UM0851 datasheet(30/245 Pages) STMICROELECTRONICS

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Platform section

UM0851

30/245

Doc ID 16604 Rev 2

static struct spear_timer *gpt;

u32 tick_rate;

gpt = spear_timer_request_specific(2);

BUG_ON(gpt == NULL);

spear_timer_set_source(gpt, SPEAR_TIMER_SRC_SYS_CLK);

/* initialize other fields ot clocksource structure */

...

/* load the counter, start timer */

spear_timer_set_load_start(gpt, 1, 0xFFFF);

/* register the clocksource */

clocksource_register (&clocksource_gpt);

}

Clock event

This entity is used by the kernel to program the next tick event. Normally this happens every

10 msec (CLOCK_EVT_MODE_PERIODIC). In tickless and high resolution timers, it can be

used by the kernel to program the tick at the next suitable interval (even if it is longer than

than 10 msec). For that it uses two callbacks, set_mode() and set_next_event().

static struct clock_event_device clockevent_gpt = {

.name

= "clock_event",

.features

= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,

.set_mode

= clockevent_set_mode,

.set_next_event= clockevent_next_event,

.shift

= 32,

};

static void clockevent_set_mode(enum clock_event_mode mode,

struct clock_event_device* clk_event_dev )

{

u32 period;

spear_timer_stop(clk_event_tmr);

/* clear interrupt */

spear_timer_write_status(clk_event_tmr, GPT_STATUS_MATCH);

switch(mode) {

case CLOCK_EVT_MODE_PERIODIC:

/* calculate period for 10 msec timer */

...

/* program timer for 10 msec tic Enable interrupt */

spear_timer_set_match(clk_event_tmr, 1);

spear_timer_set_load_start(clk_event_tmr, 1, period);

break;

case CLOCK_EVT_MODE_ONESHOT:

* timer to be programmed for one shot, the actual programming

* period to be passed in program next event function

break;

case CLOCK_EVT_MODE_UNUSED:

case CLOCK_EVT_MODE_SHUTDOWN:

case CLOCK_EVT_MODE_RESUME:

break;

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