Change to unsigned and reduce latency

ms912x.h

@@ -26,7 +26,8 @@ struct ms912x_device {
 
 	struct drm_connector connector;
 	struct drm_simple_display_pipe display_pipe;
-
+
+	struct completion urb_completion;
 	struct drm_rect update_rect;
 	void *transfer_buffer;
 	int num_urbs;

ms912x_drv.c

@@ -162,7 +162,9 @@ int ms912x_pipe_check(struct drm_simple_display_pipe *pipe,
 	return 0;
 }
 
-static void ms912x_merge_rects(struct drm_rect* dest, struct drm_rect* r1, struct drm_rect* r2) {
+static void ms912x_merge_rects(struct drm_rect *dest, struct drm_rect *r1,
+			       struct drm_rect *r2)
+{
 	dest->x1 = min(r1->x1, r2->x1);
 	dest->y1 = min(r1->y1, r2->y1);
 	dest->x2 = max(r1->x2, r2->x2);
@@ -205,7 +207,8 @@ static const uint32_t ms912x_pipe_formats[] = {
 static int ms912x_usb_probe(struct usb_interface *interface,
 			    const struct usb_device_id *id)
 {
-	int ret, i;
+	int ret;
+	unsigned int i;
 	struct ms912x_device *ms912x;
 	struct drm_device *dev;
 
@@ -243,7 +246,10 @@ static int ms912x_usb_probe(struct usb_interface *interface,
 		ms912x_read_byte(ms912x, i);
 	}
 
-	ms912x_init_urb(ms912x, 100 * MS912X_MAX_TRANSFER_LENGTH);
+	// Enough to send a full frame of 1920x1080
+	ms912x_init_urb(ms912x, 64);
+
+	init_completion(&ms912x->urb_completion);
 
 	ret = ms912x_connector_init(ms912x);
 	if (ret)

ms912x_transfer.c

@@ -8,7 +8,7 @@
 
 void ms912x_free_urb(struct ms912x_device *ms912x)
 {
-	int i, blocks;
+	unsigned int i, blocks;
 	struct ms912x_urb *urb_entry;
 	struct usb_device *usb_dev = interface_to_usbdev(ms912x->intf);
 	blocks = ms912x->num_urbs;
@@ -39,17 +39,17 @@ void ms912x_urb_completion(struct urb *urb)
 	list_add_tail(&urb_entry->entry, &ms912x->urb_available_list);
 	spin_unlock_irqrestore(&ms912x->urb_available_list_lock, flags);
 	up(&ms912x->urb_available_list_sem);
+	complete(&ms912x->urb_completion);
 }
 
-int ms912x_init_urb(struct ms912x_device *ms912x, size_t total_size)
+int ms912x_init_urb(struct ms912x_device *ms912x, size_t blocks)
 {
-	int i, blocks;
+	unsigned int i;
 	struct ms912x_urb *urb_entry;
 	struct urb *urb;
 	void *urb_buf;
 	struct usb_device *usb_dev = interface_to_usbdev(ms912x->intf);
 
-	blocks = DIV_ROUND_UP(total_size, MS912X_MAX_TRANSFER_LENGTH);
 	spin_lock_init(&ms912x->urb_available_list_lock);
 	INIT_LIST_HEAD(&ms912x->urb_available_list);
 	sema_init(&ms912x->urb_available_list_sem, 0);
@@ -106,29 +106,32 @@ struct urb *ms912x_get_urb(struct ms912x_device *ms912x)
 	return urb_entry->urb;
 }
 
-static inline int ms912x_rgb_to_y(int r, int g, int b)
+static inline unsigned int ms912x_rgb_to_y(unsigned int r, unsigned int g,
+					   unsigned int b)
 {
-	const int luma = (16 << 16) + 16763 * r + 32904 * g + 6391 * b;
+	const unsigned int luma = (16 << 16) + 16763 * r + 32904 * g + 6391 * b;
 	return luma >> 16;
 }
-static inline int ms912x_rgb_to_u(int r, int g, int b)
+static inline unsigned int ms912x_rgb_to_u(unsigned int r, unsigned int g,
+					   unsigned int b)
 {
-	const int u = (128 << 16) - 9676 * r - 18996 * g + 28672 * b;
+	const unsigned int u = (128 << 16) - 9676 * r - 18996 * g + 28672 * b;
 	return u >> 16;
 }
-static inline int ms912x_rgb_to_v(int r, int g, int b)
+static inline unsigned int ms912x_rgb_to_v(unsigned int r, unsigned int g,
+					   unsigned int b)
 {
-	const int v = (128 << 16) + 28672 * r - 24009 * g - 4663 * b;
+	const unsigned int v = (128 << 16) + 28672 * r - 24009 * g - 4663 * b;
 	return v >> 16;
 }
 
 static int ms912x_xrgb_to_yuv422_line(u8 *transfer_buffer, u32 *xrgb_buffer,
 				      size_t len)
 {
-	int i, offset = 0;
+	unsigned int i, offset = 0;
 	unsigned int pixel1, pixel2;
-	int r1, g1, b1, r2, g2, b2;
-	int v, y1, u, y2;
+	unsigned int r1, g1, b1, r2, g2, b2;
+	unsigned int v, y1, u, y2;
 	for (i = 0; i < len; i += 2) {
 		pixel1 = xrgb_buffer[i];
 		pixel2 = xrgb_buffer[i + 1];
@@ -218,6 +221,7 @@ void ms912x_fb_send_rect(struct drm_framebuffer *fb,
 	transfer_blocks =
 		DIV_ROUND_UP(total_length, MS912X_MAX_TRANSFER_LENGTH);
 
+	reinit_completion(&ms912x->urb_completion);
 	for (i = 0; i < transfer_blocks; i++) {
 		/* Last block may be shorter */
 		urb = ms912x_get_urb(ms912x);
@@ -238,6 +242,12 @@ void ms912x_fb_send_rect(struct drm_framebuffer *fb,
 			break;
 		}
 	}
+	for (i = 0; i < transfer_blocks; i++) {
+		if (!wait_for_completion_timeout(&ms912x->urb_completion,
+						 msecs_to_jiffies(1000))) {
+			break;
+		}
+	}
 
 	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
 free_transfer_buffer: