net: usb: cdc_ncm: don't spew notifications

RTL8156 sends notifications about every 32ms.
Only display/log notifications when something changes.

This issue has been reported by others:
	https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1832472
	https://lkml.org/lkml/2020/8/27/1083

...
[785962.779840] usb 1-1: new high-speed USB device number 5 using xhci_hcd
[785962.929944] usb 1-1: New USB device found, idVendor=0bda, idProduct=8156, bcdDevice=30.00
[785962.929949] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=6
[785962.929952] usb 1-1: Product: USB 10/100/1G/2.5G LAN
[785962.929954] usb 1-1: Manufacturer: Realtek
[785962.929956] usb 1-1: SerialNumber: 000000001
[785962.991755] usbcore: registered new interface driver cdc_ether
[785963.017068] cdc_ncm 1-1:2.0: MAC-Address: 00:24:27:88:08:15
[785963.017072] cdc_ncm 1-1:2.0: setting rx_max = 16384
[785963.017169] cdc_ncm 1-1:2.0: setting tx_max = 16384
[785963.017682] cdc_ncm 1-1:2.0 usb0: register 'cdc_ncm' at usb-0000:00:14.0-1, CDC NCM, 00:24:27:88:08:15
[785963.019211] usbcore: registered new interface driver cdc_ncm
[785963.023856] usbcore: registered new interface driver cdc_wdm
[785963.025461] usbcore: registered new interface driver cdc_mbim
[785963.038824] cdc_ncm 1-1:2.0 enx002427880815: renamed from usb0
[785963.089586] cdc_ncm 1-1:2.0 enx002427880815: network connection: disconnected
[785963.121673] cdc_ncm 1-1:2.0 enx002427880815: network connection: disconnected
[785963.153682] cdc_ncm 1-1:2.0 enx002427880815: network connection: disconnected
...

This is about 2KB per second and will overwrite all contents of a 1MB
dmesg buffer in under 10 minutes rendering them useless for debugging
many kernel problems.

This is also an extra 180 MB/day in /var/logs (or 1GB per week) rendering
the majority of those logs useless too.

When the link is up (expected state), spew amount is >2x higher:
...
[786139.600992] cdc_ncm 2-1:2.0 enx002427880815: network connection: connected
[786139.632997] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink 2500 mbit/s uplink
[786139.665097] cdc_ncm 2-1:2.0 enx002427880815: network connection: connected
[786139.697100] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink 2500 mbit/s uplink
[786139.729094] cdc_ncm 2-1:2.0 enx002427880815: network connection: connected
[786139.761108] cdc_ncm 2-1:2.0 enx002427880815: 2500 mbit/s downlink 2500 mbit/s uplink
...

Chrome OS cannot support RTL8156 until this is fixed.

Signed-off-by: Grant Grundler <grundler@chromium.org>
Reviewed-by: Hayes Wang <hayeswang@realtek.com>
Link: https://lore.kernel.org/r/20210120011208.3768105-1-grundler@chromium.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 5a78848..291e76d 100644 (file)
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1827,6 +1827,15 @@ cdc_ncm_speed_change(struct usbnet *dev,
        uint32_t rx_speed = le32_to_cpu(data->DLBitRRate);
        uint32_t tx_speed = le32_to_cpu(data->ULBitRate);
 
+       /* if the speed hasn't changed, don't report it.
+        * RTL8156 shipped before 2021 sends notification about every 32ms.
+        */
+       if (dev->rx_speed == rx_speed && dev->tx_speed == tx_speed)
+               return;
+
+       dev->rx_speed = rx_speed;
+       dev->tx_speed = tx_speed;
+
        /*
         * Currently the USB-NET API does not support reporting the actual
         * device speed. Do print it instead.
@@ -1867,7 +1876,8 @@ static void cdc_ncm_status(struct usbnet *dev, struct urb *urb)
                 * USB_CDC_NOTIFY_NETWORK_CONNECTION notification shall be
                 * sent by device after USB_CDC_NOTIFY_SPEED_CHANGE.
                 */
-               usbnet_link_change(dev, !!event->wValue, 0);
+               if (netif_carrier_ok(dev->net) != !!event->wValue)
+                       usbnet_link_change(dev, !!event->wValue, 0);
                break;
 
        case USB_CDC_NOTIFY_SPEED_CHANGE:

diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 88a7673..cfbfd6f 100644 (file)
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -81,6 +81,8 @@ struct usbnet {
 #              define EVENT_LINK_CHANGE        11
 #              define EVENT_SET_RX_MODE        12
 #              define EVENT_NO_IP_ALIGN        13
+       u32                     rx_speed;       /* in bps - NOT Mbps */
+       u32                     tx_speed;       /* in bps - NOT Mbps */
 };
 
 static inline struct usb_driver *driver_of(struct usb_interface *intf)