Re: [PATCH] ARM: dts: remove display power domain for exynos5420

From: Rahul Sharma <rahul.sharma-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
To: Tomasz Figa <t.figa-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
Cc: Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-samsung-soc
	<linux-samsung-soc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Tomasz Figa <tomasz.figa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	sunil joshi <joshi-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	Inki Dae <inki.dae-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	Kukjin Kim <kgene.kim-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
	<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH] ARM: dts: remove display power domain for exynos5420
Date: Wed, 9 Jul 2014 17:00:07 +0530	[thread overview]
Message-ID: <CAPdUM4NGXDz-bX=qqzC7LXRE5fCapdHGZeUZ29Xov=P7VZykgg@mail.gmail.com> (raw)
In-Reply-To: <53BC0F8F.4010106-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>

Hi Tomasz,

On 8 July 2014 21:04, Tomasz Figa <t.figa-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:
> Hi Rahul,
>
> On 07.07.2014 15:37, Rahul Sharma wrote:
>> Hi Andrej, Inki,
>>
>> On 18 June 2014 12:06, Rahul Sharma <rahul.sharma-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:
>>> Hi Andrej,
>>>
>>> On 18 June 2014 11:46, Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:
>>>> On 06/17/2014 07:49 AM, Rahul Sharma wrote:
>>>>> Hi All,
>>>>>
>>>>> Please review this patch.
>>>>>
>>>>> Regards,
>>>>> Rahul Sharma
>>>>>
>>>>> On 9 June 2014 16:58, Rahul Sharma <rahul.sharma-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:
>>>>>> Display domain is removed due to instability issues. Explaining
>>>>>> the problem below:
>>>>>>
>>>>>> exynos_init_late triggers the pm_genpd_poweroff_unused which
>>>>>> powers off the unused power domains. This call hits before
>>>>>> the trigger to deferred probes.
>>>>>>
>>>>>> DRM DP Panel defers the probe due to supply get failure. By the
>>>>>> time, deferred probe is scheduled again, Display Power Domain is
>>>>>> powered off by pm_genpd_poweroff_unused.
>>>>>>
>>>>>> FIMD and DP drivers are accessing registers during Probe and Bind
>>>>>> callbacks. If display domain is enabled/disabled around register
>>>>>> accesses, display domain gets unstable and we are getting Power
>>>>>> Domain Disable fail notification. Increasing the Timeout also
>>>>>> didn't help.
>>>>
>>>> As I understand the problem is that fimd and dp drivers access hw
>>>> registers without enabling power domain. So the proper solution is to
>>>> fix these drivers.
>>>
>>> That is also a problem but I fixed those accesses in my local kernel before
>>> hitting this issue. If we do register accesses in FIMD/DP probe/bind we
>>> observes "Prefetch abort" exception. But here the problem is that 'DP
>>> domain disable' starts failing if we enable/disable multiple times.
>>>
>>>>
>>>> Btw. there are already patches removing hw access from probe/bind of
>>>> fimd. I guess removing also hw access from dp probe/bind could be a good
>>>> solution.
>>>
>>> Please let me know the links for posted patches. I will test with those patches.
>>
>> Is there any update on this? Please share the patches which fixes the
>> above issue or avoid the above scenario of multiple PM Domain enable/disable.
>> I will test them for exynos5 based boards. Otherwise we should get this change
>> merged else display will remain broken for exynos5 based boards.
>
> Andrzej is on holidays right now, so he won't be able to reply in this
> thread until he's back. Here are two patches I was able to find on the
> related MLs that might be fixing the cause of your issues:

Ok. thanks for the update.

We should test with Ajay's patches which includes DP probe deferring
based on availability of bridge chip. +

few patches which cleanup register access in FIMD and DP probe/bind
OR
few patches to enable Display power domain and clocks just before the
register access. As done in https://lkml.org/lkml/2014/7/4/188.

Later solution results into display power domain enable failure in case of DRM
probe defer.

I am just curious if Andrej has some solution for the first approach which can
be tested for defer probe and S2R scenarios.

Regards,
Rahul Sharma.

>
> [PATCH] drm/exynos: remove hardware overlays disable from fimd probe
> (https://www.mail-archive.com/linux-samsung-soc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org/msg31629.html)
>
> [PATCH] drm/exynos: fimd: Keep power enabled during fimd_bind
> (https://lkml.org/lkml/2014/7/4/188)
>
> Best regards,
> Tomasz
>
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