[PATCH 2/3] drm/msm/dsi: move next bridge acquisition to dsi_bind

[Dmitry Baryshkov]

On Fri, 5 Apr 2024 at 20:35, Abhinav Kumar <quic_abhinavk at quicinc.com> wrote:
>
>
>
> On 3/9/2024 7:09 AM, Dmitry Baryshkov wrote:
> > Currently the MSM DSI driver looks for the next bridge during
> > msm_dsi_modeset_init(). If the bridge is not registered at that point,
> > this might result in -EPROBE_DEFER, which can be problematic that late
> > during the device probe process. Move next bridge acquisition to the
> > dsi_bind state so that probe deferral is returned as early as possible.
> >
>
> But msm_dsi_modeset)init() is also called during msm_drm_bind() only.
>
> What issue are you suggesting will be fixed by moving this from
> msm_drm_bind() to dsi_bind()?

The goal is to return as early as possible as not not cause
probe-deferral loops. See commit fbc35b45f9f6 ("Add documentation on
meaning of -EPROBE_DEFER"). It discusses returning from probe() but
the same logic applies to bind().

> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> > ---
> >   drivers/gpu/drm/msm/dsi/dsi.c         | 16 ++++++++++++++++
> >   drivers/gpu/drm/msm/dsi/dsi.h         |  2 ++
> >   drivers/gpu/drm/msm/dsi/dsi_manager.c |  8 +-------
> >   3 files changed, 19 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dsi/dsi.c b/drivers/gpu/drm/msm/dsi/dsi.c
> > index 37c4c07005fe..38f10f7a10d3 100644
> > --- a/drivers/gpu/drm/msm/dsi/dsi.c
> > +++ b/drivers/gpu/drm/msm/dsi/dsi.c
> > @@ -120,6 +120,22 @@ static int dsi_bind(struct device *dev, struct device *master, void *data)
> >       struct msm_drm_private *priv = dev_get_drvdata(master);
> >       struct msm_dsi *msm_dsi = dev_get_drvdata(dev);
> >
> > +     /*
> > +      * Next bridge doesn't exist for the secondary DSI host in a bonded
> > +      * pair.
> > +      */
> > +     if (!msm_dsi_is_bonded_dsi(msm_dsi) ||
> > +         msm_dsi_is_master_dsi(msm_dsi)) {
> > +             struct drm_bridge *ext_bridge;
> > +
> > +             ext_bridge = devm_drm_of_get_bridge(&msm_dsi->pdev->dev,
> > +                                                 msm_dsi->pdev->dev.of_node, 1, 0);
> > +             if (IS_ERR(ext_bridge))
> > +                     return PTR_ERR(ext_bridge);
> > +
> > +             msm_dsi->next_bridge = ext_bridge;
> > +     }
> > +
> >       priv->dsi[msm_dsi->id] = msm_dsi;
> >
> >       return 0;
> > diff --git a/drivers/gpu/drm/msm/dsi/dsi.h b/drivers/gpu/drm/msm/dsi/dsi.h
> > index 2ad9a842c678..0adef65be1de 100644
> > --- a/drivers/gpu/drm/msm/dsi/dsi.h
> > +++ b/drivers/gpu/drm/msm/dsi/dsi.h
> > @@ -38,6 +38,8 @@ struct msm_dsi {
> >       struct mipi_dsi_host *host;
> >       struct msm_dsi_phy *phy;
> >
> > +     struct drm_bridge *next_bridge;
> > +
> >       struct device *phy_dev;
> >       bool phy_enabled;
> >
> > diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> > index a7c7f85b73e4..b7c52b14c790 100644
> > --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> > +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> > @@ -464,18 +464,12 @@ int msm_dsi_manager_ext_bridge_init(u8 id, struct drm_bridge *int_bridge)
> >       struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
> >       struct drm_device *dev = msm_dsi->dev;
> >       struct drm_encoder *encoder;
> > -     struct drm_bridge *ext_bridge;
> >       struct drm_connector *connector;
> >       int ret;
> >
> > -     ext_bridge = devm_drm_of_get_bridge(&msm_dsi->pdev->dev,
> > -                                         msm_dsi->pdev->dev.of_node, 1, 0);
> > -     if (IS_ERR(ext_bridge))
> > -             return PTR_ERR(ext_bridge);
> > -
> >       encoder = int_bridge->encoder;
> >
> > -     ret = drm_bridge_attach(encoder, ext_bridge, int_bridge,
> > +     ret = drm_bridge_attach(encoder, msm_dsi->next_bridge, int_bridge,
> >                       DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> >       if (ret)
> >               return ret;
> >



-- 
With best wishes
Dmitry