Messages in this thread | | | Date | Thu, 19 Jun 2014 18:02:45 +0200 | From | Daniel Lezcano <> | Subject | Re: [PATCH] clocksource: exynos-mct: Register the timer for stable udelay |
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On 06/19/2014 05:49 PM, Doug Anderson wrote: > Daniel, > > On Thu, Jun 19, 2014 at 2:07 AM, Daniel Lezcano > <daniel.lezcano@linaro.org> wrote: >> On 06/19/2014 01:17 AM, Doug Anderson wrote: >>> >>> Amit, >>> >>> Thanks for posting! >>> >>> On Wed, Jun 18, 2014 at 4:31 AM, Amit Daniel Kachhap >>> <amit.daniel@samsung.com> wrote: >>>> >>>> This patch register the exynos mct clocksource as the current timer >>>> as it has constant clock rate. This will generate correct udelay for the >>>> exynos platform and avoid using unnecessary calibrated jiffies. This >>>> change >>>> have been tested on exynos5420 based board. >>>> >>>> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> >>>> --- >>>> >>>> Patches from David Riley confirmed that udelay is broken in exynos5420. >>>> Link to those patches are, >>>> 1) https://patchwork.kernel.org/patch/4344911/ >>>> 2) https://patchwork.kernel.org/patch/4344881/ >>>> >>>> drivers/clocksource/exynos_mct.c | 11 +++++++++++ >>>> 1 file changed, 11 insertions(+) >>>> >>>> diff --git a/drivers/clocksource/exynos_mct.c >>>> b/drivers/clocksource/exynos_mct.c >>>> index 8d64200..57cb3dc 100644 >>>> --- a/drivers/clocksource/exynos_mct.c >>>> +++ b/drivers/clocksource/exynos_mct.c >>>> @@ -198,10 +198,21 @@ static u64 notrace exynos4_read_sched_clock(void) >>>> return exynos4_frc_read(&mct_frc); >>>> } >>>> >>>> +static struct delay_timer exynos4_delay_timer; >>>> + >>>> +static unsigned long exynos4_read_current_timer(void) >>>> +{ >>>> + return exynos4_frc_read(&mct_frc); >>> >>> >>> This is terribly inefficient to read all 64-bits and then cast back to >>> a 32-bit value. Replace with: >>> >>> return __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_L); >>> >>> >>>> +} >>>> + >>>> static void __init exynos4_clocksource_init(void) >>>> { >>>> exynos4_mct_frc_start(0, 0); >>> >>> >>> Please rebase atop (1d80415 clocksource: exynos_mct: Don't reset the >>> counter during boot and resume), which is in linuxnext among other >>> places. >>> >>>> >>>> + exynos4_delay_timer.read_current_timer = >>>> &exynos4_read_current_timer; >>>> + exynos4_delay_timer.freq = clk_rate; >>>> + register_current_timer_delay(&exynos4_delay_timer); >>>> + >>>> if (clocksource_register_hz(&mct_frc, clk_rate)) >>>> panic("%s: can't register clocksource\n", mct_frc.name); >>> >>> >>> It does seem to work for me though. :) >> >> >> Doug, >> >> aren't you working on a 32 bits version ? So this patch could be simplified > > I could do that if someone told me that they'll land it. > > My understanding of the current status is: > * I posed the 64-bit version that's almost as fast as the 32-bit version. > * I asked if people want the 32-bit version: no answer > * I asked if anyone is opposed to the 64-bit version: no answer
Yeah, that happens. I thought you were working on the 32 bits.
> I know that you wanted me to clean up the description of the 64-bit > version so I was going to do that and repost. If there's someone > willing to review / ack the 32-bit version I'd be happy to do that > instead. Possibly I'll do both and a maintainer can choose which to > apply?
Please, resend me the patch 1/3 as it is urgent with the changelog changed.
> In the case here I was suggesting using the 32-bit version just > because on ARM32 there's totally no reason to read 64-bits. I hadn't > given a thought to ARM64. More on that in response to the other > messages.
Is there a 64bits platform using exynos_mct ?
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