linux-kernel - Re: [PATCH v4 08/13] drm/msm/dp: Implement hpd

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Message-ID: <4E586110-168A-4D47-966F-357DF042AFC7@linaro.org>
Date:   Tue, 06 Dec 2022 00:29:13 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
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>,
        Kuogee Hsieh <quic_khsieh@...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 v4 08/13] drm/msm/dp: Implement hpd_notify()



On 5 December 2022 20:44:28 GMT+03:00, Bjorn Andersson <quic_bjorande@...cinc.com> 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>

Minor nit: if for the next revision you reorder the patches to have hpd_enable first, then missing conditions, then this patch, it will look more logical.

>---
>
>Changes since v3:
>- None
>
> 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 666b45c8ab80..17fcf8cd84cd 100644
>--- a/drivers/gpu/drm/msm/dp/dp_display.c
>+++ b/drivers/gpu/drm/msm/dp/dp_display.c
>@@ -1772,3 +1772,25 @@ 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_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
>index 6db82f9b03af..3898366ebd5e 100644
>--- a/drivers/gpu/drm/msm/dp/dp_drm.c
>+++ b/drivers/gpu/drm/msm/dp/dp_drm.c
>@@ -102,6 +102,7 @@ static const struct drm_bridge_funcs dp_bridge_ops = {
> 	.get_modes    = dp_bridge_get_modes,
> 	.detect       = dp_bridge_detect,
> 	.atomic_check = dp_bridge_atomic_check,
>+	.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 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