[PATCH v2 05/11] drm/bridge: dp_typec: Add "no-hpd" support

[Stephen Boyd <swboyd@chromium.org>]

Some EC firmwares on Trogdor/Strongbad boards don't properly indicate
the state of the DP HPD level on a type-c port. The EC only indicates
that DP mode is entered or exited for a type-c port. The HPD state is
expressed to the DP controller via a pin on the AP that the EC drives
high or low when the type-c port partner (i.e. monitor) asserts or
deasserts HPD.

TL;DR: These devices don't support HPD signaling from the type-c code
paths.

Add support for HPD coming from somewhere else in the bridge chain.
Callers can set the struct drm_dp_typec_bridge_desc::no_hpd member to
indicate that HPD shouldn't be signaled from this bridge.

Cc: Prashant Malani <pmalani@chromium.org>
Cc: Benson Leung <bleung@chromium.org>
Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Cc: <chrome-platform@lists.linux.dev>
Cc: Pin-yen Lin <treapking@chromium.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/gpu/drm/bridge/aux-hpd-bridge.c | 12 +++++++++++-
 include/drm/bridge/aux-bridge.h         |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
index 79652d27db40..a5a434b7d5ec 100644
--- a/drivers/gpu/drm/bridge/aux-hpd-bridge.c
+++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
@@ -20,6 +20,7 @@ static DEFINE_IDA(drm_aux_hpd_bridge_ida);
 struct drm_aux_hpd_bridge_data {
 	struct drm_bridge bridge;
 	struct device *dev;
+	bool no_hpd;
 };
 
 enum dp_lane {
@@ -54,6 +55,7 @@ to_drm_dp_typec_bridge_data(struct drm_bridge *bridge)
 struct drm_dp_typec_bridge_dev {
 	struct auxiliary_device adev;
 	size_t max_lanes;
+	bool no_hpd;
 };
 
 static inline struct drm_dp_typec_bridge_dev *
@@ -232,6 +234,7 @@ devm_drm_dp_typec_bridge_alloc(struct device *parent, const struct drm_dp_typec_
 	adev->dev.release = drm_dp_typec_bridge_release;
 	adev->dev.platform_data = of_node_get(desc->of_node);
 	typec_bridge_dev->max_lanes = desc->num_dp_lanes;
+	typec_bridge_dev->no_hpd = desc->no_hpd;
 
 	ret = auxiliary_device_init(adev);
 	if (ret) {
@@ -278,6 +281,8 @@ void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status sta
 
 	if (!data)
 		return;
+	if (data->no_hpd)
+		return;
 
 	drm_bridge_hpd_notify(&data->bridge, status);
 }
@@ -467,6 +472,7 @@ static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
 {
 	struct device *dev = &auxdev->dev;
 	struct drm_aux_hpd_bridge_data *hpd_data;
+	struct drm_dp_typec_bridge_dev *typec_bridge_dev;
 	struct drm_dp_typec_bridge_data *typec_data;
 	struct drm_bridge *bridge;
 	u8 dp_lanes[] = { DP_ML0, DP_ML1, DP_ML2, DP_ML3 };
@@ -477,6 +483,7 @@ static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
 			return -ENOMEM;
 		bridge = &hpd_data->bridge;
 		bridge->funcs = &drm_aux_hpd_bridge_funcs;
+		bridge->ops = DRM_BRIDGE_OP_HPD;
 	} else if (id->driver_data == DRM_AUX_TYPEC_BRIDGE) {
 		typec_data = devm_kzalloc(dev, sizeof(*typec_data), GFP_KERNEL);
 		if (!typec_data)
@@ -484,6 +491,10 @@ static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
 		hpd_data = &typec_data->hpd_bridge;
 		bridge = &hpd_data->bridge;
 		bridge->funcs = &drm_dp_typec_bridge_funcs;
+		typec_bridge_dev = to_drm_dp_typec_bridge_dev(dev);
+		if (!typec_bridge_dev->no_hpd)
+			bridge->ops = DRM_BRIDGE_OP_HPD;
+		hpd_data->no_hpd = typec_bridge_dev->no_hpd;
 		memcpy(typec_data->dp_lanes, dp_lanes, sizeof(typec_data->dp_lanes));
 	} else {
 		return -ENODEV;
@@ -491,7 +502,6 @@ static int drm_aux_hpd_bridge_probe(struct auxiliary_device *auxdev,
 
 	hpd_data->dev = dev;
 	bridge->of_node = dev_get_platdata(dev);
-	bridge->ops = DRM_BRIDGE_OP_HPD;
 	bridge->type = DRM_MODE_CONNECTOR_DisplayPort;
 
 	auxiliary_set_drvdata(auxdev, hpd_data);
diff --git a/include/drm/bridge/aux-bridge.h b/include/drm/bridge/aux-bridge.h
index 258b87c93623..13f5e98b4d31 100644
--- a/include/drm/bridge/aux-bridge.h
+++ b/include/drm/bridge/aux-bridge.h
@@ -28,10 +28,12 @@ struct drm_dp_typec_bridge_dev;
  * struct drm_dp_typec_bridge_desc - drm_dp_typec_bridge descriptor
  * @of_node: device node pointer corresponding to this bridge instance
  * @num_dp_lanes: number of input DP lanes possible (1, 2 or 4)
+ * @no_hpd: true if this bridge can't signal HPD state with drm_dp_typec_bridge_notify()
  */
 struct drm_dp_typec_bridge_desc {
 	struct device_node *of_node;
 	size_t num_dp_lanes;
+	bool no_hpd;
 };
 
 enum usb_ss_lane {
-- 
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