linux-kernel - Re: [PATCH 5/7] drm/msm/dp: Implement hpd

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Message-ID: <4a73be48-f1cf-a359-7f34-e3271f14ea95@linaro.org>
Date:   Mon, 22 Aug 2022 23:36:00 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>
Cc:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] drm/msm/dp: Implement hpd_notify()

On 10/08/2022 06:50, Bjorn Andersson wrote:
> The DisplayPort controller's hot-plug mechanism is based on pinmuxing a
> physical signal no a GPIO pin into the controller. This is not always
> possible, either because there aren't dedicated GPIOs available or
> because the hot-plug signal is a virtual notification, in cases such as
> USB Type-C.
> 
> For these cases, by implementing the hpd_notify() callback for the
> DisplayPort controller's drm_bridge, a downstream drm_bridge
> (next_bridge) can be used to track and signal the connection status
> changes.
> 
> This makes it possible to use downstream drm_bridges such as
> display-connector or any virtual mechanism, as long as they are
> implemented as a drm_bridge.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 23 +++++++++++++++++++++++
>   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>   drivers/gpu/drm/msm/dp/dp_drm.c     |  3 +++
>   drivers/gpu/drm/msm/dp/dp_drm.h     |  2 ++
>   4 files changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 699f28f2251e..568295381246 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1303,6 +1303,7 @@ static int dp_display_probe(struct platform_device *pdev)
>   	if (!desc)
>   		return -EINVAL;
>   
> +	dp->dp_display.dev = &pdev->dev;
>   	dp->pdev = pdev;
>   	dp->name = "drm_dp";
>   	dp->id = desc->id;
> @@ -1765,3 +1766,25 @@ void dp_bridge_mode_set(struct drm_bridge *drm_bridge,
>   	dp_display->dp_mode.h_active_low =
>   		!!(dp_display->dp_mode.drm_mode.flags & DRM_MODE_FLAG_NHSYNC);
>   }
> +
> +void dp_bridge_hpd_notify(struct drm_bridge *bridge,
> +			  enum drm_connector_status status)
> +{
> +	struct msm_dp_bridge *dp_bridge = to_dp_bridge(bridge);
> +	struct msm_dp *dp_display = dp_bridge->dp_display;
> +	struct dp_display_private *dp = container_of(dp_display, struct dp_display_private, dp_display);
> +
> +	/* Without next_bridge interrupts are handled by the DP core directly */
> +	if (!dp_display->next_bridge)
> +		return;
> +
> +	if (!dp->core_initialized) {
> +		drm_dbg_dp(dp->drm_dev, "not initialized\n");
> +		return;
> +	}
> +
> +	if (!dp_display->is_connected && status == connector_status_connected)
> +		dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
> +	else if (dp_display->is_connected && status == connector_status_disconnected)
> +		dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
> +}
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index dcedf021f7fe..d7bc537ead31 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -11,6 +11,7 @@
>   #include "disp/msm_disp_snapshot.h"
>   
>   struct msm_dp {
> +	struct device *dev;
>   	struct drm_device *drm_dev;
>   	struct device *codec_dev;
>   	struct drm_bridge *bridge;
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index 6df25f7662e7..875b23910bef 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -68,6 +68,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
>   	.mode_valid   = dp_bridge_mode_valid,
>   	.get_modes    = dp_bridge_get_modes,
>   	.detect       = dp_bridge_detect,
> +	.hpd_notify   = dp_bridge_hpd_notify,
>   };
>   
>   struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct drm_device *dev,
> @@ -138,6 +139,8 @@ struct drm_connector *dp_drm_connector_init(struct msm_dp *dp_display, struct dr
>   	if (IS_ERR(connector))
>   		return connector;
>   
> +	connector->fwnode = fwnode_handle_get(dev_fwnode(dp_display->dev));

Not used anymore, isn't it? Then dp_display->dev also seems unused.

> +
>   	drm_connector_attach_encoder(connector, encoder);
>   
>   	return connector;
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.h b/drivers/gpu/drm/msm/dp/dp_drm.h
> index 82035dbb0578..79e6b2cf2d25 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.h
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.h
> @@ -32,5 +32,7 @@ enum drm_mode_status dp_bridge_mode_valid(struct drm_bridge *bridge,
>   void dp_bridge_mode_set(struct drm_bridge *drm_bridge,
>   			const struct drm_display_mode *mode,
>   			const struct drm_display_mode *adjusted_mode);
> +void dp_bridge_hpd_notify(struct drm_bridge *bridge,
> +			  enum drm_connector_status status);
>   
>   #endif /* _DP_DRM_H_ */

-- 
With best wishes
Dmitry