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

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Message-ID: <5dddeaa9-aab1-e437-a3ed-8ad242d50171@linaro.org>
Date:   Fri, 18 Nov 2022 14:38:37 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     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, quic_abhinavk@...cinc.com
Subject: Re: [PATCH v3 2/3] drm/msm/disp/dpu1: add helper to know if display
 is builtin

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@...cinc.com>
> ---
>   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.

> +
> +	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