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clocksource/drivers/dw_apb_timer: Use {readl|writel}_relaxed in critical path

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It's safe to use the relaxed version. From another side, the relaxed io
accessor macros are available on all architectures now, so we can use
the relaxed versions to get a trivial system performance improvement,
we measured time the following functions spent on Marvell BG4CT:

4096 rounds of __apbt_read_clocksource() call:

before the patch: 1263240ns on average
after the patch: 1250080ns on average
improved by 1%

4096 rounds of apbt_eoi() call:

before the patch: 1290960ns on average
after the patch: 1248240ns on average

4096 rounds of apbt_next_event() call:

before the patch: 3333660ns on average
after the patch: 1322040ns on average

improved by 60%!

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
This commit is contained in:
Jisheng Zhang 2015-11-26 00:01:53 +08:00 committed by Daniel Lezcano
parent 9f4165dc4e
commit 39d3611f2d
1 changed files with 18 additions and 6 deletions
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24
drivers/clocksource/dw_apb_timer.c
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@ -60,6 +60,17 @@ static void apbt_writel(struct dw_apb_timer *timer, u32 val,
writel(val, timer->base + offs);
}
static inline u32 apbt_readl_relaxed(struct dw_apb_timer *timer, unsigned long offs)
{
return readl_relaxed(timer->base + offs);
}
static inline void apbt_writel_relaxed(struct dw_apb_timer *timer, u32 val,
unsigned long offs)
{
writel_relaxed(val, timer->base + offs);
}
static void apbt_disable_int(struct dw_apb_timer *timer)
{
u32 ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
@ -81,7 +92,7 @@ void dw_apb_clockevent_pause(struct dw_apb_clock_event_device *dw_ced)
static void apbt_eoi(struct dw_apb_timer *timer)
{
apbt_readl(timer, APBTMR_N_EOI);
apbt_readl_relaxed(timer, APBTMR_N_EOI);
}
static irqreturn_t dw_apb_clockevent_irq(int irq, void *data)
@ -200,13 +211,13 @@ static int apbt_next_event(unsigned long delta,
struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
/* Disable timer */
ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
ctrl = apbt_readl_relaxed(&dw_ced->timer, APBTMR_N_CONTROL);
ctrl &= ~APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
apbt_writel_relaxed(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
/* write new count */
apbt_writel(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT);
apbt_writel_relaxed(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT);
ctrl |= APBTMR_CONTROL_ENABLE;
apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
apbt_writel_relaxed(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
return 0;
}
@ -342,7 +353,8 @@ static cycle_t __apbt_read_clocksource(struct clocksource *cs)
struct dw_apb_clocksource *dw_cs =
clocksource_to_dw_apb_clocksource(cs);
current_count = apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE);
current_count = apbt_readl_relaxed(&dw_cs->timer,
APBTMR_N_CURRENT_VALUE);
return (cycle_t)~current_count;
}