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Message-Id: <20250930090920.131094-12-damon.ding@rock-chips.com>
Date: Tue, 30 Sep 2025 17:09:13 +0800
From: Damon Ding <damon.ding@...k-chips.com>
To: andrzej.hajda@...el.com,
neil.armstrong@...aro.org,
rfoss@...nel.org
Cc: Laurent.pinchart@...asonboard.com,
jonas@...boo.se,
jernej.skrabec@...il.com,
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tzimmermann@...e.de,
airlied@...il.com,
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inki.dae@...sung.com,
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Damon Ding <damon.ding@...k-chips.com>
Subject: [PATCH v6 11/18] drm/display: bridge_connector: Ensure last bridge determines EDID/modes detection capabilities
When multiple bridges are present, EDID detection capability
(DRM_BRIDGE_OP_EDID) takes precedence over modes detection
(DRM_BRIDGE_OP_MODES). To ensure the above two capabilities are
determined by the last bridge in the chain, we handle three cases:
Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES
- If the previous bridge declares DRM_BRIDGE_OP_EDID, set
&drm_bridge_connector.bridge_edid to NULL and set
&drm_bridge_connector.bridge_modes to the later bridge.
- Ensure modes detection capability of the later bridge will not
be ignored.
Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID
- If the previous bridge declares DRM_BRIDGE_OP_MODES, set
&drm_bridge_connector.bridge_modes to NULL and set
&drm_bridge_connector.bridge_edid to the later bridge.
- Although EDID detection capability has higher priority, this
operation is for balance and makes sense.
Case 3: the later bridge declares both of them
- Assign later bridge as &drm_bridge_connector.bridge_edid and
and &drm_bridge_connector.bridge_modes to this bridge.
- Just leave transfer of these two capabilities as before.
Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
---
.../gpu/drm/display/drm_bridge_connector.c | 42 +++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index baacd21e7341..0ca6f140e85b 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -640,6 +640,7 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
struct drm_connector *connector;
struct i2c_adapter *ddc = NULL;
struct drm_bridge *bridge, *panel_bridge = NULL;
+ struct drm_bridge *pre_bridge_edid, *pre_bridge_modes;
unsigned int supported_formats = BIT(HDMI_COLORSPACE_RGB);
unsigned int max_bpc = 8;
bool support_hdcp = false;
@@ -668,6 +669,9 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
*/
connector_type = DRM_MODE_CONNECTOR_Unknown;
drm_for_each_bridge_in_chain(encoder, bridge) {
+ pre_bridge_edid = bridge_connector->bridge_edid;
+ pre_bridge_modes = bridge_connector->bridge_modes;
+
if (!bridge->interlace_allowed)
connector->interlace_allowed = false;
if (!bridge->ycbcr_420_allowed)
@@ -681,6 +685,44 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
bridge_connector->bridge_detect = bridge;
if (bridge->ops & DRM_BRIDGE_OP_MODES)
bridge_connector->bridge_modes = bridge;
+
+ /*
+ * When multiple bridges are present, EDID detection capability
+ * (DRM_BRIDGE_OP_EDID) takes precedence over modes detection
+ * (DRM_BRIDGE_OP_MODES). To ensure the above two capabilities
+ * are determined by the last bridge in the chain, we handle
+ * three cases:
+ *
+ * Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES
+ * - If the previous bridge declares DRM_BRIDGE_OP_EDID, set
+ * &drm_bridge_connector.bridge_edid to NULL and set
+ * &drm_bridge_connector.bridge_modes to the later bridge.
+ * - Ensure modes detection capability of the later bridge
+ * will not be ignored.
+ *
+ * Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID
+ * - If the previous bridge declares DRM_BRIDGE_OP_MODES, set
+ * &drm_bridge_connector.bridge_modes to NULL and set
+ * &drm_bridge_connector.bridge_edid to the later bridge.
+ * - Although EDID detection capability has higher priority,
+ * this operation is for balance and makes sense.
+ *
+ * Case 3: the later bridge declares both of them
+ * - Assign later bridge as &drm_bridge_connector.bridge_edid
+ * and &drm_bridge_connector.bridge_modes to this bridge.
+ * - Just leave transfer of these two capabilities as before.
+ */
+ if (bridge->ops & DRM_BRIDGE_OP_EDID &&
+ !(bridge->ops & DRM_BRIDGE_OP_MODES)) {
+ if (pre_bridge_modes)
+ bridge_connector->bridge_modes = NULL;
+ }
+ if (bridge->ops & DRM_BRIDGE_OP_MODES &&
+ !(bridge->ops & DRM_BRIDGE_OP_EDID)) {
+ if (pre_bridge_edid)
+ bridge_connector->bridge_edid = NULL;
+ }
+
if (bridge->ops & DRM_BRIDGE_OP_HDMI) {
if (bridge_connector->bridge_hdmi)
return ERR_PTR(-EBUSY);
--
2.34.1
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