USB: gadget: mtp: Add module parameter for Rx transfer length

The Rx request transfer length is 16K bytes by default.  The test
results indicate that larger transfers improve write speeds.  Add
provision for specifying Rx transfer length at runtime.

echo -n 1048576 > /sys/module/g_android/parameters/mtp_rx_req_len

The above command can be used to set Rx transfer length to 1MB.  If
the memory allocation is failed, fallback to the default length.

Change-Id: I74d5da09437c25e9f1772f7cd49aecb8e4fedcf2
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>

1 files changed, 26 insertions, 6 deletions

diff --git a/drivers/usb/gadget/function/f_mtp.c b/drivers/usb/gadget/function/f_mtp.c
index 286cb7622870..33c6118bf71d 100644
--- a/drivers/usb/gadget/function/f_mtp.c
+++ b/drivers/usb/gadget/function/f_mtp.c
@@ -73,6 +73,9 @@
 #define MTP_RESPONSE_DEVICE_BUSY    0x2019
 #define DRIVER_NAME "mtp"
 
+unsigned int mtp_rx_req_len = MTP_BULK_BUFFER_SIZE;
+module_param(mtp_rx_req_len, uint, S_IRUGO | S_IWUSR);
+
 static const char mtp_shortname[] = DRIVER_NAME "_usb";
 
 struct mtp_dev {
@@ -450,10 +453,27 @@ static int mtp_create_bulk_endpoints(struct mtp_dev *dev,
 		req->complete = mtp_complete_in;
 		mtp_req_put(dev, &dev->tx_idle, req);
 	}
+
+	/*
+	 * The RX buffer should be aligned to EP max packet for
+	 * some controllers.  At bind time, we don't know the
+	 * operational speed.  Hence assuming super speed max
+	 * packet size.
+	 */
+	if (mtp_rx_req_len % 1024)
+		mtp_rx_req_len = MTP_BULK_BUFFER_SIZE;
+
+retry_rx_alloc:
 	for (i = 0; i < RX_REQ_MAX; i++) {
-		req = mtp_request_new(dev->ep_out, MTP_BULK_BUFFER_SIZE);
-		if (!req)
-			goto fail;
+		req = mtp_request_new(dev->ep_out, mtp_rx_req_len);
+		if (!req) {
+			if (mtp_rx_req_len <= MTP_BULK_BUFFER_SIZE)
+				goto fail;
+			for (; i > 0; i--)
+				mtp_request_free(dev->rx_req[i], dev->ep_out);
+			mtp_rx_req_len = MTP_BULK_BUFFER_SIZE;
+			goto retry_rx_alloc;
+		}
 		req->complete = mtp_complete_out;
 		dev->rx_req[i] = req;
 	}
@@ -483,7 +503,7 @@ static ssize_t mtp_read(struct file *fp, char __user *buf,
 
 	DBG(cdev, "mtp_read(%zu)\n", count);
 
-	if (count > MTP_BULK_BUFFER_SIZE)
+	if (count > mtp_rx_req_len)
 		return -EINVAL;
 
 	if (!IS_ALIGNED(count, dev->ep_out->maxpacket))
@@ -511,7 +531,7 @@ static ssize_t mtp_read(struct file *fp, char __user *buf,
 requeue_req:
 	/* queue a request */
 	req = dev->rx_req[0];
-	req->length = MTP_BULK_BUFFER_SIZE;
+	req->length = mtp_rx_req_len;
 	dev->rx_done = 0;
 	ret = usb_ep_queue(dev->ep_out, req, GFP_KERNEL);
 	if (ret < 0) {
@@ -787,7 +807,7 @@ static void receive_file_work(struct work_struct *data)
 			cur_buf = (cur_buf + 1) % RX_REQ_MAX;
 
 			/* some h/w expects size to be aligned to ep's MTU */
-			read_req->length = MTP_BULK_BUFFER_SIZE;
+			read_req->length = mtp_rx_req_len;
 
 			dev->rx_done = 0;
 			ret = usb_ep_queue(dev->ep_out, read_req, GFP_KERNEL);