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

[Olof Johansson]

On Thu, Apr 30, 2015 at 8:44 AM, Kevin Hilman <khilman at kernel.org> wrote:
> Krzysztof Kozlowski <k.kozlowski at samsung.com> writes:
>
>> 2015-04-30 2:31 GMT+09:00 Kevin Hilman <khilman at kernel.org>:
>>> Krzysztof Kozlowski <k.kozlowski at samsung.com> 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 at samsung.com>
>>>> Reported-by: Javier Martinez Canillas <javier.martinez at collabora.co.uk>
>>>> Fixes: 2d2c9a8d0a4f ("ARM: dts: add display power domain for exynos5250")
>>>> Cc: <stable at vger.kernel.org>
>>>>
>>>> ---
>>>>
>>>> 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:
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1c363c7cccf64128087002b0779986ad16aff6dc
>
> 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:

http://arm-soc.lixom.net/bootlogs/mainline/v4.1-rc1-56-g3d99e3f/pi-arm-exynos_defconfig.html

Disabling CONFIG_DRM makes it boot reliably.

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


-Olof