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

[Stephen Boyd <swboyd@chromium.org>]

Quoting Bjorn Andersson (2021-07-26 16:13:51)
> 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>
> ---
>
> 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.

dianders@ mentioned creating a connector (and maybe a bridge) for the DP
connector (not eDP)[1]. I'm not sure that's directly related, but I
think with the aux bus code the panel isn't managed in the encoder
driver. Instead the encoder sees a bridge and tries to power it up and
then query things over the aux bus? It's all a little too fuzzy to me
right now so I could be spewing nonsense but I think we want to take
this bridge route if possible.

-Stephen

[1] https://lore.kernel.org/r/CAD=FV=Xd9fizYdxfXYOkpJ_1fZcHp3-ROJ7k4iPg0g0RQ_+A3Q@mail.gmail.com/

>
>  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);
>  };
> --