From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.ferre@atmel.com (Nicolas Ferre) Date: Thu, 18 Dec 2014 15:05:23 +0100 Subject: [PATCH] clocksource: timer-atmel-pit: don't suspend/resume if unused Message-ID: <1418911523-28492-1-git-send-email-nicolas.ferre@atmel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Sylvain Rochet Waiting for PIT to stop counting takes a long time: 1/(Master clock/prescaler/PIVR) = 1/(133 MHz /16 /2^20) = 126 ms Up to 126 ms if master clock is set to 133 MHz, skipping suspend/resume of the unused PIT device reduce (suspend time + resume time) from ~140 ms to ~17 ms. Signed-off-by: Sylvain Rochet [nicolas.ferre at atmel.com: move to newer clocksource driver] Signed-off-by: Nicolas Ferre Cc: Daniel Lezcano --- Hi Sylvain, I re-worked (and "Acked") your patch so it can be applied on the newer Mainline kernels. Beware, I changed the "subject line" as well. The PIT driver moved recently (3.18). Daniel, Can you take this patch in your tree? Thanks, bye. Nicolas. drivers/clocksource/timer-atmel-pit.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/clocksource/timer-atmel-pit.c b/drivers/clocksource/timer-atmel-pit.c index b5b4d4585c9a..5408bc7c68d8 100644 --- a/drivers/clocksource/timer-atmel-pit.c +++ b/drivers/clocksource/timer-atmel-pit.c @@ -123,6 +123,10 @@ static void at91sam926x_pit_suspend(struct clock_event_device *cedev) { struct pit_data *data = clkevt_to_pit_data(cedev); + /* Don't suspend PIT if unused */ + if (cedev->mode == CLOCK_EVT_MODE_UNUSED) + return; + /* Disable timer */ pit_write(data->base, AT91_PIT_MR, 0); } @@ -145,6 +149,10 @@ static void at91sam926x_pit_resume(struct clock_event_device *cedev) { struct pit_data *data = clkevt_to_pit_data(cedev); + /* Don't resume PIT if unused */ + if (cedev->mode == CLOCK_EVT_MODE_UNUSED) + return; + at91sam926x_pit_reset(data); } -- 2.1.3