[PATCH v1 12/12] drm/todo: Add bridge related todo items

[Sam Ravnborg]

Hi Dave,

On Mon, Jul 18, 2022 at 11:27:37AM +0100, Dave Stevenson wrote:
> Hi Sam
> 
> On Sun, 17 Jul 2022 at 18:58, Sam Ravnborg <sam at ravnborg.org> wrote:
> >
> > Add todo in the hope someone will help updating the bridge drivers.
> >
> > v2:
> >   - Updated descriptions in todo.rst
> >
> > Signed-off-by: Sam Ravnborg <sam at ravnborg.org>
> > Acked-by: Maxime Ripard <mripard at kernel.org>
> > Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > Cc: Maxime Ripard <mripard at kernel.org>
> > Cc: Thomas Zimmermann <tzimmermann at suse.de>
> > Cc: David Airlie <airlied at linux.ie>
> > Cc: Daniel Vetter <daniel at ffwll.ch>
> > ---
> >  Documentation/gpu/todo.rst | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >
> > diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> > index 10bfb50908d1..fbcc232e0bc1 100644
> > --- a/Documentation/gpu/todo.rst
> > +++ b/Documentation/gpu/todo.rst
> > @@ -480,6 +480,26 @@ Contact: Thomas Zimmermann <tzimmermann at suse.de>
> >
> >  Level: Starter
> >
> > +Drop use of deprecated operations in bridge drivers
> > +--------------------------------------------------
> > +
> > +&struct drm_bridge_funcs contains a number of deprecated operations
> > +which can be replaced by the atomic variants.
> > +
> > +The following is more or less 1:1 replacements with the arguments
> > +and names adjusted:
> > +* pre_enable => atomic_pre_enable
> > +* enable => atomic_enable
> > +* disable => atomic_disable
> > +* post_disable => atomic_post_disable
> > +
> > +* mode_set is no longer required and the implementation shall be merged
> > +  with atomic_enable.
> 
> The dw-mipi-dsi and msm DSI host controller bridge drivers are
> currently relying on mode_set as a convenient hook to power up the DSI
> host prior to pre_enable of the bridge chain. Removing it is therefore
> going to break those.
> 
> There is a proposed mechanism to allow for the removal of this hack
> [1], but it's still waiting on R-B tags and/or discussion from bridge
> maintainers (gentle nudge as you are one of those maintainers).
I have over time gained some knowledge of how bridges works and have
applied a few patches - but the maintainer role belongs to others.
I just try to help a bit.

I will review the referenced series - could you then in return
review this series?
> 
> And do you mean merge with atomic_enable, or merge with
> atomic_pre_enable? atomic_pre_enable would be more applicable for
> almost all the bridges I'm aware of as they want to be configured
> before video starts.
Thanks, yes you are right. I will update the text to refer to
pre_enable as this is often the right choice. Looking at how many
bridges who implements mode_set, or are not yet atomic, this will
take a while before we can drop it.

	Sam