Re: [PATCH v3 2/9] drm/mediatek: dp: Move AUX and panel poweron/off sequence to function

[AngeloGioacchino Del Regno]

Il 06/04/23 10:20, Chen-Yu Tsai ha scritto:
> On Tue, Apr 4, 2023 at 6:48 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:
> > Everytime we run bridge detection and/or EDID read we run a poweron
> > and poweroff sequence for both the AUX and the panel; moreover, this
> > is also done when enabling the bridge in the .atomic_enable() callback.
> >
> > Move this power on/off sequence to a new mtk_dp_aux_panel_poweron()
> > function as to commonize it.
> > Note that, before this commit, in mtk_dp_bridge_atomic_enable() only
> > the AUX was getting powered on but the panel was left powered off if
> > the DP cable wasn't plugged in while now we unconditionally send a D0
> > request and this is done for two reasons:
> >   - First, whether this request fails or not, it takes the same time
> >     and anyway the DP hardware won't produce any error (or, if it
> >     does, it's ignorable because it won't block further commands)
> >   - Second, training the link between a sleeping/standby/unpowered
> >     display makes little sense.
> >
> > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/mediatek/mtk_dp.c | 76 ++++++++++++-------------------
> >   1 file changed, 30 insertions(+), 46 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> > index 84f82cc68672..76ea94167531 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> > @@ -1253,6 +1253,29 @@ static void mtk_dp_audio_mute(struct mtk_dp *mtk_dp, bool mute)
> >                             val[2], AU_TS_CFG_DP_ENC0_P0_MASK);
> >   }
> >
> > +static void mtk_dp_aux_panel_poweron(struct mtk_dp *mtk_dp, bool pwron)
> > +{
> > +       if (pwron) {
> > +               /* power on aux */
> > +               mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> > +                                  DP_PWR_STATE_BANDGAP_TPLL_LANE,
> > +                                  DP_PWR_STATE_MASK);
> > +
> > +               /* power on panel */
> > +               drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
> > +               usleep_range(2000, 5000);
> > +       } else {
> > +               /* power off panel */
> > +               drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D3);
> > +               usleep_range(2000, 3000);
> > +
> > +               /* power off aux */
> > +               mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> > +                                  DP_PWR_STATE_BANDGAP_TPLL,
> > +                                  DP_PWR_STATE_MASK);
> > +       }
> > +}
> > +
> >   static void mtk_dp_power_enable(struct mtk_dp *mtk_dp)
> >   {
> >          mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_RESET_AND_PROBE,
> > @@ -1937,16 +1960,9 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
> >          if (!mtk_dp->train_info.cable_plugged_in)
> >                  return ret;
> >
> > -       if (!enabled) {
> > -               /* power on aux */
> > -               mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> > -                                  DP_PWR_STATE_BANDGAP_TPLL_LANE,
> > -                                  DP_PWR_STATE_MASK);
> > +       if (!enabled)
> > +               mtk_dp_aux_panel_poweron(mtk_dp, true);
> >
> > -               /* power on panel */
> > -               drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
>
> I suspect the original code was somewhat wrong already? We shouldn't need
> to pull the panel out of standby just for HPD or reading EDID.
>
> This driver probably needs a lot more cleanup. :/

I believe the same... but I wanted to play safe, as I don't know if there's any
panel in particular that requires such quirk...

Angelo