[PATCH 2/2] drm/amd: Fetch the EDID from _DDC if available for eDP

[Mario Limonciello]

Some manufacturers have intentionally put an EDID that differs from
the EDID on the internal panel on laptops.

Attempt to fetch this EDID if it exists and prefer it over the EDID
that is provided by the panel.

Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h           |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c      | 30 +++++++++++++++++++
 .../gpu/drm/amd/amdgpu/amdgpu_connectors.c    |  5 ++++
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  8 ++++-
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c |  7 +++--
 5 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index c5f3859fd682..99abe12567a4 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1520,6 +1520,7 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev, int xcc_id,
 
 void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps);
 bool amdgpu_acpi_should_gpu_reset(struct amdgpu_device *adev);
+void *amdgpu_acpi_edid(struct amdgpu_device *adev, struct drm_connector *connector);
 void amdgpu_acpi_detect(void);
 void amdgpu_acpi_release(void);
 #else
@@ -1537,6 +1538,7 @@ static inline int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev,
 }
 static inline void amdgpu_acpi_fini(struct amdgpu_device *adev) { }
 static inline bool amdgpu_acpi_should_gpu_reset(struct amdgpu_device *adev) { return false; }
+static inline void *amdgpu_acpi_edid(struct amdgpu_device *adev, struct drm_connector *connector) { return NULL; }
 static inline void amdgpu_acpi_detect(void) { }
 static inline void amdgpu_acpi_release(void) { }
 static inline bool amdgpu_acpi_is_power_shift_control_supported(void) { return false; }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index e550067e5c5d..c106335f1f22 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -1380,6 +1380,36 @@ bool amdgpu_acpi_should_gpu_reset(struct amdgpu_device *adev)
 #endif
 }
 
+/**
+ * amdgpu_acpi_edid
+ * @adev: amdgpu_device pointer
+ * @connector: drm_connector pointer
+ *
+ * Returns the EDID used for the internal panel if present, NULL otherwise.
+ */
+void *
+amdgpu_acpi_edid(struct amdgpu_device *adev, struct drm_connector *connector)
+{
+	struct drm_device *ddev = adev_to_drm(adev);
+	struct acpi_device *acpidev = ACPI_COMPANION(ddev->dev);
+	void *edid;
+	int r;
+
+	if (!acpidev)
+		return NULL;
+
+	if (connector->connector_type != DRM_MODE_CONNECTOR_eDP)
+		return NULL;
+
+	r = acpi_video_get_edid(acpidev, ACPI_VIDEO_DISPLAY_LCD, -1, &edid);
+	if (r < 0) {
+		DRM_DEBUG_DRIVER("Failed to get EDID from ACPI: %d\n", r);
+		return NULL;
+	}
+
+	return kmemdup(edid, r, GFP_KERNEL);
+}
+
 /*
  * amdgpu_acpi_detect - detect ACPI ATIF/ATCS methods
  *
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 9caba10315a8..c7e1563a46d3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -278,6 +278,11 @@ static void amdgpu_connector_get_edid(struct drm_connector *connector)
 	struct amdgpu_device *adev = drm_to_adev(dev);
 	struct amdgpu_connector *amdgpu_connector = to_amdgpu_connector(connector);
 
+	if (amdgpu_connector->edid)
+		return;
+
+	/* if the BIOS specifies the EDID via _DDC, prefer this */
+	amdgpu_connector->edid = amdgpu_acpi_edid(adev, connector);
 	if (amdgpu_connector->edid)
 		return;
 
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index cd98b3565178..1faa21f542bd 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6562,17 +6562,23 @@ static void amdgpu_dm_connector_funcs_force(struct drm_connector *connector)
 {
 	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
 	struct amdgpu_connector *amdgpu_connector = to_amdgpu_connector(connector);
+	struct amdgpu_device *adev = drm_to_adev(connector->dev);
 	struct dc_link *dc_link = aconnector->dc_link;
 	struct dc_sink *dc_em_sink = aconnector->dc_em_sink;
 	struct edid *edid;
 
+	/* prefer ACPI over panel for eDP */
+	edid = amdgpu_acpi_edid(adev, connector);
+
 	/*
 	 * Note: drm_get_edid gets edid in the following order:
 	 * 1) override EDID if set via edid_override debugfs,
 	 * 2) firmware EDID if set via edid_firmware module parameter
 	 * 3) regular DDC read.
 	 */
-	edid = drm_get_edid(connector, &amdgpu_connector->ddc_bus->aux.ddc);
+	if (!edid)
+		edid = drm_get_edid(connector, &amdgpu_connector->ddc_bus->aux.ddc);
+
 	if (!edid) {
 		DRM_ERROR("No EDID found on connector: %s.\n", connector->name);
 		return;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index e3915c4f8566..6bf2a8867e76 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -895,6 +895,7 @@ enum dc_edid_status dm_helpers_read_local_edid(
 {
 	struct amdgpu_dm_connector *aconnector = link->priv;
 	struct drm_connector *connector = &aconnector->base;
+	struct amdgpu_device *adev = drm_to_adev(connector->dev);
 	struct i2c_adapter *ddc;
 	int retry = 3;
 	enum dc_edid_status edid_status;
@@ -909,8 +910,10 @@ enum dc_edid_status dm_helpers_read_local_edid(
 	 * do check sum and retry to make sure read correct edid.
 	 */
 	do {
-
-		edid = drm_get_edid(&aconnector->base, ddc);
+		/* prefer ACPI over panel for eDP */
+		edid = amdgpu_acpi_edid(adev, connector);
+		if (!edid)
+			edid = drm_get_edid(&aconnector->base, ddc);
 
 		/* DP Compliance Test 4.2.2.6 */
 		if (link->aux_mode && connector->edid_corrupt)
-- 
2.34.1