drm/gm12u320: Simplify upload work

Instead of having a work item that never stops (which really should be
a kthread), with a dedicated workqueue to not upset anyone else, use a
delayed work. A bunch of changes:

- We can throw out all the custom wakeup and requeue logic and state
  tracking. If we schedule the work with a 0 delay it'll get
  scheduled immediately.

- Persistent state (frame & draw_status_timeout) need to be moved out
  of the work.

- diff is bigger than the changes, biggest chunk is reindenting the
  work fn because it lost its while loop.

Lots of code deleting as consequence all over. Specifically we can
delete the drm_driver.release code now!

v2: Review from Hans:
- Use mod_delayed_work in the plane update path to make sure we do
  actually schedule immediately). In the worker we still want
  queue_delayed_work, which won't modify the timeout when the work is
  already scheduled. Which is exactly what we want if the work races
  with a plane update.
- Switch to system_long_wq, Hans says on usb2 a plane upload can take
  80 ms.
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: "Noralf Trønnes" <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-46-daniel.vetter@ffwll.ch

drivers/gpu/drm/tiny/gm12u320.c

@@ -89,13 +89,12 @@ struct gm12u320_device {
 	unsigned char                   *cmd_buf;
 	unsigned char                   *data_buf[GM12U320_BLOCK_COUNT];
 	struct {
-		bool                     run;
-		struct workqueue_struct *workq;
-		struct work_struct       work;
-		wait_queue_head_t        waitq;
+		struct delayed_work       work;
 		struct mutex             lock;
 		struct drm_framebuffer  *fb;
 		struct drm_rect          rect;
+		int frame;
+		int draw_status_timeout;
 	} fb_update;
 };
 
@@ -183,19 +182,9 @@ static int gm12u320_usb_alloc(struct gm12u320_device *gm12u320)
 		       data_block_footer, DATA_BLOCK_FOOTER_SIZE);
 	}
 
-	gm12u320->fb_update.workq = create_singlethread_workqueue(DRIVER_NAME);
-	if (!gm12u320->fb_update.workq)
-		return -ENOMEM;
-
 	return 0;
 }
 
-static void gm12u320_usb_free(struct gm12u320_device *gm12u320)
-{
-	if (gm12u320->fb_update.workq)
-		destroy_workqueue(gm12u320->fb_update.workq);
-}
-
 static int gm12u320_misc_request(struct gm12u320_device *gm12u320,
 				 u8 req_a, u8 req_b,
 				 u8 arg_a, u8 arg_b, u8 arg_c, u8 arg_d)
@@ -338,13 +327,11 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320)
 static void gm12u320_fb_update_work(struct work_struct *work)
 {
 	struct gm12u320_device *gm12u320 =
-		container_of(work, struct gm12u320_device, fb_update.work);
-	int draw_status_timeout = FIRST_FRAME_TIMEOUT;
+		container_of(to_delayed_work(work), struct gm12u320_device,
+			     fb_update.work);
 	int block, block_size, len;
-	int frame = 0;
 	int ret = 0;
 
-	while (gm12u320->fb_update.run) {
 	gm12u320_copy_fb_to_blocks(gm12u320);
 
 	for (block = 0; block < GM12U320_BLOCK_COUNT; block++) {
@@ -358,7 +345,8 @@ static void gm12u320_fb_update_work(struct work_struct *work)
 		gm12u320->cmd_buf[8] = block_size & 0xff;
 		gm12u320->cmd_buf[9] = block_size >> 8;
 		gm12u320->cmd_buf[20] = 0xfc - block * 4;
-			gm12u320->cmd_buf[21] = block | (frame << 7);
+		gm12u320->cmd_buf[21] =
+			block | (gm12u320->fb_update.frame << 7);
 
 		ret = usb_bulk_msg(gm12u320->udev,
 			usb_sndbulkpipe(gm12u320->udev, DATA_SND_EPT),
@@ -396,22 +384,20 @@ static void gm12u320_fb_update_work(struct work_struct *work)
 	ret = usb_bulk_msg(gm12u320->udev,
 		usb_rcvbulkpipe(gm12u320->udev, DATA_RCV_EPT),
 		gm12u320->cmd_buf, READ_STATUS_SIZE, &len,
-			draw_status_timeout);
+		gm12u320->fb_update.draw_status_timeout);
 	if (ret || len != READ_STATUS_SIZE)
 		goto err;
 
-		draw_status_timeout = CMD_TIMEOUT;
-		frame = !frame;
+	gm12u320->fb_update.draw_status_timeout = CMD_TIMEOUT;
+	gm12u320->fb_update.frame = !gm12u320->fb_update.frame;
 
 	/*
 	 * We must draw a frame every 2s otherwise the projector
 	 * switches back to showing its logo.
 	 */
-		wait_event_timeout(gm12u320->fb_update.waitq,
-				   !gm12u320->fb_update.run ||
-					gm12u320->fb_update.fb != NULL,
+	queue_delayed_work(system_long_wq, &gm12u320->fb_update.work,
 			   IDLE_TIMEOUT);
-	}
+
 	return;
 err:
 	/* Do not log errors caused by module unload or device unplug */
@@ -446,36 +432,24 @@ static void gm12u320_fb_mark_dirty(struct drm_framebuffer *fb,
 	mutex_unlock(&gm12u320->fb_update.lock);
 
 	if (wakeup)
-		wake_up(&gm12u320->fb_update.waitq);
+		mod_delayed_work(system_long_wq, &gm12u320->fb_update.work, 0);
 
 	if (old_fb)
 		drm_framebuffer_put(old_fb);
 }
 
-static void gm12u320_start_fb_update(struct gm12u320_device *gm12u320)
-{
-	mutex_lock(&gm12u320->fb_update.lock);
-	gm12u320->fb_update.run = true;
-	mutex_unlock(&gm12u320->fb_update.lock);
-
-	queue_work(gm12u320->fb_update.workq, &gm12u320->fb_update.work);
-}
-
 static void gm12u320_stop_fb_update(struct gm12u320_device *gm12u320)
 {
-	mutex_lock(&gm12u320->fb_update.lock);
-	gm12u320->fb_update.run = false;
-	mutex_unlock(&gm12u320->fb_update.lock);
+	struct drm_framebuffer *old_fb;
 
-	wake_up(&gm12u320->fb_update.waitq);
-	cancel_work_sync(&gm12u320->fb_update.work);
+	cancel_delayed_work_sync(&gm12u320->fb_update.work);
 
 	mutex_lock(&gm12u320->fb_update.lock);
-	if (gm12u320->fb_update.fb) {
-		drm_framebuffer_put(gm12u320->fb_update.fb);
+	old_fb = gm12u320->fb_update.fb;
 	gm12u320->fb_update.fb = NULL;
-	}
 	mutex_unlock(&gm12u320->fb_update.lock);
+
+	drm_framebuffer_put(old_fb);
 }
 
 static int gm12u320_set_ecomode(struct gm12u320_device *gm12u320)
@@ -583,11 +557,11 @@ static void gm12u320_pipe_enable(struct drm_simple_display_pipe *pipe,
 				 struct drm_crtc_state *crtc_state,
 				 struct drm_plane_state *plane_state)
 {
-	struct gm12u320_device *gm12u320 = pipe->crtc.dev->dev_private;
 	struct drm_rect rect = { 0, 0, GM12U320_USER_WIDTH, GM12U320_HEIGHT };
+	struct gm12u320_device *gm12u320 = pipe->crtc.dev->dev_private;
 
+	gm12u320->fb_update.draw_status_timeout = FIRST_FRAME_TIMEOUT;
 	gm12u320_fb_mark_dirty(plane_state->fb, &rect);
-	gm12u320_start_fb_update(gm12u320);
 }
 
 static void gm12u320_pipe_disable(struct drm_simple_display_pipe *pipe)
@@ -622,13 +596,6 @@ static const uint64_t gm12u320_pipe_modifiers[] = {
 	DRM_FORMAT_MOD_INVALID
 };
 
-static void gm12u320_driver_release(struct drm_device *dev)
-{
-	struct gm12u320_device *gm12u320 = dev->dev_private;
-
-	gm12u320_usb_free(gm12u320);
-}
-
 DEFINE_DRM_GEM_FOPS(gm12u320_fops);
 
 static struct drm_driver gm12u320_drm_driver = {
@@ -640,7 +607,6 @@ static struct drm_driver gm12u320_drm_driver = {
 	.major		 = DRIVER_MAJOR,
 	.minor		 = DRIVER_MINOR,
 
-	.release	 = gm12u320_driver_release,
 	.fops		 = &gm12u320_fops,
 	DRM_GEM_SHMEM_DRIVER_OPS,
 };
@@ -670,9 +636,8 @@ static int gm12u320_usb_probe(struct usb_interface *interface,
 		return -ENOMEM;
 
 	gm12u320->udev = interface_to_usbdev(interface);
-	INIT_WORK(&gm12u320->fb_update.work, gm12u320_fb_update_work);
+	INIT_DELAYED_WORK(&gm12u320->fb_update.work, gm12u320_fb_update_work);
 	mutex_init(&gm12u320->fb_update.lock);
-	init_waitqueue_head(&gm12u320->fb_update.waitq);
 
 	dev = &gm12u320->dev;
 	ret = devm_drm_dev_init(&interface->dev, dev, &gm12u320_drm_driver);