Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Message-ID: <c888fc5e-4698-333f-6922-8b53f3efbe36@samsung.com>
Date:   Fri, 29 Oct 2021 15:36:53 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0)
        Gecko/20100101 Thunderbird/91.2.1
Subject: Re: [PATCH] arm64: Kconfig: Enable MCT timer for ARCH_EXYNOS
Content-Language: en-US
To:     Sam Protsenko <semen.protsenko@linaro.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@vger.kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Will Deacon <will@kernel.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
From:   Marek Szyprowski <m.szyprowski@samsung.com>
In-Reply-To: <CAPLW+4kKBXiwQF4qPTA04WCDb3PY365OORV4brtFxmQbSBxL8A@mail.gmail.com>
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="utf-8"
CMS-TYPE: 201P
References: <20211026115916.31553-1-semen.protsenko@linaro.org>
        <8b3466f1-2b16-80ca-79c7-577860fc90aa@canonical.com>
        <CAPLW+4=YizLzdiZ1mdCGxvPCTYhNjeiomO=q=4Xk-ZxqqH++nA@mail.gmail.com>
        <CGME20211028143524eucas1p16f240d8bc7e0d2c677fc54afde45957b@eucas1p1.samsung.com>
        <e01b0072-008a-c83d-59b2-2174860c00fd@canonical.com>
        <d4398079-e512-e75b-92e9-51d590d8c240@samsung.com>
        <CAPLW+4kKBXiwQF4qPTA04WCDb3PY365OORV4brtFxmQbSBxL8A@mail.gmail.com>
Precedence: bulk

On 29.10.2021 15:15, Sam Protsenko wrote:
> On Fri, 29 Oct 2021 at 14:38, Marek Szyprowski <m.szyprowski@samsung.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@canonical.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@linaro.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