From ae460fd9164b16654d8ec06cbc280b832f840eac Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 8 Jun 2021 16:43:40 +0100 Subject: [PATCH] clocksource/drivers/exynos_mct: Prioritise Arm arch timer on arm64 All arm64 CPUs feature an architected timer, which offers a relatively low-latency interface to a per-cpu clocksource and timer. For the most part, using this interface is a no-brainer, with the exception of SoCs where it cannot be used to wake up from deep idle state (i.e. CLOCK_EVT_FEAT_C3STOP is set). On the contrary, the Exynos MCT is extremely slow to access yet can be used as a wakeup source. In preparation for using the Exynos MCT as a potential wakeup timer for the Arm architected timer, reduce its ratings so that the architected timer is preferred. This effectively reverts the decision made in 6282edb72bed ("clocksource/drivers/exynos_mct: Increase priority over ARM arch timer") for arm64, as the reasoning for the original change was to work around a 32-bit SoC design. Cc: Marek Szyprowski Cc: Krzysztof Kozlowski Cc: Chanwoo Choi Cc: Thomas Gleixner Signed-off-by: Will Deacon Tested-by: Krzysztof Kozlowski # exynos-5422 Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20210608154341.10794-2-will@kernel.org --- drivers/clocksource/exynos_mct.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index fabad79..804d3e0 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -51,6 +51,15 @@ #define TICK_BASE_CNT 1 +#ifdef CONFIG_ARM +/* Use values higher than ARM arch timer. See 6282edb72bed. */ +#define MCT_CLKSOURCE_RATING 450 +#define MCT_CLKEVENTS_RATING 500 +#else +#define MCT_CLKSOURCE_RATING 350 +#define MCT_CLKEVENTS_RATING 350 +#endif + enum { MCT_INT_SPI, MCT_INT_PPI @@ -206,7 +215,7 @@ static void exynos4_frc_resume(struct clocksource *cs) static struct clocksource mct_frc = { .name = "mct-frc", - .rating = 450, /* use value higher than ARM arch timer */ + .rating = MCT_CLKSOURCE_RATING, .read = exynos4_frc_read, .mask = CLOCKSOURCE_MASK(32), .flags = CLOCK_SOURCE_IS_CONTINUOUS, @@ -457,7 +466,7 @@ static int exynos4_mct_starting_cpu(unsigned int cpu) evt->set_state_oneshot_stopped = set_state_shutdown; evt->tick_resume = set_state_shutdown; evt->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; - evt->rating = 500; /* use value higher than ARM arch timer */ + evt->rating = MCT_CLKEVENTS_RATING, exynos4_mct_write(TICK_BASE_CNT, mevt->base + MCT_L_TCNTB_OFFSET); -- 2.7.4