Re: [RFC] drm/msm/dp: Allow attaching a drm_panel

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 27/07/2021 02:13, Bjorn Andersson wrote:
> eDP panels might need some power sequencing and backlight management,
> so make it possible to associate a drm_panel with a DP instance and
> prepare and enable the panel accordingly.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>

The idea looks good from my point of view. For v1 could you please 
extend it with the `if (panel)` checks and handling of the error codes.

> ---
>
> This solves my immediate problem on my 8cx laptops, of indirectly controlling
> the backlight during DPMS. But my panel is powered when I boot it and as such I
> get the hpd interrupt and I don't actually have to deal with a power on
> sequence - so I'm posting this as an RFC, hoping to get some input on these
> other aspects.
>
> If this is acceptable I'd be happy to write up an accompanying DT binding
> change that marks port 2 of the DP controller's of_graph as a reference to the
> attached panel.
>
>   drivers/gpu/drm/msm/dp/dp_display.c | 15 +++++++++++++--
>   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>   drivers/gpu/drm/msm/dp/dp_parser.c  | 19 +++++++++++++++++++
>   drivers/gpu/drm/msm/dp/dp_parser.h  |  1 +
>   4 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 206bf7806f51..1db5a3f752d2 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"
> @@ -252,6 +253,8 @@ static int dp_display_bind(struct device *dev, struct device *master,
>   		goto end;
>   	}
>   
> +	dp->dp_display.drm_panel = dp->parser->drm_panel;
> +
>   	rc = dp_aux_register(dp->aux, drm);
>   	if (rc) {
>   		DRM_ERROR("DRM DP AUX register failed\n");
> @@ -867,8 +870,10 @@ 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)
>   {
> +	drm_panel_prepare(dp_display->drm_panel);
> +
>   	return 0;
>   }
>   
> @@ -886,6 +891,8 @@ static int dp_display_enable(struct dp_display_private *dp, u32 data)
>   	if (!rc)
>   		dp_display->power_on = true;
>   
> +	drm_panel_enable(dp_display->drm_panel);
> +
>   	return rc;
>   }
>   
> @@ -915,6 +922,8 @@ static int dp_display_disable(struct dp_display_private *dp, u32 data)
>   	if (!dp_display->power_on)
>   		return 0;
>   
> +	drm_panel_disable(dp_display->drm_panel);
> +
>   	/* wait only if audio was enabled */
>   	if (dp_display->audio_enabled) {
>   		/* signal the disconnect event */
> @@ -939,8 +948,10 @@ 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)
>   {
> +	drm_panel_unprepare(dp_display->drm_panel);
> +
>   	return 0;
>   }
>   
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index 8b47cdabb67e..ce337824c95d 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_panel *drm_panel;
>   	bool is_connected;
>   	bool audio_enabled;
>   	bool power_on;
> diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
> index fc8a6452f641..e6a6e9007bfd 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"
> @@ -276,6 +277,20 @@ static int dp_parser_clock(struct dp_parser *parser)
>   	return 0;
>   }
>   
> +static int dp_parser_find_panel(struct dp_parser *parser)
> +{
> +	struct device_node *np = parser->pdev->dev.of_node;
> +	int rc;
> +
> +	rc = drm_of_find_panel_or_bridge(np, 2, 0, &parser->drm_panel, NULL);
> +	if (rc == -ENODEV)
> +		rc = 0;
> +	else if (rc)
> +		DRM_ERROR("failed to acquire DRM panel: %d\n", rc);
> +
> +	return rc;
> +}
> +
>   static int dp_parser_parse(struct dp_parser *parser)
>   {
>   	int rc = 0;
> @@ -297,6 +312,10 @@ static int dp_parser_parse(struct dp_parser *parser)
>   	if (rc)
>   		return rc;
>   
> +	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 3266b529c090..994ca9336acd 100644
> --- a/drivers/gpu/drm/msm/dp/dp_parser.h
> +++ b/drivers/gpu/drm/msm/dp/dp_parser.h
> @@ -122,6 +122,7 @@ struct dp_parser {
>   	struct dp_display_data disp_data;
>   	const struct dp_regulator_cfg *regulator_cfg;
>   	u32 max_dp_lanes;
> +	struct drm_panel *drm_panel;
>   
>   	int (*parse)(struct dp_parser *parser);
>   };


--
With best wishes
Dmitry