netdev - [PATCH v5 1/2] net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

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Message-Id: <20220720060518.541-1-lukasz.spintzyk@synaptics.com>
Date:   Wed, 20 Jul 2022 08:05:17 +0200
From:   Łukasz Spintzyk <lukasz.spintzyk@...aptics.com>
To:     netdev@...r.kernel.org
Cc:     linux-usb@...r.kernel.org, oliver@...kum.org, kuba@...nel.org,
        ppd-posix@...aptics.com, Bernice.Chen@...aptics.com
Subject: [PATCH v5 1/2] net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices

From: Dominik Czerwik <dominik.czerwik@...aptics.com>

This improves performance and stability of
DL-3xxx/DL-5xxx/DL-6xxx device series.

Specifically prevents device from temporary network dropouts when
playing video from the web and network traffic going through is high.

Signed-off-by: Dominik Czerwik <dominik.czerwik@...aptics.com>
Signed-off-by: Łukasz Spintzyk <lukasz.spintzyk@...aptics.com>
---
v2: Added Sign-off-by: Bernice Chen as company lawyer.
v3:
  - Remove copyright as this is not really necessary.
  - Removed Sign-off-by: Bernice Chen
v4: No new changes, just resubmit with changed [PATCH v4 2/2]
v5: As asked by Oliver Neukum.
    Mark in original cdc_ncm_info description that it does not send ZLP

 drivers/net/usb/cdc_ncm.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index d55f59ce4a31..8d5cbda33f66 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1892,7 +1892,7 @@ static void cdc_ncm_status(struct usbnet *dev, struct urb *urb)
 }
 
 static const struct driver_info cdc_ncm_info = {
-	.description = "CDC NCM",
+	.description = "CDC NCM (NO ZLP)",
 	.flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
 			| FLAG_LINK_INTR | FLAG_ETHER,
 	.bind = cdc_ncm_bind,
@@ -1904,6 +1904,19 @@ static const struct driver_info cdc_ncm_info = {
 	.set_rx_mode = usbnet_cdc_update_filter,
 };
 
+/* Same as cdc_ncm_info, but with FLAG_SEND_ZLP  */
+static const struct driver_info cdc_ncm_zlp_info = {
+	.description = "CDC NCM (SEND ZLP)",
+	.flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
+			| FLAG_LINK_INTR | FLAG_ETHER | FLAG_SEND_ZLP,
+	.bind = cdc_ncm_bind,
+	.unbind = cdc_ncm_unbind,
+	.manage_power = usbnet_manage_power,
+	.status = cdc_ncm_status,
+	.rx_fixup = cdc_ncm_rx_fixup,
+	.tx_fixup = cdc_ncm_tx_fixup,
+};
+
 /* Same as cdc_ncm_info, but with FLAG_WWAN */
 static const struct driver_info wwan_info = {
 	.description = "Mobile Broadband Network Device",
@@ -2010,6 +2023,16 @@ static const struct usb_device_id cdc_devs[] = {
 	  .driver_info = (unsigned long)&wwan_info,
 	},
 
+	/* DisplayLink docking stations */
+	{ .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
+		| USB_DEVICE_ID_MATCH_VENDOR,
+	  .idVendor = 0x17e9,
+	  .bInterfaceClass = USB_CLASS_COMM,
+	  .bInterfaceSubClass = USB_CDC_SUBCLASS_NCM,
+	  .bInterfaceProtocol = USB_CDC_PROTO_NONE,
+	  .driver_info = (unsigned long)&cdc_ncm_zlp_info,
+	},
+
 	/* Generic CDC-NCM devices */
 	{ USB_INTERFACE_INFO(USB_CLASS_COMM,
 		USB_CDC_SUBCLASS_NCM, USB_CDC_PROTO_NONE),
-- 
2.36.1