linux-kernel - Re: [PATCH] arm64: Kconfig: Enable MCT timer for ARCH

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Date:   Mon, 1 Nov 2021 20:36:07 +0200
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Will Deacon <will@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH] arm64: Kconfig: Enable MCT timer for ARCH_EXYNOS

On Fri, 29 Oct 2021 at 16:36, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
>
> On 29.10.2021 15:15, Sam Protsenko wrote:
> > On Fri, 29 Oct 2021 at 14:38, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
> >> On 28.10.2021 16:35, Krzysztof Kozlowski wrote:
> >>> On 28/10/2021 16:22, Sam Protsenko wrote:
> >>>> On Tue, 26 Oct 2021 at 17:03, Krzysztof Kozlowski
> >>>> <krzysztof.kozlowski@...onical.com> wrote:
> >>>>> On 26/10/2021 13:59, Sam Protsenko wrote:
> >>>>>> Some ARM64 Exynos SoCs have MCT timer block, e.g. Exynos850 and
> >>>>>> Exynos5433. CLKSRC_EXYNOS_MCT option is not visible unless COMPILE_TEST
> >>>>>> is enabled. Select CLKSRC_EXYNOS_MCT option for ARM64 ARCH_EXYNOS like
> >>>>>> it's done in arch/arm/mach-exynos/Kconfig, to enable MCT timer support
> >>>>>> for ARM64 Exynos SoCs.
> >>>>>>
> >>>>>> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> >>>>>> ---
> >>>>>>    arch/arm64/Kconfig.platforms | 1 +
> >>>>>>    1 file changed, 1 insertion(+)
> >>>>>>
> >>>>> +CC Marek, Marc, Mark and Chanwoo,
> >>>>> Looks like duplicated:
> >>>>> https://lore.kernel.org/lkml/20181018095708.1527-7-m.szyprowski@samsung.com/
> >>>>>
> >>>>> The topic stalled and I think this particular patch did not make sense
> >>>>> on its own, without rest of changes from Marek. I am not sure, though...
> >>>>>
> >>>> Krzysztof, Marek,
> >>>>
> >>>> That series looks nice, I'm quite interested in that being applied. Do
> >>>> you think I can do something to help with that (e.g. rebasing,
> >>>> re-sending on behalf of Marek, testing on Exynos850, etc)?
> >>> I think there were no objections against v4 of this patchset, but
> >>> somehow it wasn't applied.
> >>>
> >>> Marek,
> >>> Does it make sense to try respinning your v4?
> >> I think I've abandoned it, because I got a final NACK on the arch timer
> >> change (support for 'not-fw-configured' timers). Without that the above
> >> mentioned changes doesn't make much sense.
> >>
> >> I know that the Exynos5433 firmware breaks the defined protocol, but on
> >> the other hand I can do nothing more than carrying internally those few
> >> patches out of tree to keep it fully working with 'mainline'.
> >>
> >> I've observed the same problem with newer Exynos SoCs, but those so far
> >> didn't get mainline support (yet), although there have been some
> >> attempts from the community.
> >>
> > There is no such problem on Exynos850 SoC (which I'm trying to
> > upstream right now), the architectured timer seems to be working fine
> > there, as is. Or maybe everything is configured properly in
> > bootloader, not sure. Also I managed to use MCT as a primary
> > clocksource (for sched_clock, etc) by disabling arch timer in
> > arch/arm64/kernel/time.c (just for the sake of test), and it works
> > fine.  So I still would like to have MCT enabled in kernel: this way
> > we can at least test the driver, as the clocksource can be changed to
> > MCT via sysfs (or by disabling arch timer in time.c). And for that we
> > need to at least enable CLKSRC_EXYNOS_MCT in ARCH_EXYNOS.
> MCT can be also set as default by changing its rating, like it is done
> under #ifdef CONFIG_ARM.
> > I guess all your patches (except one you mentioned) from that series
> > should be fine to apply. Do you mind if I re-send your patch series
> > (minus one patch) on your behalf? That would spare you some boring
> > work, and at least minimize your local delta you're carrying.
>
> Feel free to resend it.
>

Thanks! This patch of mine should be ignored then, I'll re-submit
Marek's patches soon.

> Best regards
>
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>