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

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

Hi Thorsten,

On Mon, Jul 27, 2026 at 02:28:56PM +0200, Thorsten Leemhuis wrote:
> [top-posting to facilitate]
> 
> Gary, Angelo, what's the status here? It looks like this fell through
> the cracks -- or was this issue fixed in between somehow? If yes: great!
> If not: Would be good to finally resolve this, as we are long past "fix
> within a week" rule of thumb from Linus:
> https://www.kernel.org/doc/html/latest/process/handling-regressions.html#on-how-quickly-regressions-should-be-fixed

Not much happened I'm afraid. The status as I see is:
- this patch is necessary to have TI SN65DSI83 working
- this patch also follows the DRM guidelines saying that HS clock must
  be enabled during pre_enable (see previous answer / [1])
- this patch has been successfully tested against MIPI-DSI panels (by
  Angelo) and LVDS panels via TI bridge (by myself)
- Adam reported an issue with another bridge (PS8640) where resume is
  broken
- Esben offered a patch to the TI bridge that would fix the issue we
  were seeing in the first place.

But for the last two points, I'm not sure this calls for a revert yet:
- enabling HS clock in pre_enable still is what should be done [1]
- maybe the issue Adam is facing is due to the bridge driver instead as
  it could not be reproduced with another setup
- Esben patch would break the SN65DSI83 init sequence, suggesting that
  the culprit really is the MIPI bridge for not following the HS clock
  requirement in pre_enable instead [2]

So if we agree on the fact that HS clock must be set during pre_enable
then I don't see a reason to revert that commit.

Regards,
Gary

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/drm_bridge.c#n169
[2] https://patchwork.kernel.org/project/dri-devel/patch/20260711-ti-sn65dsi83-fixes-v1-2-d85eb5342b98@geanix.com/