linux-kernel - Re: [PATCH v2 2/3] drm/msm/disp/dpu1: add helper to know if display is pluggable

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Message-ID: <6b1907db-3fdb-8fe0-e5e3-21ea17021925@quicinc.com>
Date:   Wed, 16 Nov 2022 07:11:16 -0800
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Kalyan Thota <quic_kalyant@...cinc.com>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <freedreno@...ts.freedesktop.org>, <devicetree@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <robdclark@...omium.org>,
        <dianders@...omium.org>, <swboyd@...omium.org>,
        <quic_vpolimer@...cinc.com>
Subject: Re: [PATCH v2 2/3] drm/msm/disp/dpu1: add helper to know if display
 is pluggable



On 11/16/2022 7:08 AM, Dmitry Baryshkov wrote:
> On 16/11/2022 17:30, 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
>>
>> Signed-off-by: Kalyan Thota <quic_kalyant@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 16 ++++++++++++++++
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h |  6 ++++++
>>   2 files changed, 22 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..be93269 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 +218,21 @@ 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_pluggable(struct drm_encoder *encoder)
>> +{
>> +    struct drm_bridge *bridge;
>> +    int ops = 0;
>> +
>> +    if (!encoder)
>> +        return false;
>> +
>> +    /* Get last bridge in the chain to determine pluggable state */
>> +    drm_for_each_bridge_in_chain(encoder, bridge)
>> +        if (!drm_bridge_get_next_bridge(bridge))
>> +            ops = bridge->ops;
>> +
>> +    return ops & DRM_BRIDGE_OP_HPD;
> 
> No. This is not what you should be checking (hint: polled connectors 
> also can be pluggable).
> 
> Please check the type of the actual connector connected to this encoder.
> 

Even if we check the connector type as DSI or eDP that does not 
necessarily mean its built-in.

We can even use DSI or eDP as a pluggable display.

Thats why we thought of this check.

>> +}
>>   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..691ab57 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_pluggable - find if the encoder is of type pluggable
>> + * @drm_enc:    Pointer to previously created drm encoder structure
>> + */
>> +bool dpu_encoder_is_pluggable(struct drm_encoder *drm_enc);
>> +
>>   #endif /* __DPU_ENCODER_H__ */
>