Re: [PATCH v5 3/7] drm: sun4i: dsi: Convert to bridge driver

[Maxime Ripard <maxime@cerno.tech>]

On Mon, Nov 22, 2021 at 07:18:13PM +0530, Jagan Teki wrote:
> Hi Maxime,
> 
> On Mon, Nov 22, 2021 at 3:37 PM Maxime Ripard <maxime@cerno.tech> wrote:
> >
> > On Mon, Nov 22, 2021 at 12:22:19PM +0530, Jagan Teki wrote:
> > > Some display panels would come up with a non-DSI output, those
> > > can have an option to connect the DSI host by means of interface
> > > bridge converter.
> > >
> > > This DSI to non-DSI interface bridge converter would requires
> > > DSI Host to handle drm bridge functionalities in order to DSI
> > > Host to Interface bridge.
> >
> > In order to do this you would need to use the DRM bridge API...
> 
> Sorry, which bridge API do you mean?

Any variant of of_drm_find_bridge, and drm_bridge_attach. Just like
we're doing in sun4i_rgb.c

> > > This patch convert the existing to a drm bridge driver with a
> > > built-in encoder support for compatibility with existing
> > > component drivers.
> >
> > ... but changing the encoder driver to a bridge is completely
> > unnecessary to do so. Why did you need to make that change?
> 
> Idea of this series is to convert the driver to bridge and use the
> latest bridge function from the v1 series.

Ok, but it's not at all what you mention in your commit log? You don't
need any of that in order to support a bridge downstream.

> >
> > > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > >
> > > ---
> > > Changes for v5:
> > > - add atomic APIs
> > > - find host and device variant DSI devices.
> > > Changes for v4, v3:
> > > - none
> > >
> > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 112 ++++++++++++++++++++-----
> > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |   7 ++
> > >  2 files changed, 96 insertions(+), 23 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > index 43d9c9e5198d..a6a272b55f77 100644
> > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > @@ -21,6 +21,7 @@
> > >
> > >  #include <drm/drm_atomic_helper.h>
> > >  #include <drm/drm_mipi_dsi.h>
> > > +#include <drm/drm_of.h>
> > >  #include <drm/drm_panel.h>
> > >  #include <drm/drm_print.h>
> > >  #include <drm/drm_probe_helper.h>
> > > @@ -713,10 +714,11 @@ static int sun6i_dsi_start(struct sun6i_dsi *dsi,
> > >       return 0;
> > >  }
> > >
> > > -static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> > > +static void sun6i_dsi_bridge_atomic_enable(struct drm_bridge *bridge,
> > > +                                        struct drm_bridge_state *old_bridge_state)
> > >  {
> > > -     struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode;
> > > -     struct sun6i_dsi *dsi = encoder_to_sun6i_dsi(encoder);
> > > +     struct sun6i_dsi *dsi = bridge_to_sun6i_dsi(bridge);
> > > +     struct drm_display_mode *mode = &bridge->encoder->crtc->state->adjusted_mode;
> > >       struct mipi_dsi_device *device = dsi->device;
> > >       union phy_configure_opts opts = { };
> > >       struct phy_configure_opts_mipi_dphy *cfg = &opts.mipi_dphy;
> > > @@ -772,6 +774,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> > >       if (dsi->panel)
> > >               drm_panel_prepare(dsi->panel);
> > >
> > > +     if (dsi->next_bridge)
> > > +             dsi->next_bridge->funcs->atomic_pre_enable(dsi->next_bridge, old_bridge_state);
> > > +
> >
> > Please use the proper helpers.
> 
> If we use bridge_functions we need to take atomic functions as
> precedence as the next bridge functions might convert atomic calls.

We've had this discussion over and over again, but this is something
that needs to be documented and / or in your commit log.

You must not deviate from the standard (and expected) behavior without
any kind of justification.

> >
> > >       /*
> > >        * FIXME: This should be moved after the switch to HS mode.
> > >        *
> > > @@ -787,6 +792,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> > >       if (dsi->panel)
> > >               drm_panel_enable(dsi->panel);
> > >
> > > +     if (dsi->next_bridge)
> > > +             dsi->next_bridge->funcs->atomic_enable(dsi->next_bridge, old_bridge_state);
> > > +
> >
> > Ditto
> >
> > >       sun6i_dsi_start(dsi, DSI_START_HSC);
> > >
> > >       udelay(1000);
> > > @@ -794,15 +802,19 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> > >       sun6i_dsi_start(dsi, DSI_START_HSD);
> > >  }
> > >
> > > -static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
> > > +static void sun6i_dsi_bridge_atomic_disable(struct drm_bridge *bridge,
> > > +                                         struct drm_bridge_state *old_bridge_state)
> > >  {
> > > -     struct sun6i_dsi *dsi = encoder_to_sun6i_dsi(encoder);
> > > +     struct sun6i_dsi *dsi = bridge_to_sun6i_dsi(bridge);
> > >
> > >       DRM_DEBUG_DRIVER("Disabling DSI output\n");
> > >
> > >       if (dsi->panel) {
> > >               drm_panel_disable(dsi->panel);
> > >               drm_panel_unprepare(dsi->panel);
> > > +     } else if (dsi->next_bridge) {
> > > +             dsi->next_bridge->funcs->atomic_disable(dsi->next_bridge, old_bridge_state);
> > > +             dsi->next_bridge->funcs->atomic_post_disable(dsi->next_bridge, old_bridge_state);
> >
> > Ditto
> >
> > >       }
> > >
> > >       phy_power_off(dsi->dphy);
> > > @@ -842,9 +854,25 @@ static const struct drm_connector_funcs sun6i_dsi_connector_funcs = {
> > >       .atomic_destroy_state   = drm_atomic_helper_connector_destroy_state,
> > >  };
> > >
> > > -static const struct drm_encoder_helper_funcs sun6i_dsi_enc_helper_funcs = {
> > > -     .disable        = sun6i_dsi_encoder_disable,
> > > -     .enable         = sun6i_dsi_encoder_enable,
> > > +static int sun6i_dsi_bridge_attach(struct drm_bridge *bridge,
> > > +                                enum drm_bridge_attach_flags flags)
> > > +{
> > > +     struct sun6i_dsi *dsi = bridge_to_sun6i_dsi(bridge);
> > > +
> > > +     if (dsi->next_bridge)
> > > +             return drm_bridge_attach(bridge->encoder, dsi->next_bridge,
> > > +                                      NULL, 0);
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +static const struct drm_bridge_funcs sun6i_dsi_bridge_funcs = {
> > > +     .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> > > +     .atomic_destroy_state   = drm_atomic_helper_bridge_destroy_state,
> > > +     .atomic_reset           = drm_atomic_helper_bridge_reset,
> > > +     .atomic_enable          = sun6i_dsi_bridge_atomic_enable,
> > > +     .atomic_disable         = sun6i_dsi_bridge_atomic_disable,
> > > +     .attach                 = sun6i_dsi_bridge_attach,
> > >  };
> > >
> > >  static u32 sun6i_dsi_dcs_build_pkt_hdr(struct sun6i_dsi *dsi,
> > > @@ -966,8 +994,6 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
> > >       struct sun6i_dsi *dsi = dev_get_drvdata(dev);
> > >       int ret;
> > >
> > > -     drm_encoder_helper_add(&dsi->encoder,
> > > -                            &sun6i_dsi_enc_helper_funcs);
> > >       ret = drm_simple_encoder_init(drm, &dsi->encoder,
> > >                                     DRM_MODE_ENCODER_DSI);
> > >       if (ret) {
> > > @@ -976,18 +1002,26 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
> > >       }
> > >       dsi->encoder.possible_crtcs = BIT(0);
> > >
> > > -     drm_connector_helper_add(&dsi->connector,
> > > -                              &sun6i_dsi_connector_helper_funcs);
> > > -     ret = drm_connector_init(drm, &dsi->connector,
> > > -                              &sun6i_dsi_connector_funcs,
> > > -                              DRM_MODE_CONNECTOR_DSI);
> > > +     ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL, 0);
> > >       if (ret) {
> > > -             dev_err(dsi->dev,
> > > -                     "Couldn't initialise the DSI connector\n");
> > > +             dev_err(dsi->dev, "Couldn't attach drm bridge\n");
> > >               goto err_cleanup_connector;
> > >       }
> > >
> > > -     drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> > > +     if (dsi->panel) {
> > > +             drm_connector_helper_add(&dsi->connector,
> > > +                                      &sun6i_dsi_connector_helper_funcs);
> > > +             ret = drm_connector_init(drm, &dsi->connector,
> > > +                                      &sun6i_dsi_connector_funcs,
> > > +                                      DRM_MODE_CONNECTOR_DSI);
> > > +             if (ret) {
> > > +                     dev_err(dsi->dev,
> > > +                             "Couldn't initialise the DSI connector\n");
> > > +                     goto err_cleanup_connector;
> > > +             }
> > > +
> > > +             drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> > > +     }
> > >
> > >       return 0;
> > >
> > > @@ -1013,16 +1047,46 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
> > >                           struct mipi_dsi_device *device)
> > >  {
> > >       struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
> > > -     struct drm_panel *panel = of_drm_find_panel(device->dev.of_node);
> > > +     struct device_node *remote = device->dev.of_node;
> > >       int ret;
> > >
> > > -     if (IS_ERR(panel))
> > > -             return PTR_ERR(panel);
> > > +     if (!of_device_is_available(remote)) {
> > > +             /**
> > > +              * I2C interfaced DSI bridges will register DSI host on the
> > > +              * bridge drivers instead of conventional device.
> > > +              *
> > > +              * Those are probed via host of_node instead of device of_node.
> > > +              */
> >
> > I have no idea what you mean here. Can you expand on what issue you've
> > tried to solve here?
> 
> I2C interface DSI bridges will register DSI host on the bridge
> drivers.

DSI bridges don't register a DSI host.

> Those can be found using host->dev->of_node and cannot be find using
> device->dev.of_node
> 
> >
> > > +             remote = of_graph_get_remote_node(host->dev->of_node, 0, 0);
> > > +             if (!remote)
> > > +                     return -ENODEV;
> > > +     }
> > > +
> > > +     dsi->panel = of_drm_find_panel(remote);
> > > +     if (IS_ERR(dsi->panel)) {
> > > +             dsi->panel = NULL;
> > > +
> > > +             dsi->next_bridge = of_drm_find_bridge(remote);
> > > +             if (IS_ERR(dsi->next_bridge)) {
> > > +                     dev_err(dsi->dev, "failed to find bridge\n");
> > > +                     return PTR_ERR(dsi->next_bridge);
> > > +             }
> > > +     } else {
> > > +             dsi->next_bridge = NULL;
> > > +     }
> > > +
> > > +     of_node_put(remote);
> >
> > Using devm_drm_of_get_bridge would greatly simplify the driver
> 
> I'm aware of this and this would break the existing sunxi dsi binding,
> we are not using ports based pipeline in dsi node. Of-course you have
> pointed the same before, please check below
> https://patchwork.kernel.org/project/dri-devel/patch/20210322140152.101709-2-jagan@amarulasolutions.com/

Then drm_of_find_panel_or_bridge needs to be adjusted to handle the DSI
bindings and look for a panel or bridge not only through the OF graph,
but also on the child nodes

Maxime