USB: gadget: 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.

CRs-Fixed: 429212
Change-Id: I7bed5aeefabf1a50c08a9a8e5b876e0cf59515fd
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>

diff --git a/drivers/usb/gadget/f_mtp.c b/drivers/usb/gadget/f_mtp.c
index 9dc1cc9e37a923447f8d43f608a646ffaf3b36da..7a697f757382a388aa5be6fd964b168fcbde85d5 100644 (file)
--- a/drivers/usb/gadget/f_mtp.c
+++ b/drivers/usb/gadget/f_mtp.c
@@ -67,6 +67,9 @@
 #define MTP_RESPONSE_OK             0x2001
 #define MTP_RESPONSE_DEVICE_BUSY    0x2019
 
+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[] = "mtp_usb";
 
 struct mtp_dev {
@@ -504,10 +507,27 @@ 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;
        }
@@ -553,7 +573,7 @@ static ssize_t mtp_read(struct file *fp, char __user *buf,
        spin_lock_irq(&dev->lock);
        if (dev->ep_out->desc) {
                len = usb_ep_align_maybe(cdev->gadget, dev->ep_out, count);
-               if (len > MTP_BULK_BUFFER_SIZE) {
+               if (len > mtp_rx_req_len) {
                        spin_unlock_irq(&dev->lock);
                        return -EINVAL;
                }
@@ -846,8 +866,8 @@ static void receive_file_work(struct work_struct *data)
                        read_req = dev->rx_req[cur_buf];
                        cur_buf = (cur_buf + 1) % RX_REQ_MAX;
 
-                       read_req->length = (count > MTP_BULK_BUFFER_SIZE
-                                       ? MTP_BULK_BUFFER_SIZE : count);
+                       read_req->length = (count > mtp_rx_req_len
+                                       ? mtp_rx_req_len : count);
                        dev->rx_done = 0;
 
                        set_read_req_length(read_req);