[media] af9015: reimplement firmware download

Split FW download packages smarter way and bug free. Implementation is
based of Andrea Merello's example he provided for tda18218 driver.
Count remaining FW bytes down in loop instead of division and modulo
combination used earlier.

Thanks-to: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Cc: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/dvb-usb/af9015.c

@@ -665,9 +665,8 @@ error:
 static int af9015_download_firmware(struct usb_device *udev,
 	const struct firmware *fw)
 {
-	int i, len, packets, remainder, ret;
+	int i, len, remaining, ret;
 	struct req_t req = {DOWNLOAD_FIRMWARE, 0, 0, 0, 0, 0, NULL};
-	u16 addr = 0x5100; /* firmware start address */
 	u16 checksum = 0;
 
 	deb_info("%s:\n", __func__);
@@ -679,24 +678,20 @@ static int af9015_download_firmware(struct usb_device *udev,
 	af9015_config.firmware_size = fw->size;
 	af9015_config.firmware_checksum = checksum;
 
-	#define FW_PACKET_MAX_DATA  55
-
-	packets = fw->size / FW_PACKET_MAX_DATA;
-	remainder = fw->size % FW_PACKET_MAX_DATA;
-	len = FW_PACKET_MAX_DATA;
-	for (i = 0; i <= packets; i++) {
-		if (i == packets)  /* set size of the last packet */
-			len = remainder;
+	#define FW_ADDR 0x5100 /* firmware start address */
+	#define LEN_MAX 55 /* max packet size */
+	for (remaining = fw->size; remaining > 0; remaining -= LEN_MAX) {
+		len = remaining;
+		if (len > LEN_MAX)
+			len = LEN_MAX;
 
 		req.data_len = len;
-		req.data = (u8 *)(fw->data + i * FW_PACKET_MAX_DATA);
-		req.addr = addr;
-		addr += FW_PACKET_MAX_DATA;
+		req.data = (u8 *) &fw->data[fw->size - remaining];
+		req.addr = FW_ADDR + fw->size - remaining;
 
 		ret = af9015_rw_udev(udev, &req);
 		if (ret) {
-			err("firmware download failed at packet %d with " \
-				"code %d", i, ret);
+			err("firmware download failed:%d", ret);
 			goto error;
 		}
 	}