[PATCH v6 2/4] drm/mcde: Create custom commit tail

[Linus Walleij]

On Wed, Dec 3, 2025 at 7:27 AM Chaoyi Chen <chaoyi.chen at rock-chips.com> wrote:

> The bridge document says: "The display pipe (i.e. clocks and timing
> signals) feeding this bridge will not yet be running when the
> @atomic_pre_enable is called."
>
> Therefore, your approach seems to be merely a workaround and does not
> meet the current requirements of the bridge.
>
> And document also says: "The bridge can assume that the display pipe
> (i.e. clocks and timing signals) feeding it is running when
> @atomic_enable callback is called."
>
> If DSI commands need to wait for the display pipe (CRTC) to be ready,
> why not perform them inside @atomic_enable instead of @atomic_pre_enable?

That was exactly what the v1 and v2 versions of this patch set was
doing, and it was (politely) NACKed, and that is why we are
here.
https://lore.kernel.org/dri-devel/20251023-fix-mcde-drm-regression-v1-0-ed9a925db8c7@linaro.org/
https://lore.kernel.org/dri-devel/20251026-fix-mcde-drm-regression-v2-0-8d799e488cf9@linaro.org/

In essence, Tomi remarked that drivers should be able to send DSI
commands at atomic_pre_enable() which is for example
mapped to the .prepare() callback in the DSI panel bridge.
And he has a good point in this, I just converted the few panel
drivers that I was affected by, but there are many more such
and probably some bridges as well.

Yours,
Linus Walleij