Re: [PATCH 8/8] drm/bridge: it66121: Allow link this driver as a lib

[Sui Jingfeng]

Hi,

Thanks a lot for reviewing!


On 2023/11/15 00:30, Dmitry Baryshkov wrote:
> On Tue, 14 Nov 2023 at 17:09, Sui Jingfeng <sui.jingfeng@xxxxxxxxx> wrote:
> > From: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> >
> > The it66121_create_bridge() and it66121_destroy_bridge() are added to
> > export the core functionalities. Create a connector manually by using
> > bridge connector helpers when link as a lib.
> >
> > Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/bridge/ite-it66121.c | 134 +++++++++++++++++++--------
> >   include/drm/bridge/ite-it66121.h     |  17 ++++
> >   2 files changed, 113 insertions(+), 38 deletions(-)
> >   create mode 100644 include/drm/bridge/ite-it66121.h
> >
> > diff --git a/drivers/gpu/drm/bridge/ite-it66121.c b/drivers/gpu/drm/bridge/ite-it66121.c
> > index 8971414a2a60..f5968b679c5d 100644
> > --- a/drivers/gpu/drm/bridge/ite-it66121.c
> > +++ b/drivers/gpu/drm/bridge/ite-it66121.c
> > @@ -22,6 +22,7 @@
> >
> >   #include <drm/drm_atomic_helper.h>
> >   #include <drm/drm_bridge.h>
> > +#include <drm/drm_bridge_connector.h>
> >   #include <drm/drm_edid.h>
> >   #include <drm/drm_modes.h>
> >   #include <drm/drm_print.h>
> > @@ -703,14 +704,32 @@ static int it66121_bridge_attach(struct drm_bridge *bridge,
> >                                   enum drm_bridge_attach_flags flags)
> >   {
> >          struct it66121_ctx *ctx = bridge_to_it66121(bridge);
> > +       struct drm_bridge *next_bridge = ctx->next_bridge;
> > +       struct drm_encoder *encoder = bridge->encoder;
> >          int ret;
> >
> > -       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> > -               return -EINVAL;
> > +       if (next_bridge) {
> > +               if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
> > +                       WARN_ON(1);
> Why? At least use WARN() instead

Originally I want to




> > +                       flags |= DRM_BRIDGE_ATTACH_NO_CONNECTOR;
> > +               }
> > +               ret = drm_bridge_attach(encoder, next_bridge, bridge, flags);
> > +               if (ret)
> > +                       return ret;
> > +       } else {
> > +               struct drm_connector *connector;
> >
> > -       ret = drm_bridge_attach(bridge->encoder, ctx->next_bridge, bridge, flags);
> > -       if (ret)
> > -               return ret;
> > +               if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
> > +                       WARN_ON(1);
> No. It is perfectly fine to create attach a bridge with no next_bridge
> and with the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.

The document say when DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is set
the bridge shall not create a drm_connector. So I think if a display
bridge driver don't have a next bridge attached (Currently, this is
told by the DT), it says that this is a non-DT environment. On such
a case, this display bridge driver(it66121.ko) should behavior like
a *agent*. Because the upstream port of it66121 is the DVO port of
the display controller, the downstream port of it66121 is the HDMI
connector. it66121 is on the middle. So I think the it66121.ko should
handle all of troubles on behalf of the display controller drivers.

Therefore (when in non-DT use case), the display controller drivers
side should not set DRM_BRIDGE_ATTACH_NO_CONNECTOR flag anymore.
Which is to hint that the it66121 should totally in charge of those
tasks (either by using bridge connector helper or create a connector
manually). I don't understand on such a case, why bother display
controller drivers anymore.


> > +
> > +               connector = drm_bridge_connector_init(bridge->dev, encoder);
> > +               if (IS_ERR(connector))
> > +                       return PTR_ERR(connector);
> > +
> > +               drm_connector_attach_encoder(connector, encoder);
> This goes into your device driver.
>
> > +
> > +               ctx->connector = connector;
> > +       }
> >
> >          if (ctx->info->id == ID_IT66121) {
> >                  ret = regmap_write_bits(ctx->regmap, IT66121_CLK_BANK_REG,
> > @@ -1632,16 +1651,13 @@ static const char * const it66121_supplies[] = {
> >          "vcn33", "vcn18", "vrf12"
> >   };