[PATCH 4/7] Exynos: add support for 'domain-always-on' property

[Joonyoung Shim]

Hi Marek,

On 07/01/2014 06:08 PM, Marek Szyprowski wrote:
> Hello,
>
> On 2014-07-01 10:52, Tobias Jakobi wrote:
>> Hello Marek,
>>
>> I think you had a similar patch in the tizen tree, but according to
>> Tomasz Figa, it was considered a hack. I don't quite see how this is
>> different.
>>
>> Also, if I have been following the discussion correctly, then the
>> powerdomain issue essentially is about the question which SoC block
>> needs the LCD0 domain and how the proper power on/off sequences should
>> look like.
>>
>> At least the mixer power issue, which I pointed out some time ago, seems
>> to be deal with now:
>> https://git.kernel.org/cgit/linux/kernel/git/daeinki/drm-exynos.git/commit/?h=exynos-drm-next&id=381be025ac1a6dc8efebdf146ced0d4a6007f77b 
>>
>
> Well, that patch solves power on/off sequence issue with mixer and hdmi,
> but it didn't solve the issue with additional managing of power domain
> on/off. You can check that if you remove always on property, system will
> freeze when hdmi cable is connected for the second time. I've 
> investigated
> it for some time, but right now I didn't find any 100% reliable solution
> other than keeping the power domain enabled all the time. At least for
> now, this patch lets you use HDMI without any stability issues.
>
> I've only found that there are still at least 2 issues with power 
> domains.
> One is Mixer/Video Processor dependency on LCD0 domain, second is the 
> proper

To express dependency of LCD0 domain and TV domain, how about make
master and slave hierarchy between the pm domains using
pm_genpd_add_subdomain?

> power on/off sequence of HDMI/Mixer and TV domain. Forcing both 
> domains to
> 'always on' workarounds both issues for now. Right now I have no better
> idea.
>
> Later, once the proper sequence is found we can remove those properties
> from Odroid DTS.
>
> Best regards