Re: [RFT PATCH] drm/exynos: Enable DP clock to fix display on Exynos5250 and other

From: Olof Johansson
Date: Thu Apr 30 2015 - 11:57:30 EST

On Thu, Apr 30, 2015 at 8:44 AM, Kevin Hilman <khilman@xxxxxxxxxx> wrote:
> Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx> writes:
>> 2015-04-30 2:31 GMT+09:00 Kevin Hilman <khilman@xxxxxxxxxx>:
>>> Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx> writes:
>>>> After adding display power domain for Exynos5250 in commit
>>>> 2d2c9a8d0a4f ("ARM: dts: add display power domain for exynos5250") the
>>>> display on Chromebook Snow and others stopped working after boot.
>>>> The reason for this suggested Andrzej Hajda: the DP clock was disabled.
>>>> This clock is required by Display Port and is enabled by bootloader.
>>>> However when FIMD driver probing was deferred, the display power domain
>>>> was turned off. This effectively reset the value of DP clock enable
>>>> register.
>>>> When exynos-dp is later probed, the clock is not enabled and display is
>>>> not properly configured:
>>>> exynos-dp 145b0000.dp-controller: Timeout of video streamclk ok
>>>> exynos-dp 145b0000.dp-controller: unable to config video
>>>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
>>>> Reported-by: Javier Martinez Canillas <javier.martinez@xxxxxxxxxxxxxxx>
>>>> Fixes: 2d2c9a8d0a4f ("ARM: dts: add display power domain for exynos5250")
>>>> Cc: <stable@xxxxxxxxxxxxxxx>
>>>> ---
>>>> This should fix issue reported by Javier [1][2].
>>>> Tested on Chromebook Snow (Exynos 5250). More testing would be great,
>>>> especially on other Exynos 5xxx products.
>>> I hoped to try this on my exynos5 boards, but it doesn't seem to apply
>>> to linux-next or to Linus' master branch.
>>> Are there some other dependencies here?
>> It is already applied:
> Er, yup. That would explain it. ;)
> Sorry for the noise,

Well, noise or not, Exynos is still broken in mainline and was broken
on -next for so long in different ways that bisecting it is a futile
exercise in frustration.

It doesn't seem to show up with a trivial boot using only ramdisk, but
when booting a real distro from disk, it certainly does.

For example:

Disabling CONFIG_DRM makes it boot reliably.

Arndale doesn't show it for me, but it also doesn't have working graphics.

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