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

[Gary Bisson <bisson.gary@gmail.com>]

Hi Adam,

On Tue, Jul 07, 2026 at 08:25:41PM -0500, 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.

As a FYI here is the latest branch I tested that patch on:
https://github.com/gibsson/linux-next/commits/master-mtk/

As far as I remember suspend/resume was ok. It was tested with a
Tungsten510 SMARC SOM (MT8370) + sn65dsi83 + tm070jdhg30 display.
Both the bridge and the display are mainline, you can see that the main
change is in the defconfig where a bunch of options are changed to be
built-in (for NFS booting).

I'll try to repro against latest kernel this week and report back.

In your case, is the panel upstream as well?

Regards,
Gary