[PATCH 4.9 01/29] net: usb: cdc_ncm: dont spew notifications

Greg Kroah-Hartman
2021-06-08T18:30:00Z

From: Grant Grundler <grundler@chromium.org>

[ Upstream commit de658a195ee23ca6aaffe197d1d2ea040beea0a2 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/usb/cdc_ncm.c | 12 +++++++++++-
include/linux/usb/usbnet.h | 2 ++
2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index d418542924e1..297d3f599efd 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1563,6 +1563,15 @@ 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.
@@ -1606,7 +1615,8 @@ 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 fde7550754df..52f47c2944f8 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -80,6 +80,8 @@ 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)
--
2.30.2