Re: [PATCH] drm/mediatek: mtk_dsi: enable hs clock during pre-enable

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

On 7/8/26 03:25, Adam Thiede wrote:
> On 7/7/26 05:38, AngeloGioacchino Del Regno wrote:
>> On 7/7/26 10:51, Thorsten Leemhuis wrote:
>>> On 7/7/26 04:20, CK Hu (胡俊光) wrote:
>>>> On Mon, 2026-07-06 at 12:16 +0200, Thorsten Leemhuis wrote:
>>>>> On 6/22/26 15:23, Adam Thiede wrote:
>>>>>> On 6/22/26 06:22, Gary Bisson wrote:
>>>>>>> On Thu, Jun 18, 2026 at 04:06:28PM -0500, Adam Thiede wrote:
>>>>>>>> On 1/20/26 05:36, Gary Bisson wrote:
>>>>>>>>> Some bridges, such as the TI SN65DSI83, require the HS clock to be
>>>>>>>>> running in order to lock its PLL during its own pre-enable function.
>>>>>>>>>
>>>>>>>>> Without this change, the bridge gives the following error:
>>>>>>>>> sn65dsi83 14-002c: failed to lock PLL, ret=-110
>>>>>>>>> sn65dsi83 14-002c: Unexpected link status 0x01
>>>>>>>>> sn65dsi83 14-002c: reset the pipe
>>>>>>>>> [...]
>>>>>>>>
>>>>>>>> This commit was part of 7.1 and caused a problem for me.
>>>>>>>> I'm running postmarketOS (basically Alpine Linux) on a Lenovo C330
>>>>>>>> chromebook with a Mediatek MT8173 processor.
>>>>>>>> The problem: when the display on my laptop powers off (via suspend or
>>>>>>>> idle,
>>>>>>>> like xset dpms off) the picture does not come back when the display
>>>>>>>> powers
>>>>>>>> back on (from resume). The display backlight comes on and brightness is
>>>>>>>> adjustable but there is no picture. The only fix is to reboot.
>>>>>>>>
>>>>>>>> Reverting this commit and applying it as a patch on top of 7.1
>>>>>>>> addresses the
>>>>>>>> issue for me.
>>>>>>>>
>>>>>>>> You can view the config I'm using here:
>>>>>>>> https://urldefense.com/v3/__https://gitlab.postmarketos.org/ postmarketOS/ 
>>>>>>>> pmaports/-/__;!!CTRNKA9wMg0ARbw! 
>>>>>>>> jrsPDtSEUdaINzLlq92Li8gmsEBkTOxZ6WUzNHjvIN6CyOJjHiHkNSOhIRPXFTLPlaYlxU2uvryVkwjUAN9bmax5$
>>>>>>>> merge_requests/8819
>>>>>>>>
>>>>>>>> Is there any sort of testing or other debugging info I can provide to
>>>>>>>> help
>>>>>>>> address this issue?
>>>>>>>
>>>>>>> Thanks for reporting the issue, could you share some logs? Is the driver
>>>>>>> saying anything during resume? Also, what type of panel is used on that
>>>>>>> chromebook?
>>>>>>
>>>>>> The curious thing is that there are no real logs in dmesg or /var/log/
>>>>>> messages about this. This picture just fails to come back. If there are
>>>>>> some kernel params I can set to get deeper logging, that would help, but
>>>>>> I'm not aware of any.
>>>>>>
>>>>>> I think the panel is a "BOE NV116WHM-T00" - I used this command to get
>>>>>> info: cat /sys/class/drm/card0-eDP-1/edid | edid-decode
>>>>>>
>>>>>> Output: https://urldefense.com/v3/__https://termbin.com/8nbd__;!! 
>>>>>> CTRNKA9wMg0ARbw! 
>>>>>> jrsPDtSEUdaINzLlq92Li8gmsEBkTOxZ6WUzNHjvIN6CyOJjHiHkNSOhIRPXFTLPlaYlxU2uvryVkwjUAJooSyqL$
>>>>>
>>>>> This looked stalled. If I'm mistaken here, please let me known; but if
>>>>> no solution is in sight, should we maybe just revert the change until a
>>>>> proper was found?
>>>>
>>>> It's welcome anyone to provide a revert patch,
>>>> but I would still wait for the fixup patch until 7.2-rc4.
>>>> If no fixup patch exist, then apply the revert patch.
>>>  From my understanding of things the position in the devel cycle doesn't
>>> matter much in a case like this. To quote Linus statements from
>>> https://www.kernel.org/doc/html/latest/process/handling- regressions.html#on- 
>>> how-quickly-regressions-should-be-fixed
>>>
>>> """
>>>  From 2026-01-22:
>>>
>>>   But a user complaining should basically result in an immediate fix -
>>>   possibly a "revert and rethink".
>>>
>>> With a later clarification on 2026-01-28:
>>>
>>>   It's also worth noting that "immediate" obviously doesn't mean "right
>>>   this *second* when the problem has been reported".
>>>
>>>   But if it's a regression with a known commit that caused it, I think
>>>   the rule of thumb should generally be "within a week", preferably
>>>   before the next rc.
>>> """
>>>
>>> Adam reported the problem about three weeks ago, so we are way past the
>>> "rule of thumb" timeframe Linus set.
>>>
>>> Ciao, Thorsten
>>
>> This is a kind of odd situation here. The fix from Adam is actually correct, as in,
>> the SN65DSI83 bridge gets broken without...
>>
>> ....but then, there's some more oddness going on: I tried to reproduce this on my
>> MT8173 Elm device, but there I can resume the system just fine, and the display is
>> up and running like normal?
>>
>> I'm not sure what to advice here at this point - just adding some info.
>>
>> Cheers,
>> Angelo
> Angelo, would you mind sharing your config, and the details of what you're running? 
> It might be a configuration difference.
> Thanks!

Sure, here it is:

https://gitlab.collabora.com/mediatek/aiot/linux/-/blob/mediatek-dev/arch/arm64/configs/defconfig?ref_type=heads

Cheers,
Angelo