linux-kernel - Re: [PATCH 3/4] drm/bridge: ti-sn65dsi86: Implement bridge->mode

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Message-ID: <YRVz2MN4EDyHZYka@pendragon.ideasonboard.com>
Date:   Thu, 12 Aug 2021 22:17:44 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...omium.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] drm/bridge: ti-sn65dsi86: Implement
 bridge->mode_valid()

Hi Rob,

On Thu, Aug 12, 2021 at 12:09:12PM -0700, Rob Clark wrote:
> On Thu, Aug 12, 2021 at 11:44 AM Laurent Pinchart wrote:
> > On Wed, Aug 11, 2021 at 04:52:49PM -0700, Rob Clark wrote:
> > > From: Rob Clark <robdclark@...omium.org>
> > >
> > > For the brave new world of bridges not creating their own connectors, we
> > > need to implement the max clock limitation via bridge->mode_valid()
> > > instead of connector->mode_valid().
> > >
> > > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > > ---
> > >  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 24 +++++++++++++++++++-----
> > >  1 file changed, 19 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > > index 5d3b30b2f547..38dcc49eccaf 100644
> > > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > > @@ -595,6 +595,15 @@ static struct auxiliary_driver ti_sn_aux_driver = {
> > >       .id_table = ti_sn_aux_id_table,
> > >  };
> > >
> > > +static enum drm_mode_status check_mode(const struct drm_display_mode *mode)
> > > +{
> > > +     /* maximum supported resolution is 4K at 60 fps */
> > > +     if (mode->clock > 594000)
> > > +             return MODE_CLOCK_HIGH;
> > > +
> > > +     return MODE_OK;
> > > +}
> > > +
> > >  /* -----------------------------------------------------------------------------
> > >   * DRM Connector Operations
> > >   */
> > > @@ -616,11 +625,7 @@ static enum drm_mode_status
> > >  ti_sn_bridge_connector_mode_valid(struct drm_connector *connector,
> > >                                 struct drm_display_mode *mode)
> > >  {
> > > -     /* maximum supported resolution is 4K at 60 fps */
> > > -     if (mode->clock > 594000)
> > > -             return MODE_CLOCK_HIGH;
> > > -
> > > -     return MODE_OK;
> > > +     return check_mode(mode);
> >
> > Do we need to implement the connector .mode_valid() operation, given
> > that the bridge is linked in the chain ?
> 
> My understanding is that we need to keep it for display drivers that
> are not converted to NO_CONNECTOR..
> 
> But AFAIK snapdragon is the only upstream user of this bridge, so
> after the drm/msm/dsi patch lands we could probably garbage collect
> the connector support.

Even in the !NO_CONNECTOR case, the bridge will still be linked in the
chain, so the atomic helpers should call the bridge .mode_valid() in
addition to the connector .mode_valid(). I think the connector operation
is redundant.

> > >  }
> > >
> > >  static struct drm_connector_helper_funcs ti_sn_bridge_connector_helper_funcs = {
> > > @@ -763,6 +768,14 @@ static void ti_sn_bridge_detach(struct drm_bridge *bridge)
> > >       drm_dp_aux_unregister(&bridge_to_ti_sn65dsi86(bridge)->aux);
> > >  }
> > >
> > > +static enum drm_mode_status
> > > +ti_sn_bridge_mode_valid(struct drm_bridge *bridge,
> > > +                     const struct drm_display_info *info,
> > > +                     const struct drm_display_mode *mode)
> > > +{
> > > +     return check_mode(mode);
> > > +}
> > > +
> > >  static void ti_sn_bridge_disable(struct drm_bridge *bridge)
> > >  {
> > >       struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> > > @@ -1118,6 +1131,7 @@ static void ti_sn_bridge_post_disable(struct drm_bridge *bridge)
> > >  static const struct drm_bridge_funcs ti_sn_bridge_funcs = {
> > >       .attach = ti_sn_bridge_attach,
> > >       .detach = ti_sn_bridge_detach,
> > > +     .mode_valid = ti_sn_bridge_mode_valid,
> > >       .pre_enable = ti_sn_bridge_pre_enable,
> > >       .enable = ti_sn_bridge_enable,
> > >       .disable = ti_sn_bridge_disable,

-- 
Regards,

Laurent Pinchart