[PATCH net] rndis_host: enable RX aggregation for OnePlus Nord CE 2

[Rokas Juras <asrokasjuras@gmail.com>]

USB tethering on the OnePlus Nord CE 2 (IV2201, USB ID 22d9:2766)
running Android 13 has download speeds of approximately 2mbps
with the default 2048-byte receive limit.

The phone's published RNDIS code only enables packet batching
when the computer reports a receive limit above 2048 bytes.
Testing shows that increasing this limit to 2560 bytes
restores normal speeds.

Add a quirk for USB device 22d9:2766 to use and advertise a
receive buffer of at least 16 KiB. This fits the phone code's default
batch of ten packets at a 1500-byte MTU.

Tested on 7.3.0-rc5 with the affected phone, including reconnecting
USB tethering. Download speeds with the change exceed 100mpbs.

Fixes: 7e99eeddb35c ("rndis_host: support WM6 devices as modems")
Link: https://github.com/OnePlusOSS/android_kernel_oneplus_mt6877/blob/3c1e3d432d0c35afa7fded974b50fa6617219e0f/drivers/usb/gadget/function/f_rndis.c#L538-L551
Link: https://github.com/OnePlusOSS/android_kernel_oneplus_mt6877/blob/3c1e3d432d0c35afa7fded974b50fa6617219e0f/drivers/usb/gadget/function/u_ether.c#L869-L874
Assisted-by: LLM
Signed-off-by: Rokas Juras <asrokasjuras@gmail.com>
---
 drivers/net/usb/rndis_host.c   | 21 +++++++++++++++++++++
 include/linux/usb/rndis_host.h |  5 +++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
index 37d4865f5..b001bc834 100644
--- a/drivers/net/usb/rndis_host.c
+++ b/drivers/net/usb/rndis_host.c
@@ -345,6 +345,11 @@ generic_rndis_bind(struct usbnet *dev, struct usb_interface *intf, int flags)
 
 	dev->rx_urb_size = dev->hard_mtu + (dev->maxpacket + 1);
 	dev->rx_urb_size &= ~(dev->maxpacket - 1);
+
+	/* some devices require a receive limit above 2048 for RX aggregation */
+	if (dev->driver_info->data & RNDIS_DRIVER_DATA_RX_AGGREGATION)
+		dev->rx_urb_size = max_t(size_t, dev->rx_urb_size, 16 * 1024);
+
 	u.init->max_transfer_size = cpu_to_le32(dev->rx_urb_size);
 
 	net->netdev_ops = &rndis_netdev_ops;
@@ -612,6 +617,17 @@ static const struct driver_info	rndis_info = {
 	.tx_fixup =	rndis_tx_fixup,
 };
 
+static const struct driver_info	rndis_rx_aggregation_info = {
+	.description =	"RNDIS device",
+	.flags =	FLAG_ETHER | FLAG_POINTTOPOINT | FLAG_FRAMING_RN | FLAG_NO_SETINT,
+	.data =		RNDIS_DRIVER_DATA_RX_AGGREGATION,
+	.bind =		rndis_bind,
+	.unbind =	rndis_unbind,
+	.status =	rndis_status,
+	.rx_fixup =	rndis_rx_fixup,
+	.tx_fixup =	rndis_tx_fixup,
+};
+
 static const struct driver_info	rndis_poll_status_info = {
 	.description =	"RNDIS device (poll status before control)",
 	.flags =	FLAG_ETHER | FLAG_POINTTOPOINT | FLAG_FRAMING_RN | FLAG_NO_SETINT,
@@ -649,6 +665,11 @@ static const struct driver_info	rndis_info_lowpower = {
 
 static const struct usb_device_id	products [] = {
 {
+	/* OnePlus Nord CE 2 */
+	USB_DEVICE_AND_INTERFACE_INFO(0x22d9, 0x2766,
+				      USB_CLASS_WIRELESS_CONTROLLER, 1, 3),
+	.driver_info = (unsigned long)&rndis_rx_aggregation_info,
+}, {
 	/* 2Wire HomePortal 1000SW */
 	USB_DEVICE_AND_INTERFACE_INFO(0x1630, 0x0042,
 				      USB_CLASS_COMM, 2 /* ACM */, 0x0ff),
diff --git a/include/linux/usb/rndis_host.h b/include/linux/usb/rndis_host.h
index 489cfb1d0..3eaf57a9b 100644
--- a/include/linux/usb/rndis_host.h
+++ b/include/linux/usb/rndis_host.h
@@ -182,8 +182,9 @@ struct rndis_keepalive_c {	/* IN (optionally OUT) */
 #define FLAG_RNDIS_PHYM_WIRELESS	0x0002
 
 /* Flags for driver_info::data */
-#define RNDIS_DRIVER_DATA_POLL_STATUS	1	/* poll status before control */
-#define RNDIS_DRIVER_DATA_DST_MAC_FIXUP	2	/* device ignores configured MAC address */
+#define RNDIS_DRIVER_DATA_POLL_STATUS		1	/* poll status before control */
+#define RNDIS_DRIVER_DATA_DST_MAC_FIXUP		2	/* device ignores configured MAC address */
+#define RNDIS_DRIVER_DATA_RX_AGGREGATION	4	/* needs RX limit > 2048 */
 
 extern void rndis_status(struct usbnet *dev, struct urb *urb);
 extern int
-- 
2.55.0