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Date:   Tue, 06 Dec 2022 00:29:13 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To:     Bjorn Andersson <quic_bjorande@quicinc.com>
CC:     Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Kalyan Thota <quic_kalyant@quicinc.com>,
        Jessica Zhang <quic_jesszhan@quicinc.com>,
        Kuogee Hsieh <quic_khsieh@quicinc.com>,
        Johan Hovold <johan+linaro@kernel.org>,
        Sankeerth Billakanti <quic_sbillaka@quicinc.com>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 08/13] drm/msm/dp: Implement hpd_notify()
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On 5 December 2022 20:44:28 GMT+03:00, Bjorn Andersson <quic_bjorande@quic=
inc=2Ecom> wrote:
>From: Bjorn Andersson <bjorn=2Eandersson@linaro=2Eorg>
>
>The DisplayPort controller's hot-plug mechanism is based on pinmuxing a
>physical signal on a GPIO pin into the controller=2E 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=2E
>
>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=2E
>
>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=2E
>
>Signed-off-by: Bjorn Andersson <bjorn=2Eandersson@linaro=2Eorg>
>[bjorn: Drop connector->fwnode assignment and dev from struct msm_dp]
>Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc=2Ecom>

Reviewed-by: Dmitry Baryshkov <dmitry=2Ebaryshkov@linaro=2Eorg>

Minor nit: if for the next revision you reorder the patches to have hpd_en=
able first, then missing conditions, then this patch, it will look more log=
ical=2E

>---
>
>Changes since v3:
>- None
>
> drivers/gpu/drm/msm/dp/dp_display=2Ec | 22 ++++++++++++++++++++++
> drivers/gpu/drm/msm/dp/dp_drm=2Ec     |  1 +
> drivers/gpu/drm/msm/dp/dp_drm=2Eh     |  2 ++
> 3 files changed, 25 insertions(+)
>
>diff --git a/drivers/gpu/drm/msm/dp/dp_display=2Ec b/drivers/gpu/drm/msm/=
dp/dp_display=2Ec
>index 666b45c8ab80=2E=2E17fcf8cd84cd 100644
>--- a/drivers/gpu/drm/msm/dp/dp_display=2Ec
>+++ b/drivers/gpu/drm/msm/dp/dp_display=2Ec
>@@ -1772,3 +1772,25 @@ void dp_bridge_mode_set(struct drm_bridge *drm_bri=
dge,
> 	dp_display->dp_mode=2Eh_active_low =3D
> 		!!(dp_display->dp_mode=2Edrm_mode=2Eflags & DRM_MODE_FLAG_NHSYNC);
> }
>+
>+void dp_bridge_hpd_notify(struct drm_bridge *bridge,
>+			  enum drm_connector_status status)
>+{
>+	struct msm_dp_bridge *dp_bridge =3D to_dp_bridge(bridge);
>+	struct msm_dp *dp_display =3D dp_bridge->dp_display;
>+	struct dp_display_private *dp =3D container_of(dp_display, struct dp_di=
splay_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 =3D=3D connector_status_connect=
ed)
>+		dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
>+	else if (dp_display->is_connected && status =3D=3D connector_status_dis=
connected)
>+		dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
>+}
>diff --git a/drivers/gpu/drm/msm/dp/dp_drm=2Ec b/drivers/gpu/drm/msm/dp/d=
p_drm=2Ec
>index 6db82f9b03af=2E=2E3898366ebd5e 100644
>--- a/drivers/gpu/drm/msm/dp/dp_drm=2Ec
>+++ b/drivers/gpu/drm/msm/dp/dp_drm=2Ec
>@@ -102,6 +102,7 @@ static const struct drm_bridge_funcs dp_bridge_ops =
=3D {
> 	=2Eget_modes    =3D dp_bridge_get_modes,
> 	=2Edetect       =3D dp_bridge_detect,
> 	=2Eatomic_check =3D dp_bridge_atomic_check,
>+	=2Ehpd_notify   =3D dp_bridge_hpd_notify,
> };
>=20
> 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=2Eh b/drivers/gpu/drm/msm/dp/d=
p_drm=2Eh
>index 82035dbb0578=2E=2E79e6b2cf2d25 100644
>--- a/drivers/gpu/drm/msm/dp/dp_drm=2Eh
>+++ b/drivers/gpu/drm/msm/dp/dp_drm=2Eh
>@@ -32,5 +32,7 @@ enum drm_mode_status dp_bridge_mode_valid(struct drm_br=
idge *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);
>=20
> #endif /* _DP_DRM_H_ */

--=20
With best wishes
Dmitry