On Tue, Dec 03, 2019 at 09:39:36AM +0100, Sam Ravnborg wrote:
> On Tue, Dec 03, 2019 at 08:46:59AM +0100, Maxime Ripard wrote:
> > Hi,
> >
> > On Mon, Dec 02, 2019 at 08:32:11PM +0100, Sam Ravnborg wrote:
> > > There was no users - so remove it.
> > > The callback was implemented in two drivers - deleted.
> > >
> > > Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > > Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
> > > Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > > Cc: Maxime Ripard <mripard@xxxxxxxxxx>
> > > Cc: David Airlie <airlied@xxxxxxxx>
> > > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > > ---
> > > drivers/gpu/drm/panel/panel-seiko-43wvf1g.c | 18 ------------------
> > > drivers/gpu/drm/panel/panel-simple.c | 18 ------------------
> > > include/drm/drm_panel.h | 9 ---------
> > > 3 files changed, 45 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c b/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c
> > > index b878930b17e4..3bcba64235c4 100644
> > > --- a/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c
> > > +++ b/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c
> > > @@ -217,30 +217,12 @@ static int seiko_panel_get_modes(struct drm_panel *panel,
> > > return seiko_panel_get_fixed_modes(p, connector);
> > > }
> > >
> > > -static int seiko_panel_get_timings(struct drm_panel *panel,
> > > - unsigned int num_timings,
> > > - struct display_timing *timings)
> > > -{
> > > - struct seiko_panel *p = to_seiko_panel(panel);
> > > - unsigned int i;
> > > -
> > > - if (p->desc->num_timings < num_timings)
> > > - num_timings = p->desc->num_timings;
> > > -
> > > - if (timings)
> > > - for (i = 0; i < num_timings; i++)
> > > - timings[i] = p->desc->timings[i];
> > > -
> > > - return p->desc->num_timings;
> > > -}
> > > -
> > > static const struct drm_panel_funcs seiko_panel_funcs = {
> > > .disable = seiko_panel_disable,
> > > .unprepare = seiko_panel_unprepare,
> > > .prepare = seiko_panel_prepare,
> > > .enable = seiko_panel_enable,
> > > .get_modes = seiko_panel_get_modes,
> > > - .get_timings = seiko_panel_get_timings,
> > > };
> >
> > If anything, I think we should grow the usage of timings and / or make
> > it usable by everyone.
> >
> > Using only the mode as we do currently has a bunch of shortcomings as
> > almost no encoder will be able to provide the typical pixel clock, and
> > that situation leads to multiple things:
> >
> > - If someone working on one encoder wants to upstream a panel they
> > have tested, chances are this will not be the typical pixel clock
> > / timings being used but rather the one that will match what that
> > SoC is capable of. Trouble comes when a second user comes in with
> > a different encoder and different capabilities, and then we have a
> > maintainance fight over which timing is the true timing (with a
> > significant chance that none of them are).
> >
> > - If we can't match the pixel clock, we currently have no easy way
> > to make the usual measures of reducing / growing the porches and
> > blankings areas to match the pixel clock we can provide, since we
> > don't have an easy way to get the tolerance on those timings for a
> > given panel. There's some ad hoc solutions on some drivers (I
> > think vc4 has that?) to ignore the panel and just play around with
> > the timings, but I think this should be generalised.
> >
> > Timings solves the first case since we have the operating range now
> > and not a single set of timings, and it solves the second since we can
> > use that range to take those measures instead of taking a shot in the
> > dark.
> >
> > I appreciate that it's pretty far from where we are today, but
> > removing the get_timings means that all the timings already defined in
> > the panel drivers are becoming useless too, and that eventually it
> > will get removed.
>
> Thanks for this nice explanation. I will drop the patch,
> and add an entry to my TODO list to look closer at this later.
> There are things to improve in this area.
>
> So the conclusion is more work rather than removing code :-)
Yeah, unfortunately.. :)
Maxime
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