[PATCH v5 08/11] drm/amd/display: use drm backlight

["Mario Limonciello (AMD)" <superm1@kernel.org>]

Convert AMD display driver to use the new DRM backlight infrastructure.
This allows brightness control via DRM connector properties.

Includes fixes for backlight resource lifecycle management.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

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 f6610902eee4..55c3838f7ec8 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -86,6 +86,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_uapi.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_backlight.h>
 #include <drm/drm_blend.h>
 #include <drm/drm_fixed.h>
 #include <drm/drm_fourcc.h>
@@ -5549,6 +5550,15 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
 		dm->actual_brightness[aconnector->bl_idx] = real_brightness;
 		dm->brightness[aconnector->bl_idx] = real_brightness;
 	}
+
+	/* Link the registered backlight device to the DRM connector. If
+	 * drm_backlight_alloc() failed earlier in init_helper,
+	 * aconnector->base.backlight is NULL and drm_backlight_link() is a
+	 * no-op.
+	 */
+	drm_backlight_link(aconnector->base.backlight,
+			   dm->backlight_dev[aconnector->bl_idx]);
+
 	drm_dbg_driver(drm, "DM: Registered Backlight device: %s\n", bl_name);
 
 	return 0;
@@ -7993,6 +8003,7 @@ static void amdgpu_dm_connector_destroy(struct drm_connector *connector)
 	}
 
 	if (aconnector->bl_idx != -1) {
+		drm_backlight_link(aconnector->base.backlight, NULL);
 		backlight_device_unregister(dm->backlight_dev[aconnector->bl_idx]);
 		dm->backlight_dev[aconnector->bl_idx] = NULL;
 	}
@@ -8005,6 +8016,10 @@ static void amdgpu_dm_connector_destroy(struct drm_connector *connector)
 	aconnector->dc_sink = NULL;
 
 	drm_dp_cec_unregister_connector(&aconnector->dm_dp_aux.aux);
+	/* DRM core will handle drm_backlight cleanup via:
+	 * drm_connector_unregister() -> drm_backlight_unregister()
+	 * drm_connector_cleanup() -> drm_backlight_free()
+	 */
 	drm_connector_unregister(connector);
 	drm_connector_cleanup(connector);
 	kfree(aconnector->dm_dp_aux.aux.name);
@@ -9254,6 +9269,12 @@ void amdgpu_dm_connector_init_helper(struct amdgpu_display_manager *dm,
 	aconnector->base.state->max_bpc = 16;
 	aconnector->base.state->max_requested_bpc = aconnector->base.state->max_bpc;
 
+	if (connector_type == DRM_MODE_CONNECTOR_eDP) {
+		int r = drm_backlight_alloc(&aconnector->base);
+
+		if (r)
+			drm_err(dm->ddev, "Failed to allocate backlight: %d\n", r);
+	}
 	if (connector_type == DRM_MODE_CONNECTOR_HDMIA) {
 		/* Content Type is currently only implemented for HDMI. */
 		drm_connector_attach_content_type_property(&aconnector->base);
-- 
2.54.0