Re: [PATCH v3 2/3] drm/msm/disp/dpu1: add helper to know if display is builtin

[Dmitry Baryshkov]

On 18/11/2022 16:37, Kalyan Thota wrote:
> > -----Original Message-----
> > From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > Sent: Friday, November 18, 2022 6:09 PM
> > To: Kalyan Thota (QUIC) <quic_kalyant@xxxxxxxxxxx>; dri-
> > devel@xxxxxxxxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx;
> > freedreno@xxxxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx; robdclark@xxxxxxxxxxxx;
> > dianders@xxxxxxxxxxxx; swboyd@xxxxxxxxxxxx; Vinod Polimera (QUIC)
> > <quic_vpolimer@xxxxxxxxxxx>; Abhinav Kumar (QUIC)
> > <quic_abhinavk@xxxxxxxxxxx>
> > Subject: Re: [PATCH v3 2/3] drm/msm/disp/dpu1: add helper to know if display is
> > builtin
> >
> > WARNING: This email originated from outside of Qualcomm. Please be wary of
> > any links or attachments, and do not enable macros.
> >
> > On 18/11/2022 15:16, Kalyan Thota wrote:
> > > Since DRM encoder type for few encoders can be similar (like eDP and
> > > DP) find out if the interface supports HPD from encoder bridge to
> > > differentiate between builtin and pluggable displays.
> > >
> > > Changes in v1:
> > > - add connector type in the disp_info (Dmitry)
> > > - add helper functions to know encoder type
> > > - update commit text reflecting the change
> > >
> > > Changes in v2:
> > > - avoid hardcode of connector type for DSI as it may not be true
> > > (Dmitry)
> > > - get the HPD information from encoder bridge
> > >
> > > Changes in v3:
> > > - use bridge type instead of bridge ops in determining connector
> > > (Dmitry)
> > >
> > > Signed-off-by: Kalyan Thota <quic_kalyant@xxxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 27
> > +++++++++++++++++++++++++++
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h |  6 ++++++
> > >    2 files changed, 33 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > index 9c6817b..574f2b0 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > @@ -15,6 +15,7 @@
> > >    #include <drm/drm_crtc.h>
> > >    #include <drm/drm_file.h>
> > >    #include <drm/drm_probe_helper.h>
> > > +#include <drm/drm_bridge.h>
> > >
> > >    #include "msm_drv.h"
> > >    #include "dpu_kms.h"
> > > @@ -217,6 +218,32 @@ static u32 dither_matrix[DITHER_MATRIX_SZ] = {
> > >        15, 7, 13, 5, 3, 11, 1, 9, 12, 4, 14, 6, 0, 8, 2, 10
> > >    };
> > >
> > > +bool dpu_encoder_is_builtin(struct drm_encoder *encoder) {
> > > +     struct drm_bridge *bridge;
> > > +     int ops = 0;
> > > +
> > > +     if (!encoder)
> > > +             return false;
> > > +
> > > +     /* Get last bridge in the chain to determine connector type */
> > > +     drm_for_each_bridge_in_chain(encoder, bridge)
> > > +             if (!drm_bridge_get_next_bridge(bridge))
> > > +                     ops = bridge->type;
> >
> > Why don't we check the connector type directly? You should not assume that
> > connector's type is equal to the latest bridge's type.
>
> if we need to get the type from connector, need to do something as below.
> Are you thinking on the same lines ?
>
> "to_drm_bridge_connector" macro needs to be moved to drm_bridge_connector.h
>
> struct drm_bridge_connector *bridge_connector;
>
> drm_connector_list_iter_begin(dev, &conn_iter);
> 	drm_for_each_connector_iter(connector, &conn_iter) {
>
> 		bridge_connector = to_drm_bridge_connector(connector);
> 		if (bridge_connector->encoder == encoder) {
> 			type = connector->connector_type;
> 			break;
> 		}
> 	}
> drm_connector_list_iter_end(&conn_iter);

No. You can not depend on the idea that every connector is 
drm_bridge_connector. Some bridges might create their own connectors. 
However you can do it in the following way:

drm_connector_list_iter_begin(dev, &iter);
drm_for_each_connector_iter(connector, &iter) {
 if (connector->possible_encoders & drm_encoder_mask(encoder)) {
    builtin = (connector->connector_type == DRM_MODE_CONNECTOR_LVDS) || 
...;
    break;
  }
}
drm_connector_list_iter_end(&iter);

return builtin;


> > > +
> > > +     switch (ops) {
> > > +     case DRM_MODE_CONNECTOR_Unknown:
> > > +     case DRM_MODE_CONNECTOR_LVDS:
> > > +     case DRM_MODE_CONNECTOR_eDP:
> > > +     case DRM_MODE_CONNECTOR_DSI:
> > > +     case DRM_MODE_CONNECTOR_DPI:
> > > +     case DRM_MODE_CONNECTOR_WRITEBACK:
> > > +     case DRM_MODE_CONNECTOR_VIRTUAL:
> >
> > Unknown, WRITEBACK and VIRTUAL are not builtin (for the point of CTM at
> > least).
> >
> > > +             return true;
> > > +     default:
> > > +             return false;
> > > +     }
> > > +}
> > >
> > >    bool dpu_encoder_is_widebus_enabled(const struct drm_encoder *drm_enc)
> > >    {
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> > > index 9e7236e..7f3d823 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> > > @@ -224,4 +224,10 @@ void dpu_encoder_cleanup_wb_job(struct
> > drm_encoder *drm_enc,
> > >     */
> > >    bool dpu_encoder_is_valid_for_commit(struct drm_encoder *drm_enc);
> > >
> > > +/**
> > > + * dpu_encoder_is_builtin - find if the encoder is of type builtin
> > > + * @drm_enc:    Pointer to previously created drm encoder structure
> > > + */
> > > +bool dpu_encoder_is_builtin(struct drm_encoder *drm_enc);
> > > +
> > >    #endif /* __DPU_ENCODER_H__ */
> >
> > --
> > With best wishes
> > Dmitry

--
With best wishes
Dmitry