drm/hyperv: Handle feature change message from device

Virtual device inform if screen update is needed or not with
SYNTHVID_FEATURE_CHANGE message. Handle this message to set dirt_needed
flag.
Suggested-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Deepak Rawat <drawat.floss@gmail.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210527112230.1274-2-drawat.floss@gmail.com

drivers/gpu/drm/hyperv/hyperv_drm.h

@@ -29,6 +29,7 @@ struct hyperv_drm_device {
 	struct completion wait;
 	u32 synthvid_version;
 	u32 mmio_megabytes;
+	bool dirt_needed;
 
 	u8 init_buf[VMBUS_MAX_PACKET_SIZE];
 	u8 recv_buf[VMBUS_MAX_PACKET_SIZE];

drivers/gpu/drm/hyperv/hyperv_drm_drv.c

@@ -198,6 +198,8 @@ static int hyperv_vmbus_probe(struct hv_device *hdev,
 	if (ret)
 		drm_warn(dev, "Failed to update vram location.\n");
 
+	hv->dirt_needed = true;
+
 	ret = hyperv_mode_config_init(hv);
 	if (ret)
 		goto err_vmbus_close;

drivers/gpu/drm/hyperv/hyperv_drm_proto.c

@@ -301,8 +301,12 @@ int hyperv_update_situation(struct hv_device *hdev, u8 active, u32 bpp,
 
 int hyperv_update_dirt(struct hv_device *hdev, struct drm_rect *rect)
 {
+	struct hyperv_drm_device *hv = hv_get_drvdata(hdev);
 	struct synthvid_msg msg;
 
+	if (!hv->dirt_needed)
+		return 0;
+
 	memset(&msg, 0, sizeof(struct synthvid_msg));
 
 	msg.vid_hdr.type = SYNTHVID_DIRT;
@@ -387,6 +391,9 @@ static void hyperv_receive_sub(struct hv_device *hdev)
 		complete(&hv->wait);
 		return;
 	}
+
+	if (msg->vid_hdr.type == SYNTHVID_FEATURE_CHANGE)
+		hv->dirt_needed = msg->feature_chg.is_dirt_needed;
 }
 
 static void hyperv_receive(void *ctx)