Date:   Fri, 6 May 2022 23:49:15 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Cc:     robdclark@...il.com, seanpaul@...omium.org, swboyd@...omium.org,
        quic_kalyant@...cinc.com, quic_abhinavk@...cinc.com,
        dianders@...omium.org, quic_khsieh@...cinc.com,
        bjorn.andersson@...aro.org, sean@...rly.run, airlied@...ux.ie,
        daniel@...ll.ch, quic_vproddut@...cinc.com,
        quic_aravindh@...cinc.com, steev@...i.org
Subject: Re: [PATCH v10 1/4] drm/msm/dp: Add eDP support via aux_bus

On 25/04/2022 14:44, Sankeerth Billakanti wrote:
> This patch adds support for generic eDP sink through aux_bus. The eDP/DP
> controller driver should support aux transactions originating from the
> panel-edp driver and hence should be initialized and ready.
> 
> The panel bridge supporting the panel should be ready before the bridge
> connector is initialized. The generic panel probe needs the controller
> resources to be enabled to support the aux transactions originating from
> the panel probe.
> 
> Signed-off-by: Sankeerth Billakanti <quic_sbillaka@...cinc.com>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>

An additional side effect from this patch. Previously missing panel 
would have caused the bind error. Now it is the dp_modeset_init error, 
which translates to kms_hw_init returning -517. I kind ask to move the 
next_bridge acquisition back to the dp_bind in one of the followup patches.

> ---
> Changes in v10:
>    - modify the error handling condition
>    - modify the kernel doc
> 
> Changes in v9:
>    - add comments for panel probe
>    - modify the error handling checks
> 
> Changes in v8:
>    - handle corner cases
>    - add comment for the bridge ops
> 
> Changes in v7:
>    - aux_bus is mandatory for eDP
>    - connector type check modified to just check for eDP
> 
> Changes in v6:
>    - Remove initialization
>    - Fix aux_bus node leak
>    - Split the patches
> 
>   drivers/gpu/drm/msm/dp/dp_display.c | 72 ++++++++++++++++++++++++++++++++++---
>   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>   drivers/gpu/drm/msm/dp/dp_drm.c     | 21 ++++++++---
>   drivers/gpu/drm/msm/dp/dp_parser.c  | 23 ++----------
>   drivers/gpu/drm/msm/dp/dp_parser.h  | 14 +++++++-
>   5 files changed, 101 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index d7a19d6..f772d84 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -10,6 +10,7 @@
>   #include <linux/component.h>
>   #include <linux/of_irq.h>
>   #include <linux/delay.h>
> +#include <drm/dp/drm_dp_aux_bus.h>
>   
>   #include "msm_drv.h"
>   #include "msm_kms.h"
> @@ -259,14 +260,12 @@ static int dp_display_bind(struct device *dev, struct device *master,
>   	dp->dp_display.drm_dev = drm;
>   	priv->dp[dp->id] = &dp->dp_display;
>   
> -	rc = dp->parser->parse(dp->parser, dp->dp_display.connector_type);
> +	rc = dp->parser->parse(dp->parser);
>   	if (rc) {
>   		DRM_ERROR("device tree parsing failed\n");
>   		goto end;
>   	}
>   
> -	dp->dp_display.next_bridge = dp->parser->next_bridge;
> -
>   	dp->aux->drm_dev = drm;
>   	rc = dp_aux_register(dp->aux);
>   	if (rc) {
> @@ -1319,6 +1318,8 @@ static int dp_display_probe(struct platform_device *pdev)
>   	dp->pdev = pdev;
>   	dp->name = "drm_dp";
>   	dp->dp_display.connector_type = desc->connector_type;
> +	dp->dp_display.is_edp =
> +		(dp->dp_display.connector_type == DRM_MODE_CONNECTOR_eDP);
>   
>   	rc = dp_init_sub_modules(dp);
>   	if (rc) {
> @@ -1508,7 +1509,8 @@ void msm_dp_irq_postinstall(struct msm_dp *dp_display)
>   
>   	dp_hpd_event_setup(dp);
>   
> -	dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
> +	if (!dp_display->is_edp)
> +		dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
>   }
>   
>   void msm_dp_debugfs_init(struct msm_dp *dp_display, struct drm_minor *minor)
> @@ -1530,6 +1532,64 @@ void msm_dp_debugfs_init(struct msm_dp *dp_display, struct drm_minor *minor)
>   	}
>   }
>   
> +static int dp_display_get_next_bridge(struct msm_dp *dp)
> +{
> +	int rc;
> +	struct dp_display_private *dp_priv;
> +	struct device_node *aux_bus;
> +	struct device *dev;
> +
> +	dp_priv = container_of(dp, struct dp_display_private, dp_display);
> +	dev = &dp_priv->pdev->dev;
> +	aux_bus = of_get_child_by_name(dev->of_node, "aux-bus");
> +
> +	if (aux_bus && dp->is_edp) {
> +		dp_display_host_init(dp_priv);
> +		dp_catalog_ctrl_hpd_config(dp_priv->catalog);
> +		dp_display_host_phy_init(dp_priv);
> +		enable_irq(dp_priv->irq);
> +
> +		/*
> +		 * The code below assumes that the panel will finish probing
> +		 * by the time devm_of_dp_aux_populate_ep_devices() returns.
> +		 * This isn't a great assumption since it will fail if the
> +		 * panel driver is probed asynchronously but is the best we
> +		 * can do without a bigger driver reorganization.
> +		 */
> +		rc = devm_of_dp_aux_populate_ep_devices(dp_priv->aux);
> +		of_node_put(aux_bus);
> +		if (rc)
> +			goto error;
> +	} else if (dp->is_edp) {
> +		DRM_ERROR("eDP aux_bus not found\n");
> +		return -ENODEV;
> +	}
> +
> +	/*
> +	 * External bridges are mandatory for eDP interfaces: one has to
> +	 * provide at least an eDP panel (which gets wrapped into panel-bridge).
> +	 *
> +	 * For DisplayPort interfaces external bridges are optional, so
> +	 * silently ignore an error if one is not present (-ENODEV).
> +	 */
> +	rc = dp_parser_find_next_bridge(dp_priv->parser);
> +	if (!dp->is_edp && rc == -ENODEV)
> +		return 0;
> +
> +	if (!rc) {
> +		dp->next_bridge = dp_priv->parser->next_bridge;
> +		return 0;
> +	}
> +
> +error:
> +	if (dp->is_edp) {
> +		disable_irq(dp_priv->irq);
> +		dp_display_host_phy_exit(dp_priv);
> +		dp_display_host_deinit(dp_priv);
> +	}
> +	return rc;
> +}
> +
>   int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>   			struct drm_encoder *encoder)
>   {
> @@ -1553,6 +1613,10 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, struct drm_device *dev,
>   
>   	dp_display->encoder = encoder;
>   
> +	ret = dp_display_get_next_bridge(dp_display);
> +	if (ret)
> +		return ret;
> +
>   	dp_display->bridge = dp_bridge_init(dp_display, dev, encoder);
>   	if (IS_ERR(dp_display->bridge)) {
>   		ret = PTR_ERR(dp_display->bridge);
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index 49a1d89..1377cc3 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -21,6 +21,7 @@ struct msm_dp {
>   	bool audio_enabled;
>   	bool power_on;
>   	unsigned int connector_type;
> +	bool is_edp;
>   
>   	hdmi_codec_plugged_cb plugged_cb;
>   
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index 7ce1aca..8a75c55 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -114,10 +114,23 @@ struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct drm_device *
>   	bridge->funcs = &dp_bridge_ops;
>   	bridge->type = dp_display->connector_type;
>   
> -	bridge->ops =
> -		DRM_BRIDGE_OP_DETECT |
> -		DRM_BRIDGE_OP_HPD |
> -		DRM_BRIDGE_OP_MODES;
> +	/*
> +	 * Many ops only make sense for DP. Why?
> +	 * - Detect/HPD are used by DRM to know if a display is _physically_
> +	 *   there, not whether the display is powered on / finished initting.
> +	 *   On eDP we assume the display is always there because you can't
> +	 *   know until power is applied. If we don't implement the ops DRM will
> +	 *   assume our display is always there.
> +	 * - Currently eDP mode reading is driven by the panel driver. This
> +	 *   allows the panel driver to properly power itself on to read the
> +	 *   modes.
> +	 */
> +	if (!dp_display->is_edp) {
> +		bridge->ops =
> +			DRM_BRIDGE_OP_DETECT |
> +			DRM_BRIDGE_OP_HPD |
> +			DRM_BRIDGE_OP_MODES;
> +	}
>   
>   	rc = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>   	if (rc) {
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
> index 1056b8d..4bdbf91 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -265,7 +265,7 @@ static int dp_parser_clock(struct dp_parser *parser)
>   	return 0;
>   }
>   
> -static int dp_parser_find_next_bridge(struct dp_parser *parser)
> +int dp_parser_find_next_bridge(struct dp_parser *parser)
>   {
>   	struct device *dev = &parser->pdev->dev;
>   	struct drm_bridge *bridge;
> @@ -279,7 +279,7 @@ static int dp_parser_find_next_bridge(struct dp_parser *parser)
>   	return 0;
>   }
>   
> -static int dp_parser_parse(struct dp_parser *parser, int connector_type)
> +static int dp_parser_parse(struct dp_parser *parser)
>   {
>   	int rc = 0;
>   
> @@ -300,25 +300,6 @@ static int dp_parser_parse(struct dp_parser *parser, int connector_type)
>   	if (rc)
>   		return rc;
>   
> -	/*
> -	 * External bridges are mandatory for eDP interfaces: one has to
> -	 * provide at least an eDP panel (which gets wrapped into panel-bridge).
> -	 *
> -	 * For DisplayPort interfaces external bridges are optional, so
> -	 * silently ignore an error if one is not present (-ENODEV).
> -	 */
> -	rc = dp_parser_find_next_bridge(parser);
> -	if (rc == -ENODEV) {
> -		if (connector_type == DRM_MODE_CONNECTOR_eDP) {
> -			DRM_ERROR("eDP: next bridge is not present\n");
> -			return rc;
> -		}
> -	} else if (rc) {
> -		if (rc != -EPROBE_DEFER)
> -			DRM_ERROR("DP: error parsing next bridge: %d\n", rc);
> -		return rc;
> -	}
> -
>   	/* Map the corresponding regulator information according to
>   	 * version. Currently, since we only have one supported platform,
>   	 * mapping the regulator directly.
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
> index d371bae..3a4d797 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.h
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.h
> @@ -125,7 +125,7 @@ struct dp_parser {
>   	u32 max_dp_lanes;
>   	struct drm_bridge *next_bridge;
>   
> -	int (*parse)(struct dp_parser *parser, int connector_type);
> +	int (*parse)(struct dp_parser *parser);
>   };
>   
>   /**
> @@ -141,4 +141,16 @@ struct dp_parser {
>    */
>   struct dp_parser *dp_parser_get(struct platform_device *pdev);
>   
> +/**
> + * dp_parser_find_next_bridge() - find an additional bridge to DP
> + *
> + * @parser: dp_parser data from client
> + *
> + * This function is used to find any additional bridge attached to
> + * the DP controller. The eDP interface requires a panel bridge.
> + *
> + * Return: 0 if able to get the bridge, otherwise negative errno for failure.
> + */
> +int dp_parser_find_next_bridge(struct dp_parser *parser);
> +
>   #endif


-- 
With best wishes
Dmitry

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