Re: [Freedreno] [PATCH v4 4/7] drm/msm/dp: Allow attaching a drm_panel

[abhinavk@codeaurora.org]

Hi Bjorn

On 2021-10-05 16:13, Bjorn Andersson wrote:
> eDP panels might need some power sequencing and backlight management,
> so make it possible to associate a drm_panel with an eDP instance and
> prepare and enable the panel accordingly.
> 
> Now that we know which hardware instance is DP and which is eDP,
> parser->parse() is passed the connector_type and the parser is limited
> to only search for a panel in the eDP case.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
> 
> Changes since v3:
> - Previously posted separately, now added to series
> - Make the search for a panel conditional on it being an eDP connector
> - Move the search to of_graph port 1 (was 2 to distinguish from DP
> link to USB-C connector)
> 
>  drivers/gpu/drm/msm/dp/dp_display.c |  9 ++++++---
>  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>  drivers/gpu/drm/msm/dp/dp_drm.c     | 11 +++++++++++
>  drivers/gpu/drm/msm/dp/dp_parser.c  | 30 ++++++++++++++++++++++++++++-
>  drivers/gpu/drm/msm/dp/dp_parser.h  |  3 ++-
>  5 files changed, 49 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c
> b/drivers/gpu/drm/msm/dp/dp_display.c
> index eaf08f9e7d87..bdaf227f05dc 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/drm_panel.h>
> 
>  #include "msm_drv.h"
>  #include "msm_kms.h"
> @@ -230,12 +231,14 @@ static int dp_display_bind(struct device *dev,
> struct device *master,
>  	priv = drm->dev_private;
>  	priv->dp = &(dp->dp_display);
> 
> -	rc = dp->parser->parse(dp->parser);
> +	rc = dp->parser->parse(dp->parser, dp->dp_display.connector_type);
>  	if (rc) {
>  		DRM_ERROR("device tree parsing failed\n");
>  		goto end;
>  	}
> 
> +	dp->dp_display.panel_bridge = dp->parser->panel_bridge;
> +
>  	dp->aux->drm_dev = drm;
>  	rc = dp_aux_register(dp->aux);
>  	if (rc) {
> @@ -822,7 +825,7 @@ static int dp_display_set_mode(struct msm_dp 
> *dp_display,
>  	return 0;
>  }
> 
> -static int dp_display_prepare(struct msm_dp *dp)
> +static int dp_display_prepare(struct msm_dp *dp_display)
>  {
>  	return 0;
>  }
> @@ -896,7 +899,7 @@ static int dp_display_disable(struct
> dp_display_private *dp, u32 data)
>  	return 0;
>  }
> 
> -static int dp_display_unprepare(struct msm_dp *dp)
> +static int dp_display_unprepare(struct msm_dp *dp_display)
>  {
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h
> b/drivers/gpu/drm/msm/dp/dp_display.h
> index 02999408c052..24aefca66029 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -15,6 +15,7 @@ struct msm_dp {
>  	struct device *codec_dev;
>  	struct drm_connector *connector;
>  	struct drm_encoder *encoder;
> +	struct drm_bridge *panel_bridge;
>  	bool is_connected;
>  	bool audio_enabled;
>  	bool power_on;
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c 
> b/drivers/gpu/drm/msm/dp/dp_drm.c
> index f33e31523f56..76856c4ee1d6 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -5,6 +5,7 @@
> 
>  #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"
> @@ -160,5 +161,15 @@ struct drm_connector
> *dp_drm_connector_init(struct msm_dp *dp_display)
> 
>  	drm_connector_attach_encoder(connector, dp_display->encoder);
> 
> +	if (dp_display->panel_bridge) {
> +		ret = drm_bridge_attach(dp_display->encoder,
> +					dp_display->panel_bridge, NULL,
> +					DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +		if (ret < 0) {
> +			DRM_ERROR("failed to attach panel bridge: %d\n", ret);
> +			return ERR_PTR(ret);
> +		}
> +	}
> +
>  	return connector;
>  }
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c
> b/drivers/gpu/drm/msm/dp/dp_parser.c
> index 4d6e047f803d..eb6bbfbea484 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.c
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.c
> @@ -6,6 +6,7 @@
>  #include <linux/of_gpio.h>
>  #include <linux/phy/phy.h>
> 
> +#include <drm/drm_of.h>
>  #include <drm/drm_print.h>
> 
>  #include "dp_parser.h"
> @@ -263,7 +264,28 @@ static int dp_parser_clock(struct dp_parser 
> *parser)
>  	return 0;
>  }
> 
> -static int dp_parser_parse(struct dp_parser *parser)
> +static int dp_parser_find_panel(struct dp_parser *parser)
> +{
> +	struct device *dev = &parser->pdev->dev;
> +	struct drm_panel *panel;
> +	int rc;
> +
> +	rc = drm_of_find_panel_or_bridge(dev->of_node, 1, 0, &panel, NULL);
> +	if (rc) {
> +		DRM_ERROR("failed to acquire DRM panel: %d\n", rc);
> +		return rc;
> +	}
> +
> +	parser->panel_bridge = devm_drm_panel_bridge_add(dev, panel);
> +	if (IS_ERR(parser->panel_bridge)) {
> +		DRM_ERROR("failed to create panel bridge\n");
> +		return PTR_ERR(parser->panel_bridge);
> +	}

When we add a bridge using devm_drm_panel_bridge_add(), it will register 
with default bridge functions which is fine
because we need the panel power to be controlled here.


140 static const struct drm_bridge_funcs panel_bridge_bridge_funcs = {
141 	.attach = panel_bridge_attach,
142 	.detach = panel_bridge_detach,
143 	.pre_enable = panel_bridge_pre_enable,
144 	.enable = panel_bridge_enable,
145 	.disable = panel_bridge_disable,
146 	.post_disable = panel_bridge_post_disable,
147 	.get_modes = panel_bridge_get_modes,

But what about the EDID related things, the DP/eDP driver already reads 
the EDID and gets the modes so we need to skip
that in this case as otherwise it will end up calling the 
panel_get_modes in the eDP panel which will be redundant.

Let me know if I am missing something in this proposal.

> +
> +	return 0;
> +}
> +
> +static int dp_parser_parse(struct dp_parser *parser, int 
> connector_type)
>  {
>  	int rc = 0;
> 
> @@ -284,6 +306,12 @@ static int dp_parser_parse(struct dp_parser 
> *parser)
>  	if (rc)
>  		return rc;
> 
> +	if (connector_type == DRM_MODE_CONNECTOR_eDP) {
> +		rc = dp_parser_find_panel(parser);
> +		if (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 dac10923abde..3172da089421 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.h
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.h
> @@ -123,8 +123,9 @@ struct dp_parser {
>  	struct dp_display_data disp_data;
>  	const struct dp_regulator_cfg *regulator_cfg;
>  	u32 max_dp_lanes;
> +	struct drm_bridge *panel_bridge;
> 
> -	int (*parse)(struct dp_parser *parser);
> +	int (*parse)(struct dp_parser *parser, int connector_type);
>  };
> 
>  /**