[PATCH 2/2] drm/i915: Prevent HW access during init from connector get_modes hooks

[Imre Deak]

Prevent accessing the HW from the get_modes hooks of connectors deriving
the mode list from the display's EDID. drm_edid_connector_add_modes()
will return the mode list based on the EDID which was cached during a
previous detection/get_modes call.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10085
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_crt.c    | 7 +++++++
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 4 ++++
 drivers/gpu/drm/i915/display/intel_dvo.c    | 5 +++++
 drivers/gpu/drm/i915/display/intel_sdvo.c   | 4 ++++
 4 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_crt.c b/drivers/gpu/drm/i915/display/intel_crt.c
index b9733a73e21d4..27c5595e5d6bc 100644
--- a/drivers/gpu/drm/i915/display/intel_crt.c
+++ b/drivers/gpu/drm/i915/display/intel_crt.c
@@ -646,9 +646,13 @@ static const struct drm_edid *intel_crt_get_edid(struct drm_connector *connector
 static int intel_crt_ddc_get_modes(struct drm_connector *connector,
 				   struct i2c_adapter *ddc)
 {
+	struct drm_i915_private *i915 = to_i915(connector->dev);
 	const struct drm_edid *drm_edid;
 	int ret;
 
+	if (!intel_display_driver_check_access(i915))
+		return drm_edid_connector_add_modes(connector);
+
 	drm_edid = intel_crt_get_edid(connector, ddc);
 	if (!drm_edid)
 		return 0;
@@ -933,6 +937,9 @@ static int intel_crt_get_modes(struct drm_connector *connector)
 	struct i2c_adapter *ddc;
 	int ret;
 
+	if (!intel_display_driver_check_access(dev_priv))
+		return drm_edid_connector_add_modes(connector);
+
 	wakeref = intel_display_power_get(dev_priv,
 					  intel_encoder->power_domain);
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 5fa25a5a36b55..5307ddd4edcf5 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -1197,6 +1197,7 @@ static bool intel_dp_mst_initial_fastset_check(struct intel_encoder *encoder,
 static int intel_dp_mst_get_ddc_modes(struct drm_connector *connector)
 {
 	struct intel_connector *intel_connector = to_intel_connector(connector);
+	struct drm_i915_private *i915 = to_i915(intel_connector->base.dev);
 	struct intel_dp *intel_dp = intel_connector->mst_port;
 	const struct drm_edid *drm_edid;
 	int ret;
@@ -1204,6 +1205,9 @@ static int intel_dp_mst_get_ddc_modes(struct drm_connector *connector)
 	if (drm_connector_is_unregistered(connector))
 		return intel_connector_update_modes(connector, NULL);
 
+	if (!intel_display_driver_check_access(i915))
+		return drm_edid_connector_add_modes(connector);
+
 	drm_edid = drm_dp_mst_edid_read(connector, &intel_dp->mst_mgr, intel_connector->port);
 
 	ret = intel_connector_update_modes(connector, drm_edid);
diff --git a/drivers/gpu/drm/i915/display/intel_dvo.c b/drivers/gpu/drm/i915/display/intel_dvo.c
index 8ca9ae4798a89..c076da75b066e 100644
--- a/drivers/gpu/drm/i915/display/intel_dvo.c
+++ b/drivers/gpu/drm/i915/display/intel_dvo.c
@@ -30,6 +30,7 @@
 
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>
+#include <drm/drm_edid.h>
 
 #include "i915_drv.h"
 #include "i915_reg.h"
@@ -338,8 +339,12 @@ intel_dvo_detect(struct drm_connector *_connector, bool force)
 static int intel_dvo_get_modes(struct drm_connector *_connector)
 {
 	struct intel_connector *connector = to_intel_connector(_connector);
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
 	int num_modes;
 
+	if (!intel_display_driver_check_access(i915))
+		return drm_edid_connector_add_modes(&connector->base);
+
 	/*
 	 * We should probably have an i2c driver get_modes function for those
 	 * devices which will have a fixed set of modes determined by the chip
diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c b/drivers/gpu/drm/i915/display/intel_sdvo.c
index ccea0efbd136f..dae5abf56bbf5 100644
--- a/drivers/gpu/drm/i915/display/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
@@ -2189,12 +2189,16 @@ intel_sdvo_detect(struct drm_connector *connector, bool force)
 
 static int intel_sdvo_get_ddc_modes(struct drm_connector *connector)
 {
+	struct drm_i915_private *i915 = to_i915(connector->dev);
 	int num_modes = 0;
 	const struct drm_edid *drm_edid;
 
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
 
+	if (!intel_display_driver_check_access(i915))
+		return drm_edid_connector_add_modes(connector);
+
 	/* set the bus switch and get the modes */
 	drm_edid = intel_sdvo_get_edid(connector);
 
-- 
2.39.2