From 8f30a31be373f6a6e6c143bfa5efa829eace64dc Mon Sep 17 00:00:00 2001
From: William Wu <william.wu@rock-chips.com>
Date: Tue, 19 Dec 2017 14:56:00 +0800
Subject: [PATCH] ANDROID: usb: gadget: f_mtp: add module parameter for Rx
 transfer length

This patch backport from https://android.googlesource.com/kernel/msm
android-msm-wahoo-4.4-oreo-mr1
commit 1bb8887af8b525e68d9c9e7c828836a3d17ab0b3

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 1048576 > /sys/module/usb_f_mtp/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: If5a7d4a167ec4a9e080fcd10caa95884d765a3b6
Signed-off-by: William Wu <william.wu@rock-chips.com>
---
 drivers/usb/gadget/function/f_mtp.c | 32 +++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/gadget/function/f_mtp.c b/drivers/usb/gadget/function/f_mtp.c
index 0aa87bca51e7..02705e1aa3af 100644
--- a/drivers/usb/gadget/function/f_mtp.c
+++ b/drivers/usb/gadget/function/f_mtp.c
@@ -74,6 +74,9 @@
 #define MTP_RESPONSE_DEVICE_BUSY    0x2019
 #define DRIVER_NAME "mtp"
 
+static unsigned int mtp_rx_req_len = MTP_BULK_BUFFER_SIZE;
+module_param(mtp_rx_req_len, uint, 0644);
+
 static const char mtp_shortname[] = DRIVER_NAME "_usb";
 
 struct mtp_dev {
@@ -510,10 +513,27 @@ 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; 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;
 	}
@@ -561,7 +581,7 @@ 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;
 		}
@@ -853,8 +873,8 @@ 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;
 			ret = usb_ep_queue(dev->ep_out, read_req, GFP_KERNEL);
 			if (ret < 0) {