linux-kernel - Re: [PATCH v5 09/12] drm/msm/dp: Implement hpd

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Date:   Thu, 8 Dec 2022 15:15:18 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Kalyan Thota <quic_kalyant@...cinc.com>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        "Johan Hovold" <johan+linaro@...nel.org>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        <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 v5 09/12] drm/msm/dp: Implement hpd_notify()


On 12/7/2022 2:00 PM, Bjorn Andersson wrote:
> From: Bjorn Andersson <bjorn.andersson@...aro.org>
>
> The DisplayPort controller's hot-plug mechanism is based on pinmuxing a
> physical signal on 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>
> [bjorn: Drop connector->fwnode assignment and dev from struct msm_dp]
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Reviewed-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>
> Changes since v4:
> - Look at internal_hpd now that it's introduced before this patch.
>
>   drivers/gpu/drm/msm/dp/dp_display.c | 22 ++++++++++++++++++++++
>   drivers/gpu/drm/msm/dp/dp_drm.c     |  1 +
>   drivers/gpu/drm/msm/dp/dp_drm.h     |  2 ++
>   3 files changed, 25 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 095adf528e43..0bee412603fe 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1792,3 +1792,25 @@ void dp_bridge_hpd_disable(struct drm_bridge *bridge)
>   
>   	dp_display->internal_hpd = false;
>   }
> +
> +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->internal_hpd)
> +		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_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index 9d03b6ee3c41..275370f21115 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -104,6 +104,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
>   	.atomic_check = dp_bridge_atomic_check,
>   	.hpd_enable   = dp_bridge_hpd_enable,
>   	.hpd_disable  = dp_bridge_hpd_disable,
> +	.hpd_notify   = dp_bridge_hpd_notify,
>   };
>   
>   struct drm_bridge *dp_bridge_init(struct msm_dp *dp_display, struct drm_device *dev,
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.h b/drivers/gpu/drm/msm/dp/dp_drm.h
> index 1f871b555006..250f7c66201f 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.h
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.h
> @@ -34,5 +34,7 @@ void dp_bridge_mode_set(struct drm_bridge *drm_bridge,
>   			const struct drm_display_mode *adjusted_mode);
>   void dp_bridge_hpd_enable(struct drm_bridge *bridge);
>   void dp_bridge_hpd_disable(struct drm_bridge *bridge);
> +void dp_bridge_hpd_notify(struct drm_bridge *bridge,
> +			  enum drm_connector_status status);
>   
>   #endif /* _DP_DRM_H_ */