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

[Adam Thiede <me@adamthiede.com>]

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!