Date:   Sat, 6 Nov 2021 11:25:41 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, dmitry.baryshkov@...aro.org,
        quic_abhinavk@...cinc.com, aravindh@...eaurora.org,
        freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dp:  employ bridge mechanism for display
 enable and disable

On Fri 05 Nov 16:22 CDT 2021, Kuogee Hsieh wrote:

> Currently the msm_dp_*** functions implement the same sequence which would
> happen when drm_bridge is used. hence get rid of this intermediate layer
> and align with the drm_bridge usage to avoid customized implementation.
> 
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> 
> Changes in v2:
> -- revise commit text
> -- rename dp_bridge to msm_dp_bridge
> -- delete empty functions
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 21 -------
>  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c     |  7 +++
>  drivers/gpu/drm/msm/dp/dp_display.c         | 18 +++---
>  drivers/gpu/drm/msm/dp/dp_display.h         |  1 +
>  drivers/gpu/drm/msm/dp/dp_drm.c             | 91 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/msm_drv.h               | 16 +++--
>  6 files changed, 120 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 31050aa..c4e08c4 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -1003,9 +1003,6 @@ static void dpu_encoder_virt_mode_set(struct drm_encoder *drm_enc,
>  
>  	trace_dpu_enc_mode_set(DRMID(drm_enc));
>  
> -	if (drm_enc->encoder_type == DRM_MODE_ENCODER_TMDS)
> -		msm_dp_display_mode_set(dpu_enc->dp, drm_enc, mode, adj_mode);
> -
>  	list_for_each_entry(conn_iter, connector_list, head)
>  		if (conn_iter->encoder == drm_enc)
>  			conn = conn_iter;
> @@ -1181,14 +1178,6 @@ static void dpu_encoder_virt_enable(struct drm_encoder *drm_enc)
>  
>  	_dpu_encoder_virt_enable_helper(drm_enc);
>  
> -	if (drm_enc->encoder_type == DRM_MODE_ENCODER_TMDS) {
> -		ret = msm_dp_display_enable(dpu_enc->dp, drm_enc);
> -		if (ret) {
> -			DPU_ERROR_ENC(dpu_enc, "dp display enable failed: %d\n",
> -				ret);
> -			goto out;
> -		}
> -	}
>  	dpu_enc->enabled = true;
>  
>  out:
> @@ -1214,11 +1203,6 @@ static void dpu_encoder_virt_disable(struct drm_encoder *drm_enc)
>  	/* wait for idle */
>  	dpu_encoder_wait_for_event(drm_enc, MSM_ENC_TX_COMPLETE);
>  
> -	if (drm_enc->encoder_type == DRM_MODE_ENCODER_TMDS) {
> -		if (msm_dp_display_pre_disable(dpu_enc->dp, drm_enc))
> -			DPU_ERROR_ENC(dpu_enc, "dp display push idle failed\n");
> -	}
> -
>  	dpu_encoder_resource_control(drm_enc, DPU_ENC_RC_EVENT_PRE_STOP);
>  
>  	for (i = 0; i < dpu_enc->num_phys_encs; i++) {
> @@ -1243,11 +1227,6 @@ static void dpu_encoder_virt_disable(struct drm_encoder *drm_enc)
>  
>  	DPU_DEBUG_ENC(dpu_enc, "encoder disabled\n");
>  
> -	if (drm_enc->encoder_type == DRM_MODE_ENCODER_TMDS) {
> -		if (msm_dp_display_disable(dpu_enc->dp, drm_enc))
> -			DPU_ERROR_ENC(dpu_enc, "dp display disable failed\n");
> -	}
> -
>  	mutex_unlock(&dpu_enc->enc_lock);
>  }
>  
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index 27d98b5..d16337f 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -557,6 +557,13 @@ static int _dpu_kms_initialize_displayport(struct drm_device *dev,
>  				  encoder->base.id, rc);
>  			return rc;
>  		}
> +
> +		rc = msm_dp_bridge_init(priv->dp[i], dev, encoder);
> +		if (rc) {
> +			DPU_ERROR("failed to setup DPU bridge %d: rc:%d\n",
> +				encoder->base.id, rc);
> +			return rc;
> +		}
>  	}
>  
>  	return rc;
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index e41dd40..e9ea6ed 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -569,8 +569,8 @@ static int dp_hpd_plug_handle(struct dp_display_private *dp, u32 data)
>  	return 0;
>  };
>  
> -static int dp_display_enable(struct dp_display_private *dp, u32 data);
> -static int dp_display_disable(struct dp_display_private *dp, u32 data);
> +static int __dp_display_enable(struct dp_display_private *dp, u32 data);
> +static int __dp_display_disable(struct dp_display_private *dp, u32 data);

Can you please help me understand why you're changing the name of these
functions?

>  
>  static int dp_connect_pending_timeout(struct dp_display_private *dp, u32 data)
>  {
> @@ -855,7 +855,7 @@ static int dp_display_prepare(struct msm_dp *dp_display)
>  	return 0;
>  }
>  
> -static int dp_display_enable(struct dp_display_private *dp, u32 data)
> +static int __dp_display_enable(struct dp_display_private *dp, u32 data)
>  {
>  	int rc = 0;
>  
> @@ -898,7 +898,7 @@ static int dp_display_post_enable(struct msm_dp *dp_display)
>  	return 0;
>  }
>  
> -static int dp_display_disable(struct dp_display_private *dp, u32 data)
> +static int __dp_display_disable(struct dp_display_private *dp, u32 data)
>  {
>  	struct msm_dp *dp_display = &dp->dp_display;
>  
> @@ -1569,12 +1569,12 @@ int msm_dp_display_enable(struct msm_dp *dp, struct drm_encoder *encoder)
>  	if (state == ST_DISPLAY_OFF)
>  		dp_display_host_init(dp_display, true);
>  
> -	dp_display_enable(dp_display, 0);
> +	__dp_display_enable(dp_display, 0);
>  
>  	rc = dp_display_post_enable(dp);
>  	if (rc) {
>  		DRM_ERROR("DP display post enable failed, rc=%d\n", rc);
> -		dp_display_disable(dp_display, 0);
> +		__dp_display_disable(dp_display, 0);
>  		dp_display_unprepare(dp);
>  	}
>  
> @@ -1614,7 +1614,7 @@ int msm_dp_display_disable(struct msm_dp *dp, struct drm_encoder *encoder)
>  	/* stop sentinel checking */
>  	dp_del_event(dp_display, EV_DISCONNECT_PENDING_TIMEOUT);
>  
> -	dp_display_disable(dp_display, 0);
> +	__dp_display_disable(dp_display, 0);
>  
>  	rc = dp_display_unprepare(dp);
>  	if (rc)
> @@ -1633,8 +1633,8 @@ int msm_dp_display_disable(struct msm_dp *dp, struct drm_encoder *encoder)
>  }
>  
>  void msm_dp_display_mode_set(struct msm_dp *dp, struct drm_encoder *encoder,
> -				struct drm_display_mode *mode,
> -				struct drm_display_mode *adjusted_mode)
> +				const struct drm_display_mode *mode,
> +				const struct drm_display_mode *adjusted_mode)
>  {
>  	struct dp_display_private *dp_display;
>  
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index 76f45f9..2237e80 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -13,6 +13,7 @@
>  struct msm_dp {
>  	struct drm_device *drm_dev;
>  	struct device *codec_dev;
> +	struct drm_bridge *bridge;
>  	struct drm_connector *connector;
>  	struct drm_encoder *encoder;
>  	struct drm_panel *drm_panel;
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index f33e315..e7bea97 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -5,12 +5,21 @@
>  
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_atomic.h>
> +#include <drm/drm_bridge.h>
>  #include <drm/drm_crtc.h>
>  
>  #include "msm_drv.h"
>  #include "msm_kms.h"
>  #include "dp_drm.h"
>  
> +
> +struct msm_dp_bridge {
> +	struct drm_bridge bridge;
> +	struct msm_dp *dp_display;
> +};

We do you create yet another one of these object?

Can't we just set up the new bridge in msm_dp_modeset_init(), like is
done in msm_dsi_modeset_init()?

> +
> +#define to_dp_display(x)     container_of((x), struct msm_dp_bridge, bridge)
> +
>  struct dp_connector {
>  	struct drm_connector base;
>  	struct msm_dp *dp_display;
> @@ -162,3 +171,85 @@ struct drm_connector *dp_drm_connector_init(struct msm_dp *dp_display)
>  
>  	return connector;
>  }
> +
> +static int dp_bridge_attach(struct drm_bridge *drm_bridge,
> +				enum drm_bridge_attach_flags flags)
> +{
> +	return 0;
> +}
> +
> +static void dp_bridge_mode_set(struct drm_bridge *drm_bridge,
> +				const struct drm_display_mode *mode,
> +				const struct drm_display_mode *adjusted_mode)
> +{
> +	struct msm_dp_bridge *dp_bridge = to_dp_display(drm_bridge);
> +	struct msm_dp *dp_display = dp_bridge->dp_display;
> +
> +	msm_dp_display_mode_set(dp_display, drm_bridge->encoder, mode, adjusted_mode);
> +}
> +
> +static void dp_bridge_enable(struct drm_bridge *drm_bridge)
> +{
> +	struct msm_dp_bridge *dp_bridge = to_dp_display(drm_bridge);
> +	struct msm_dp *dp_display = dp_bridge->dp_display;
> +
> +	msm_dp_display_enable(dp_display, drm_bridge->encoder);
> +}
> +
> +static void dp_bridge_disable(struct drm_bridge *drm_bridge)
> +{
> +	struct msm_dp_bridge *dp_bridge = to_dp_display(drm_bridge);
> +	struct msm_dp *dp_display = dp_bridge->dp_display;
> +
> +	msm_dp_display_pre_disable(dp_display, drm_bridge->encoder);
> +}
> +
> +static void dp_bridge_post_disable(struct drm_bridge *drm_bridge)
> +{
> +	struct msm_dp_bridge *dp_bridge = to_dp_display(drm_bridge);
> +	struct msm_dp *dp_display = dp_bridge->dp_display;
> +
> +	msm_dp_display_disable(dp_display, drm_bridge->encoder);
> +}
> +
> +static const struct drm_bridge_funcs dp_bridge_ops = {
> +	.attach       = dp_bridge_attach,
> +	.mode_fixup   = NULL,
> +	.pre_enable   = NULL,
> +	.enable       = dp_bridge_enable,
> +	.disable      = dp_bridge_disable,
> +	.post_disable = dp_bridge_post_disable,
> +	.mode_set     = dp_bridge_mode_set,
> +};
> +
> +int msm_dp_bridge_init(struct msm_dp *dp_display, struct drm_device *dev,
> +			struct drm_encoder *encoder)
> +{
> +	int rc;
> +	struct msm_drm_private *priv;
> +	struct msm_dp_bridge *dp_bridge;
> +	struct drm_bridge *bridge;
> +
> +	dp_bridge = kzalloc(sizeof(*dp_bridge), GFP_KERNEL);

You're not freeing this pointer, except for the error case below. That
said, you call this from dpu_kms_hw_init() which is full of other things
relying on devres.

So I think the appropriate way here is to use devm_kzalloc().

> +	if (!dp_bridge)
> +		return -ENOMEM;
> +
> +	dp_bridge->dp_display = dp_display;
> +
> +	bridge = &dp_bridge->bridge;
> +	bridge->funcs = &dp_bridge_ops;
> +	bridge->encoder = encoder;
> +
> +	rc = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);

Sorry, my understanding of the drm_bridge is limited, but how does this
interact with the panel_bridge that we attach in
dp_drm_connector_init()?

If we represent the DP instance itself as a drm_bridge, shouldn't that
be "previous" of the panel_bridge?

> +	if (rc) {
> +		DRM_ERROR("failed to attach bridge, rc=%d\n", rc);
> +		kfree(dp_bridge);
> +		return rc;
> +	}
> +
> +	priv = dev->dev_private;
> +	priv->bridges[priv->num_bridges++] = bridge;
> +	dp_display->bridge = bridge;
> +
> +	return 0;
> +}
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 4bb797e..9a2092f 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -388,8 +388,10 @@ int msm_dp_display_enable(struct msm_dp *dp, struct drm_encoder *encoder);
>  int msm_dp_display_disable(struct msm_dp *dp, struct drm_encoder *encoder);
>  int msm_dp_display_pre_disable(struct msm_dp *dp, struct drm_encoder *encoder);
>  void msm_dp_display_mode_set(struct msm_dp *dp, struct drm_encoder *encoder,
> -				struct drm_display_mode *mode,
> -				struct drm_display_mode *adjusted_mode);
> +				const struct drm_display_mode *mode,
> +				const struct drm_display_mode *adjusted_mode);
> +int msm_dp_bridge_init(struct msm_dp *dp_display, struct drm_device *dev,
> +			struct drm_encoder *encoder);
>  void msm_dp_irq_postinstall(struct msm_dp *dp_display);
>  void msm_dp_snapshot(struct msm_disp_state *disp_state, struct msm_dp *dp_display);
>  
> @@ -426,10 +428,16 @@ static inline int msm_dp_display_pre_disable(struct msm_dp *dp,
>  }
>  static inline void msm_dp_display_mode_set(struct msm_dp *dp,
>  				struct drm_encoder *encoder,
> -				struct drm_display_mode *mode,
> -				struct drm_display_mode *adjusted_mode)
> +				const struct drm_display_mode *mode,
> +				const struct drm_display_mode *adjusted_mode)
>  {
>  }
> +static inline int msm_dp_bridge_init(struct msm_dp *dp_display,
> +				struct drm_device *dev,
> +				struct drm_encoder *encoder)
> +{
> +	return -EINVAL;

Returning an error here means that building without CONFIG_DRM_MSM_DP
we will propagate an error up and fail the entire DPU initialization.

Perhaps this problem already exists today?

Regards,
Bjorn

> +}
>  
>  static inline void msm_dp_irq_postinstall(struct msm_dp *dp_display)
>  {
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 

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