drm: apple: backlight: force backlight update after resume

If the DCP firmware indicates that it didn't restore the
brightness, schedule an update.  Wait for 1 frame duration and
check if the brightness update has been taken care of by a swap
that happened in the meantime.
Fixes restoring the brightness after resume when running on a
dumb framebuffer where swaps may not happen for a very long time.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>

Author: kettenis

drivers/gpu/drm/apple/dcp-internal.h

@@ -212,6 +212,8 @@ struct apple_dcp {
 	/* Workqueue for updating the initial initial brightness */
 	struct work_struct bl_register_wq;
 	struct mutex bl_register_mutex;
+	/* Workqueue for updating the brightness */
+	struct work_struct bl_update_wq;
 
 	/* integrated panel if present */
 	struct dcp_panel panel;
@@ -241,6 +243,7 @@ struct apple_dcp {
 };
 
 int dcp_backlight_register(struct apple_dcp *dcp);
+int dcp_backlight_update(struct apple_dcp *dcp);
 bool dcp_has_panel(struct apple_dcp *dcp);
 
 #define DCP_AUDIO_MAX_CHANS 15

drivers/gpu/drm/apple/dcp.c

@@ -515,6 +515,15 @@ static void dcp_work_register_backlight(struct work_struct *work)
 	mutex_unlock(&dcp->bl_register_mutex);
 }
 
+static void dcp_work_update_backlight(struct work_struct *work)
+{
+	struct apple_dcp *dcp;
+
+	dcp = container_of(work, struct apple_dcp, bl_update_wq);
+
+	dcp_backlight_update(dcp);
+}
+
 static int dcp_create_piodma_iommu_dev(struct apple_dcp *dcp)
 {
 	int ret;
@@ -835,6 +844,7 @@ static int dcp_comp_bind(struct device *dev, struct device *main, void *data)
 		dcp->connector_type = DRM_MODE_CONNECTOR_eDP;
 		INIT_WORK(&dcp->bl_register_wq, dcp_work_register_backlight);
 		mutex_init(&dcp->bl_register_mutex);
+		INIT_WORK(&dcp->bl_update_wq, dcp_work_update_backlight);
 	} else if (of_property_match_string(dev->of_node, "apple,connector-type", "HDMI-A") >= 0)
 		dcp->connector_type = DRM_MODE_CONNECTOR_HDMIA;
 	else if (of_property_match_string(dev->of_node, "apple,connector-type", "DP") >= 0)

drivers/gpu/drm/apple/dcp_backlight.c

@@ -172,20 +172,8 @@ static int drm_crtc_set_brightness(struct apple_dcp *dcp)
 	return ret;
 }
 
-static int dcp_set_brightness(struct backlight_device *bd)
+int dcp_backlight_update(struct apple_dcp *dcp)
 {
-	int ret = 0;
-	struct apple_dcp *dcp = bl_get_data(bd);
-	struct drm_modeset_acquire_ctx ctx;
-	int brightness = backlight_get_brightness(bd);
-
-	DRM_MODESET_LOCK_ALL_BEGIN(dcp->crtc->base.dev, ctx, 0, ret);
-
-	dcp->brightness.dac = calculate_dac(dcp, brightness);
-	dcp->brightness.update = true;
-
-	DRM_MODESET_LOCK_ALL_END(dcp->crtc->base.dev, ctx, ret);
-
 	/*
 	 * Do not actively try to change brightness if no mode is set.
 	 * TODO: should this be reflected the in backlight's power property?
@@ -202,6 +190,23 @@ static int dcp_set_brightness(struct backlight_device *bd)
 	return drm_crtc_set_brightness(dcp);
 }
 
+static int dcp_set_brightness(struct backlight_device *bd)
+{
+	int ret = 0;
+	struct apple_dcp *dcp = bl_get_data(bd);
+	struct drm_modeset_acquire_ctx ctx;
+	int brightness = backlight_get_brightness(bd);
+
+	DRM_MODESET_LOCK_ALL_BEGIN(dcp->crtc->base.dev, ctx, 0, ret);
+
+	dcp->brightness.dac = calculate_dac(dcp, brightness);
+	dcp->brightness.update = true;
+
+	DRM_MODESET_LOCK_ALL_END(dcp->crtc->base.dev, ctx, ret);
+
+	return dcp_backlight_update(dcp);
+}
+
 static const struct backlight_ops dcp_backlight_ops = {
 	.options = BL_CORE_SUSPENDRESUME,
 	.get_brightness = dcp_get_brightness,

drivers/gpu/drm/apple/iomfb_template.c

@@ -497,6 +497,7 @@ static void iomfbep_cb_enable_backlight_message_ap_gated(struct apple_dcp *dcp,
 	 * syslog: "[BrightnessLCD.cpp:743][AFK]nitsToDBV: iDAC out of range"
 	 */
 	dcp->brightness.update = true;
+	schedule_work(&dcp->bl_update_wq);
 }
 
 /* Chunked data transfer for property dictionaries */