diff options
| author | Will Deacon <will@kernel.org> | 2021-06-08 18:43:40 +0300 |
|---|---|---|
| committer | Daniel Lezcano <daniel.lezcano@linaro.org> | 2021-08-13 10:24:22 +0300 |
| commit | ae460fd9164b16654d8ec06cbc280b832f840eac (patch) | |
| tree | 43fbb15aebe09c9a88bd0d9406e3118dcc4c263e /drivers/clocksource | |
| parent | f80e21489590c00f46226d5802d900e6f66e5633 (diff) | |
| download | linux-ae460fd9164b16654d8ec06cbc280b832f840eac.tar.xz | |
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 <m.szyprowski@samsung.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Will Deacon <will@kernel.org>
Tested-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> # exynos-5422
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210608154341.10794-2-will@kernel.org
Diffstat (limited to 'drivers/clocksource')
| -rw-r--r-- | drivers/clocksource/exynos_mct.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index fabad79baafc..804d3e01c8f4 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); |