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

[Tomasz Figa <t.figa@samsung.com>]

Hi Rahul,

On 07.07.2014 15:37, Rahul Sharma wrote:
> Hi Andrej, Inki,
> 
> On 18 June 2014 12:06, Rahul Sharma <rahul.sharma@samsung.com> wrote:
>> Hi Andrej,
>>
>> On 18 June 2014 11:46, Andrzej Hajda <a.hajda@samsung.com> 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@samsung.com> 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:

[PATCH] drm/exynos: remove hardware overlays disable from fimd probe
(https://www.mail-archive.com/linux-samsung-soc@vger.kernel.org/msg31629.html)

[PATCH] drm/exynos: fimd: Keep power enabled during fimd_bind
(https://lkml.org/lkml/2014/7/4/188)

Best regards,
Tomasz