drm: handle override and firmware EDID at drm_do_get_edid() level

Handle debugfs override edid and firmware edid at the low level to
transparently and completely replace the real edid. Previously, we
practically only used the modes from the override EDID, and none of the
other data, such as audio parameters.

This change also prevents actual EDID reads when the EDID is to be
overridden, but retains the DDC probe. This is useful if the reason for
preferring override EDID are problems with reading the data, or
corruption of the data.

Move firmware EDID loading from helper to core, as the functionality
moves to lower level as well. This will result in a change of module
parameter from drm_kms_helper.edid_firmware to drm.edid_firmware, which
arguably makes more sense anyway.

Some future work remains related to override and firmware EDID
validation. Like before, no validation is done for override EDID. The
firmware EDID is validated separately in the loader. Some unification
and deduplication would be in order, to validate all of them at the
drm_do_get_edid() level, like "real" EDIDs.

v2: move firmware loading to core

v3: rebase, commit message refresh

Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1e8a710bcac46e5136c1a7b430074893c81f364a.1505203831.git.jani.nikula@intel.com

Documentation/admin-guide/kernel-parameters.txt

@@ -854,7 +854,7 @@
 			The filter can be disabled or changed to another
 			driver later using sysfs.
 
-	drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
+	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
 			Broken monitors, graphic adapters, KVMs and EDIDless
 			panels may send no or incorrect EDID data sets.
 			This parameter allows to specify an EDID data sets

drivers/gpu/drm/Kconfig

@@ -110,7 +110,7 @@ config DRM_FBDEV_OVERALLOC
 
 config DRM_LOAD_EDID_FIRMWARE
 	bool "Allow to specify an EDID data set instead of probing for it"
-	depends on DRM_KMS_HELPER
+	depends on DRM
 	help
 	  Say Y here, if you want to use EDID data to be loaded from the
 	  /lib/firmware directory or one of the provided built-in

drivers/gpu/drm/Makefile

@@ -28,6 +28,7 @@ drm-$(CONFIG_DRM_PANEL) += drm_panel.o
 drm-$(CONFIG_OF) += drm_of.o
 drm-$(CONFIG_AGP) += drm_agpsupport.o
 drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
+drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 
 drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
@@ -36,7 +37,6 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
 		drm_scdc_helper.o drm_gem_framebuffer_helper.o
 
 drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
-drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
 drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
 drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o

drivers/gpu/drm/drm_edid.c

@@ -1533,6 +1533,10 @@ static void connector_bad_edid(struct drm_connector *connector,
  * level, drivers must make all reasonable efforts to expose it as an I2C
  * adapter and use drm_get_edid() instead of abusing this function.
  *
+ * The EDID may be overridden using debugfs override_edid or firmare EDID
+ * (drm_load_edid_firmware() and drm.edid_firmware parameter), in this priority
+ * order. Having either of them bypasses actual EDID reads.
+ *
  * Return: Pointer to valid EDID or NULL if we couldn't find any.
  */
 struct edid *drm_do_get_edid(struct drm_connector *connector,
@@ -1542,6 +1546,17 @@ struct edid *drm_do_get_edid(struct drm_connector *connector,
 {
 	int i, j = 0, valid_extensions = 0;
 	u8 *edid, *new;
+	struct edid *override = NULL;
+
+	if (connector->override_edid)
+		override = drm_edid_duplicate((const struct edid *)
+					      connector->edid_blob_ptr->data);
+
+	if (!override)
+		override = drm_load_edid_firmware(connector);
+
+	if (!IS_ERR_OR_NULL(override))
+		return override;
 
 	if ((edid = kmalloc(EDID_LENGTH, GFP_KERNEL)) == NULL)
 		return NULL;

drivers/gpu/drm/drm_probe_helper.c

@@ -353,8 +353,6 @@ EXPORT_SYMBOL(drm_helper_probe_detect);
  *    drm_mode_probed_add(). New modes start their life with status as OK.
  *    Modes are added from a single source using the following priority order.
  *
- *    - debugfs 'override_edid' (used for testing only)
- *    - firmware EDID (drm_load_edid_firmware())
  *    - &drm_connector_helper_funcs.get_modes vfunc
  *    - if the connector status is connector_status_connected, standard
  *      VESA DMT modes up to 1024x768 are automatically added
@@ -483,22 +481,7 @@ retry:
 		goto prune;
 	}
 
-	if (connector->override_edid) {
-		struct edid *edid = (struct edid *) connector->edid_blob_ptr->data;
-
-		count = drm_add_edid_modes(connector, edid);
-		drm_edid_to_eld(connector, edid);
-	} else {
-		struct edid *edid = drm_load_edid_firmware(connector);
-		if (!IS_ERR_OR_NULL(edid)) {
-			drm_mode_connector_update_edid_property(connector, edid);
-			count = drm_add_edid_modes(connector, edid);
-			drm_edid_to_eld(connector, edid);
-			kfree(edid);
-		}
-		if (count == 0)
-			count = (*connector_funcs->get_modes)(connector);
-	}
+	count = (*connector_funcs->get_modes)(connector);
 
 	if (count == 0 && connector->status == connector_status_connected)
 		count = drm_add_modes_noedid(connector, 1024, 768);