From mboxrd@z Thu Jan 1 00:00:00 1970 From: jszhang@marvell.com (Jisheng Zhang) Date: Wed, 25 Nov 2015 23:48:34 +0800 Subject: [PATCH v3 2/2] clocksource/drivers/dw_apb_timer: Use {readl|writel}_relaxed in critical path In-Reply-To: <1448466514-5298-1-git-send-email-jszhang@marvell.com> References: <1448466514-5298-1-git-send-email-jszhang@marvell.com> Message-ID: <1448466514-5298-3-git-send-email-jszhang@marvell.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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: __apbt_read_clocksource(): before the patch: 1263240ns on average after the patch: 1250080ns on average improved by 1% apbt_eoi(): before the patch: 1290960ns on average after the patch: 1248240ns on average apbt_next_event(): before the patch: 3333660ns on average after the patch: 1322040ns on average improved by 60%! Signed-off-by: Jisheng Zhang --- drivers/clocksource/dw_apb_timer.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/clocksource/dw_apb_timer.c b/drivers/clocksource/dw_apb_timer.c index 114696b..6334526 100644 --- a/drivers/clocksource/dw_apb_timer.c +++ b/drivers/clocksource/dw_apb_timer.c @@ -60,6 +60,17 @@ static inline 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; } -- 2.6.2