struct nios2_timer *timer)
{
	u16 ctrl;

	ctrl = timer_readw(timer, ALTERA_TIMER_CONTROL_REG);
	ctrl |= ALTERA_TIMER_CONTROL_START_MSK;
	timer_writew(timer, ctrl, ALTERA_TIMER_CONTROL_REG);
}

Annotation

Implementation Notes