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

[Kalyan Thota]

>-----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);


>> +
>> +     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