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

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Date:   Fri, 29 Oct 2021 15:36:53 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        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 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.

Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland