Messages in this thread | | | Date | Mon, 21 Jun 2021 11:10:59 +0100 | From | Will Deacon <> | Subject | Re: [PATCH 1/2] clocksource/drivers/exynos_mct: Prioritise Arm arch timer on arm64 |
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On Mon, Jun 21, 2021 at 11:25:47AM +0200, Daniel Lezcano wrote: > On 17/06/2021 23:47, Will Deacon wrote: > > On Thu, Jun 17, 2021 at 09:58:35AM +0900, Chanwoo Choi wrote: > >> On 6/17/21 12:25 AM, Daniel Lezcano wrote: > >>> On 10/06/2021 03:03, Chanwoo Choi wrote: > >>>> On 6/9/21 12:43 AM, Will Deacon wrote: > >>>>> 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); > >>>>> > >>>>> > >>>> > >>>> I'm not sure that exynos mct is working without problem > >>>> such as the case of 6282edb72bed. > >>>> As described on On ,6282edb72bed the arch timer on exynos SoC > >>>> depends on Exynos MCT device. the arch timer is not able to work > >>>> without Exynos MCT because of using the common module. > >>> > >>> Is it possible to change the DT to have a phandle to the exynos_mct, so > >>> it will be probed before the arch_arm_timer ? > >> > >> I think that DT changes is not proper way to keep the order between > >> exynos_mct and arch timer. > > > > exynos4_mct_frc_start() is called unconditionally from probe via > > exynos4_clocksource_init() so as long as the mct probes first, then the > > arch timer should work, no? The rating shouldn't affect that. > > How do you ensure the exynos mct is probed before the arch timer ? > > The Makefile provides the right order, but the dependency is implicit.
Currently, I think it's done by the order of the CPU hotplug notifiers ( see the hunk of 6282edb72bed which touches cpuhotplug.h).
Will
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