USB Speed Improvement

external/patches/linux/0018-Improve-f_accessory-write-queue-handling.patch

@@ -0,0 +1,101 @@
+From 47822c33905518870488414be4255301c536dec7 Mon Sep 17 00:00:00 2001
+From: Augment Agent <agent@augmentcode.com>
+Date: Mon, 16 Mar 2026 23:10:00 +0000
+Subject: [PATCH] usb: gadget: improve accessory write queue handling
+
+
+---
+ drivers/usb/gadget/function/f_accessory.c | 36 ++++++++++----------
+ 1 file changed, 18 insertions(+), 18 deletions(-)
+
+diff --git a/drivers/usb/gadget/function/f_accessory.c b/drivers/usb/gadget/function/f_accessory.c
+index ce7814c..14be99b 100644
+--- a/drivers/usb/gadget/function/f_accessory.c
++++ b/drivers/usb/gadget/function/f_accessory.c
+@@ -55,7 +55,7 @@
+ #define INTERFACE_STRING_INDEX	0
+
+ /* number of tx and rx requests to allocate */
+-#define TX_REQ_MAX 4
++#define TX_REQ_MAX 16  // was likely 4 or 8
+ #define RX_REQ_MAX 2
+
+ struct acc_hid_dev {
+@@ -790,21 +790,28 @@ static ssize_t acc_write(struct file *fp, const char __user *buf,
+ 	ssize_t r = count;
+ 	unsigned xfer;
+ 	int ret;
++	int submitted = 0;
+
+ 	pr_debug("acc_write(%zu)\n", count);
+
+ 	if (!dev->online || dev->disconnected) {
+-		pr_debug("acc_write disconnected or not online");
+ 		return -ENODEV;
+ 	}
+
+ 	while (count > 0) {
+-		/* get an idle tx request to use */
+-		req = 0;
+-		ret = wait_event_interruptible(dev->write_wq,
+-			((req = req_get(dev, &dev->tx_idle)) || !dev->online));
++		/* Only wait if we've saturated the queue */
++		if (submitted >= TX_REQ_MAX - 1) {
++			ret = wait_event_interruptible(dev->write_wq,
++				((req = req_get(dev, &dev->tx_idle)) || !dev->online));
++		} else {
++			req = req_get(dev, &dev->tx_idle);
++			if (!req) {
++				ret = wait_event_interruptible(dev->write_wq,
++					((req = req_get(dev, &dev->tx_idle)) || !dev->online));
++			}
++		}
++		
+ 		if (!dev->online || dev->disconnected) {
+-			pr_debug("acc_write dev->error\n");
+ 			r = -EIO;
+ 			break;
+ 		}
+@@ -816,16 +823,14 @@ static ssize_t acc_write(struct file *fp, const char __user *buf,
+
+ 		if (count > BULK_BUFFER_SIZE) {
+ 			xfer = BULK_BUFFER_SIZE;
+-			/* ZLP, They will be more TX requests so not yet. */
+ 			req->zero = 0;
+ 		} else {
+ 			xfer = count;
+-			/* If the data length is a multple of the
+-			 * maxpacket size then send a zero length packet(ZLP).
+-			*/
+ 			req->zero = ((xfer % dev->ep_in->maxpacket) == 0);
+ 		}
++		
+ 		if (copy_from_user(req->buf, buf, xfer)) {
++			req_put(dev, &dev->tx_idle, req);
+ 			r = -EFAULT;
+ 			break;
+ 		}
+@@ -833,21 +838,16 @@ static ssize_t acc_write(struct file *fp, const char __user *buf,
+ 		req->length = xfer;
+ 		ret = usb_ep_queue(dev->ep_in, req, GFP_KERNEL);
+ 		if (ret < 0) {
+-			pr_debug("acc_write: xfer error %d\n", ret);
++			req_put(dev, &dev->tx_idle, req);
+ 			r = -EIO;
+ 			break;
+ 		}
+
+ 		buf += xfer;
+ 		count -= xfer;
+-
+-		/* zero this so we don't try to free it on error exit */
+-		req = 0;
++		submitted++;
+ 	}
+
+-	if (req)
+-		req_put(dev, &dev->tx_idle, req);
+-
+ 	pr_debug("acc_write returning %zd\n", r);
+ 	return r;
+ }