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Date:   Wed, 25 Aug 2021 18:28:37 -0500
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Kuogee Hsieh <khsieh@codeaurora.org>,
        Abhinav Kumar <abhinavk@codeaurora.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Chandan Uddaraju <chandanu@codeaurora.org>,
        Vara Reddy <varar@codeaurora.org>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC] drm/msm/dp: Allow attaching a drm_panel
Message-ID: <YSbSJbJ51oC447Gb@builder.lan>
References: <20210726231351.655302-1-bjorn.andersson@linaro.org>
 <3bb5dc26-6779-6cb4-b9dd-e64c306e9ae6@linaro.org>
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On Thu 29 Jul 04:59 CDT 2021, Dmitry Baryshkov wrote:

> 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@linaro.org>
> 
> The idea looks good from my point of view.

Thanks.

> For v1 could you please extend it with the `if (panel)` checks and
> handling of the error codes.

Passing NULL to the drm_panel_* api is valid and a nop, and I run the
same code for both eDP and DP.

Would you still like it to indicate to a future reader that this might
be NULL?

Regards,
Bjorn

> 
> > ---
> > 
> > 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