linux-kernel - Re: [PATCH v2 3/3] drm/bridge: ti-sn65dsi86: Add NO

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Date:   Thu, 23 Sep 2021 10:31:52 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.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 v2 3/3] drm/bridge: ti-sn65dsi86: Add NO_CONNECTOR support

On Wed, Sep 22, 2021 at 5:44 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Rob,
>
> Thank you for the patch.
>
> On Mon, Sep 20, 2021 at 03:58:00PM -0700, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > Slightly awkward to fish out the display_info when we aren't creating
> > own connector.  But I don't see an obvious better way.
> >
> > v2: Remove error return with NO_CONNECTOR flag
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > ---
> >  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 39 ++++++++++++++++++++-------
> >  1 file changed, 29 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > index 6154bed0af5b..94c94cc8a4d8 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > @@ -667,11 +667,6 @@ static int ti_sn_bridge_attach(struct drm_bridge *bridge,
> >                                                  .node = NULL,
> >                                                };
> >
> > -     if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
> > -             DRM_ERROR("Fix bridge driver to make connector optional!");
> > -             return -EINVAL;
> > -     }
> > -
> >       pdata->aux.drm_dev = bridge->dev;
> >       ret = drm_dp_aux_register(&pdata->aux);
> >       if (ret < 0) {
> > @@ -679,9 +674,11 @@ static int ti_sn_bridge_attach(struct drm_bridge *bridge,
> >               return ret;
> >       }
> >
> > -     ret = ti_sn_bridge_connector_init(pdata);
> > -     if (ret < 0)
> > -             goto err_conn_init;
> > +     if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
> > +             ret = ti_sn_bridge_connector_init(pdata);
> > +             if (ret < 0)
> > +                     goto err_conn_init;
> > +     }
> >
> >       /*
> >        * TODO: ideally finding host resource and dsi dev registration needs
> > @@ -743,7 +740,8 @@ static int ti_sn_bridge_attach(struct drm_bridge *bridge,
> >  err_dsi_attach:
> >       mipi_dsi_device_unregister(dsi);
> >  err_dsi_host:
> > -     drm_connector_cleanup(&pdata->connector);
> > +     if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> > +             drm_connector_cleanup(&pdata->connector);
>
> I wonder if we actually need this. The connector gets attached to the
> encoder, won't it be destroyed by the DRM core in the error path ?

This does not appear to be the case, we leak the connector if I remove
this (and add a hack to trigger the error path)

> >  err_conn_init:
> >       drm_dp_aux_unregister(&pdata->aux);
> >       return ret;
> > @@ -792,9 +790,30 @@ static void ti_sn_bridge_set_dsi_rate(struct ti_sn65dsi86 *pdata)
> >       regmap_write(pdata->regmap, SN_DSIA_CLK_FREQ_REG, val);
> >  }
> >
> > +/*
> > + * Find the connector and fish out the bpc from display_info.  It would
> > + * be nice if we could get this instead from drm_bridge_state, but that
> > + * doesn't yet appear to be the case.
>
> You already have a bus format in the bridge state, from which you can
> derive the bpp. Could you give it a try ?

Possibly the bridge should be converted to ->atomic_enable(), etc..
I'll leave that for another time

BR,
-R

> > + */
> >  static unsigned int ti_sn_bridge_get_bpp(struct ti_sn65dsi86 *pdata)
> >  {
> > -     if (pdata->connector.display_info.bpc <= 6)
> > +     struct drm_bridge *bridge = &pdata->bridge;
> > +     struct drm_connector_list_iter conn_iter;
> > +     struct drm_connector *connector;
> > +     unsigned bpc = 0;
> > +
> > +     drm_connector_list_iter_begin(bridge->dev, &conn_iter);
> > +     drm_for_each_connector_iter(connector, &conn_iter) {
> > +             if (drm_connector_has_possible_encoder(connector, bridge->encoder)) {
> > +                     bpc = connector->display_info.bpc;
> > +                     break;
> > +             }
> > +     }
> > +     drm_connector_list_iter_end(&conn_iter);
> > +
> > +     WARN_ON(bpc == 0);
> > +
> > +     if (bpc <= 6)
> >               return 18;
> >       else
> >               return 24;
>
> --
> Regards,
>
> Laurent Pinchart