[PATCH] ARM: exynos_defconfig: disable CONFIG_EXYNOS5420_MCPM; not stable

[Kevin Hilman]

On Mon, Nov 24, 2014 at 5:37 PM, Olof Johansson <olof at lixom.net> wrote:
> On Mon, Nov 24, 2014 at 5:35 PM, Kevin Hilman <khilman at kernel.org> wrote:
>> On Mon, Nov 24, 2014 at 4:25 PM, Olof Johansson <olof at lixom.net> wrote:
>>> On Mon, Nov 24, 2014 at 11:51 AM, Kevin Hilman <khilman at kernel.org> wrote:
>>>> Kukjin,
>>>>
>>>> On Mon, Nov 10, 2014 at 11:35 AM, Kevin Hilman <khilman at kernel.org> wrote:
>>>>> Kukjin Kim <kgene at kernel.org> writes:
>>>>>
>>>>>> Kevin Hilman wrote:
>>>>>>>
>>>>>>> From: Kevin Hilman <khilman at linaro.org>
>>>>>>>
>>>>>>> The option CONFIG_EXYNOS5420_MCPM is causing imprecise external aborts
>>>>>>> during boot testing, causing various userspace startup failures.
>>>>>>>
>>>>>>> Disable until it has gotten more testing.
>>>>>>>
>>>>>>> Cc: Kukjin Kim <kgene.kim at samsung.com>,
>>>>>>> Cc: Javier Martinez Canillas <javier.martinez at collabora.co.uk>,
>>>>>>> Cc: Sachin Kamat <sachin.kamat at samsung.com>,
>>>>>>> Cc: Doug Anderson <dianders at chromium.org>,
>>>>>>> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie at samsung.com>,
>>>>>>> Cc: Krzysztof Kozlowski <k.kozlowski at samsung.com>,
>>>>>>> Cc: Tushar Behera <tushar.behera at linaro.org>,
>>>>>>> Cc: stable at vger.kernel.org # v3.17+
>>>>>>> Signed-off-by: Kevin Hilman <khilman at linaro.org>
>>>>>>> ---
>>>>>>> This has been reported by a few people[1], but not investigated or fixed, so it's
>>>>>>> time to disable this feature until it can be fixed.
>>>>>>>
>>>>>> Hi Kevin,
>>>>>>
>>>>>> Yeah I agree with your opinion.
>>>>>>
>>>>>> But as you can see my tree, I've queued regarding mcpm patches for 3.19 will
>>>>>> be shown in -next in this weekend.
>>>>>
>>>>> Which of the recently queued patches are expected to address the
>>>>> imprecise abort issue?  I'd be happy to test them out.
>>>>
>>>> Exynos5 MCPM is still broken in linux-next and still causing an imprecise abort.
>>>>
>>>> What is the status of $SUBJECT patch?
>>>>
>>>>>> Anyway let me apply this into -fixes and
>>>>>> then let's enable after test its functionality in -next in a couple of days.
>>>>>
>>>>> Yes, I think this needs to be applied until these aborts are understood
>>>>> and fixed.
>>>>
>>>> Is anyone at Samsung actually looking into these MCPM issues?
>>>
>>> Hi Kevin,
>>>
>>> What hardware are you having problems with? 5420 or 5422/5800?
>>
>> Yes.  :)
>>
>> exynos5420-arndale-octa:
>> http://storage.armcloud.us/kernel-ci/mainline/v3.18-rc6/arm-exynos_defconfig/boot-exynos5420-arndale-octa.html
>> exynos5422-odroid-xu3:
>> http://storage.armcloud.us/kernel-ci/mainline/v3.18-rc6/arm-exynos_defconfig/boot-exynos5422-odroid-xu3.html
>>
>> My boot tests seem to pass fine because I have such a minimal
>> userspace, but Tyler Baker reported that with a "real" userspace, he
>> can't boot to a shell:
>>
>>   http://lists.infradead.org/pipermail/linux-arm-kernel/2014-September/286203.html
>
> I'm not surprised that 5420 has issues, but I have not seen any
> external aborts on neither Chromebook that I have in my farm.
>
> Sounds like the secondary cpus should be disabled on those device
> trees instead, doesn't it?

That's possible.

Unfortunately, I've gotten very little support from Samsung on this
and it was originally reported 2.5 months ago[2], so I think that the
5420 MCPM should be disabled until they can propose the right fix, and
actually test it.

Also, I tried disabling some CPUs at boot time, but the
exynos5422-odroid-xu3 wont' even boot with nr_cpus=1 or 4 (or anything
less than 8)

Kevin

[1]  http://lists.infradead.org/pipermail/linux-arm-kernel/2014-September/286203.html