Re: [BUG] bisected: PandaBoard smsc95xx ethernet driver error fromUSB timeout

From: Frank Rowand
Date: Thu Mar 21 2013 - 16:26:38 EST

On 03/21/13 02:00, Ming Lei wrote:
> Hi Frank,
> On Thu, Mar 21, 2013 at 11:29 AM, Frank Rowand <frank.rowand@xxxxxxxxxxx> wrote:
>> I found the problem on 3.6.11, but have not replicated it on 3.9-rcX
>> yet because my config fails to build on 3.9-rc1 and 3.9-rc2. I'll try
>> to work on that issue tomorrow.
> I play upstream kernel on Pandaboard A1 frequently, looks not
> see the failure problem before. Maybe the problem is config dependent.
> If you may share your config file, I'd like to do the test too.

I will do a separate reply with the actual config at the point where
the bisect completed.

I create the config for each commit during the bisect with scripts
that do the equivalent of:

make omap2plus_defconfig

make menuconfig

# this allows USB thumb drive
# Device Drivers -> USB support -> EHCI HCD (USB 2.0) support

# ethernet device
# Device Drivers -> Network device support -> USB Network Adapters ->
# Multi-purpose USB Networking Framework ->
# SMSC LAN95XX based USB 2.0 10/100 ethernet devices

Some more random information that may be helpful....

$ cat /proc/cmdline
ip= nfsroot= root=/dev/nfs ip=dhcp mem=463M console=ttyO2,115200n8 debug earlyprintk

The percentage of boots that show the problem varies quite a bit between
the kernel versions that I tried during my bisect. For my first attempt
at bisecting, I decided a version was good if it booted 12 times. That
bisect failed for various reasons. For my second attempt at bisecting,
I decided a version was good if it booted 18 times.

There are some timeout messages that I am not positive are symptoms of
the problem. With these messages, the smsc95xx driver initialization is
successful, so the ethernet device is available. For the first bisect
attempt, I did not treat these messages as errors. For the second bisect
attempt I treated these messages as errors. A typical example of the
timeout message is:

[ 9.537811] hub 1-1:1.0: state 7 ports 5 chg 0000 evt 0002
[ 17.056701] usb 1-1.1: swapper/0 timed out on ep0out len=0/4
[ 17.062652] smsc95xx 1-1.1:1.0: eth0: Failed to write register index 0x00000108
[ 17.070343] smsc95xx 1-1.1:1.0: eth0: Failed to write ADDRL: -110
[ 17.076751] IP-Config: Failed to open eth0

The mention of swapper is not relevent, it just happens to be the
current process when the time out occurs.

I have only seen these timeout messages in the boot log, so they may not
be a very visible symptom. They also _might_ be unrelated to the problem,
but my gut feel is that they are related.

The problem manifests as a timeout from at least two different locations
in drivers/net/usb/smsc95xx.c:

656 static int smsc95xx_set_mac_address(struct usbnet *dev)
657 {
663 ret = smsc95xx_write_reg(dev, ADDRL, addr_lo);
664 if (ret < 0) {
665 netdev_warn(dev->net, "Failed to write ADDRL: %d\n", ret);
666 return ret;
667 }

751 static int smsc95xx_reset(struct usbnet *dev)
752 {
783 write_buf = PM_CTL_PHY_RST_;
784 ret = smsc95xx_write_reg(dev, PM_CTRL, write_buf);
785 if (ret < 0) {
786 netdev_warn(dev->net, "Failed to write PM_CTRL: %d\n", ret);
787 return ret;
788 }

There may be additional locations. These are just two that I captured when
debugging. Some of the other smsc95xx_write_reg() calls in smsc95xx_reset()
are protected with checks for timeout, with up to 100 retries. I don't know
if more checks for timeout, or longer timeout, is a solution or just an
incorrect way of papering over the real problem -- this is not an area of
expertise for me.



To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at