Re: [PATCH] drm/panel-edp: Add pre_unprepare delay

[Hsin-Te Yuan]

On Tue, Aug 4, 2026 at 3:50 AM Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Mon, Aug 3, 2026 at 2:47 AM Hsin-Te Yuan <yuanhsinte@xxxxxxxxxxxx> wrote:
> >
> > In eDP power-off timing specifications, T10 defines the minimum delay
> > required between the end of valid video data from the source and panel
> > power-down (main VDD off).
> >
> > Currently, panel-edp only supports the 'disable' delay, which corresponds
> > to T9 (backlight off to end of video data) and runs in panel_edp_disable()
> > while video data is still active. For panels that require a delay after
> > video data has stopped before cutting power, this delay must occur in
> > panel_edp_unprepare() before turning off power rails.
> >
> > Add a 'pre_unprepare' field to struct panel_delay to model T10-min, and
> > delay for this duration in panel_edp_unprepare() before calling
> > pm_runtime_put_sync_suspend().
> >
> > Additionally, adjust the timing entry for TM156VDXP25 to use
> > delay_200_500_e80_pu100 (enable = 80ms, pre_unprepare = 100ms) to match
> > its panel specification, replacing the previous delay_200_500_e50_d100.
> >
> > Fixes: b9e2d5cdaab0 ("drm/panel-edp: Support NV140FHM-N5B and TM156VDXP25")
> > Signed-off-by: Hsin-Te Yuan <yuanhsinte@xxxxxxxxxxxx>
> > ---
> > Change-Id: I3361bdf4d3289c773f0c2b77163e427b774797d5
> > ---
> >  drivers/gpu/drm/panel/panel-edp.c | 23 ++++++++++++++++++++++-
> >  1 file changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> > index 98bdcf352701..f6624191f97c 100644
> > --- a/drivers/gpu/drm/panel/panel-edp.c
> > +++ b/drivers/gpu/drm/panel/panel-edp.c
> > @@ -144,6 +144,16 @@ struct panel_delay {
> >          */
> >         unsigned int disable;
> >
> > +       /**
> > +        * @pre_unprepare: Time for the end of video data to power off.
> > +        *
> > +        * The time (in milliseconds) that it needs to have passed between
> > +        * the end of valid video data from source and start powering off.
> > +        *
> > +        * This is T10-min on eDP timing diagrams. It is not common to set.
> > +        */
> > +       unsigned int pre_unprepare;
> > +
> >         /**
> >          * @unprepare: Time to power down completely.
> >          *
> > @@ -413,8 +423,12 @@ static int panel_edp_suspend(struct device *dev)
> >
> >  static int panel_edp_unprepare(struct drm_panel *panel)
> >  {
> > +       struct panel_edp *p = to_panel_edp(panel);
> >         int ret;
> >
> > +       if (p->desc->delay.pre_unprepare)
> > +               msleep(p->desc->delay.pre_unprepare);
> > +
> >         ret = pm_runtime_put_sync_suspend(panel->dev);
> >         if (ret < 0)
> >                 return ret;
> > @@ -1810,6 +1824,13 @@ static const struct panel_delay delay_80_500_e80_p2e200 = {
> >         .prepare_to_enable = 200,
> >  };
> >
> > +static const struct panel_delay delay_200_500_e80_pu100 = {
> > +       .hpd_absent = 200,
> > +       .unprepare = 500,
> > +       .enable = 80,
> > +       .pre_unprepare = 100,
> > +};
> > +
> >  static const struct panel_delay delay_100_500_e200 = {
> >         .hpd_absent = 100,
> >         .unprepare = 500,
> > @@ -2181,7 +2202,7 @@ static const struct edp_panel_entry edp_panels[] = {
> >
> >         EDP_PANEL_ENTRY('T', 'M', 'A', 0x0811, &delay_200_500_e80_d50, "TM140VDXP01-04"),
> >         EDP_PANEL_ENTRY('T', 'M', 'A', 0x2094, &delay_200_500_e50_d100, "TL140VDMS03-01"),
> > -       EDP_PANEL_ENTRY('T', 'M', 'A', 0x2139, &delay_200_500_e50_d100, "TM156VDXP25"),
> > +       EDP_PANEL_ENTRY('T', 'M', 'A', 0x2139, &delay_200_500_e80_pu100, "TM156VDXP25"),
>
> Looks OK to me. Thank you for the thorough description.
>
> Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
>
> Do you happen to know if any of the other TMA panels should also get
> this updated timing?
>
No, this is the only one the ODM reported so far.
>
> My thought would be to land this in drm-misc-next instead of
> drm-misc-fixes. Is that OK w/ you? I assume you just need a stable git
> hash to pick and it's not urgent for you to get this in through stable
> trees. Getting the updated timings is usually not massively
> time-critical and having bake time / avoiding merge conflicts is
> nice...
Yes, I'm fine with that. Actually the original commit is still in drm-misc-next,
so I guess this can't be landed in drm-misc-fixes.
>
> Assuming nothing else comes up, I'll try to land in the next few days.
> Usually I don't delay at all for panel timings, but since this changes
> an old panel I'll at least give it an extra day or two...
>
> -Doug

Regards,
Hsin-Te