Date:	Wed, 31 Jul 2013 11:11:45 +0200
From:	Jeroen Koekkoek <jeroen@...kkoek.nl>
To:	linux-kernel@...r.kernel.org
Cc:	Michael Hunold <hunold@...uxtv.org>
Subject: Re: Link state change detection problem on Moschip MCS7832 again

On Fri, 2013-01-11 at 11:15 +0100, Michael Hunold wrote:
> Hi,
> 
> I have a no-name Moschip MCS7832-based adapter shows a strange behaviour 
> in my system after a system upgrade. "lsusb -vv" for that device is 
> attached to the end of the mail.
> 
> I am using the adapter for embedded systems development, where it serves 
> kernels via TFTP and root filesystems via NFS.
> 
> I have recently upgrade my system to Kubuntu 12.10 which uses a 3.5.0-21 
> kernel. Before that upgrade the device was working fine with Xubuntu 10.10.
> 
> I have used the network-manager applet that comes with Kubuntu to assign 
> a static IP address to that interface.
> 
> The symptom is that when the remote system's bootloader (u-boot in my 
> case) starts to fetch the kernel via TFTP, it usually starts fine (a 
> couple of "#" are shown to indicate progress), then timeouts are 
> happening ("T" is shown), then progress continues, then more timeouts 
> and so on.
> 
> I can see the following messages getting repeated in /var/log/syslog:
> 
> [...]
> Jan 11 11:01:04 elmc-teemhu NetworkManager[1250]: <info> (eth1): carrier 
> now OFF (device state 100, deferring action for 4 seconds)
> Jan 11 11:01:04 elmc-teemhu NetworkManager[1250]: <info> (eth1): carrier 
> now ON (device state 100)
> [...]
> 
> I found the following bug report and this got me going:
> https://bugzilla.kernel.org/show_bug.cgi?id=28532
> 
> Here is what I investigated so far.
> 
> 1. I noticed that the patch dabdaf0caa3af520dbc1df87b2fb4e77224037bd 
> from Ondrej Zary is missing in the kernel Kubuntu is serving, so I 
> downloaded the most-recent mcs7830.c from kernel.org and recompiled the 
> module. The problem stays the same, there is no improvement.
> 
> 2. I undid both commits dabdaf0caa3af520dbc1df87b2fb4e77224037bd and 
> b1ff4f96fd1c63890d78d8939c6e0f2b44ce3113 which added the "mcs7830: 
> Implement link state detection" in the first place. Without that 
> "feature" my adapter is now working reliably again.
> 
> 3. Commit dabdaf0caa3af520dbc1df87b2fb4e77224037bd had the following 
> comment:
> 
> "The device had an undocumented "feature": it can provide a sequence of
> spurious link-down status data even if the link is up all the time.
> A sequence of 10 was seen so update the link state only after the device
> reports the same link state 20 times."
> 
> I tried to increase the number from 20 gradually, but it did not help to 
> fix the problem. In my desparation I tried 100 as well, but this only 
> postponed the
> 
> 4. In my desparation, I went back to the most recent driver and added 
> the following code to mcs7830_status() in order to track after how many 
> calls to that function the link state changes.
> 
> [...]
> {
> 	static int xxx_counter = 0;
> 	static int xxx_link = -1;
> 	if (link != xxx_link) {
> 		printk("counter %4d -> link %d\n", xxx_counter, link);
> 		xxx_link = link;
> 		xxx_counter = 0;
> 	} else {
> 		xxx_counter++;
> 	}
> }
> [...]
> 
> This resulted in the following output:
> 
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.025109] counter  105 -> link 0
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.101840] counter   76 -> link 1
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.207724] counter  105 -> link 0
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.285582] counter   77 -> link 1
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.392416] counter  106 -> link 0
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.468149] counter   75 -> link 1
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.574036] counter  105 -> link 0
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.651893] counter   77 -> link 1
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.757719] counter  105 -> link 0
> Jan 11 11:01:04 elmc-teemhu NetworkManager[1250]: <info> (eth1): carrier 
> now OFF (device state 100, deferring action for 4 seconds)
> Jan 11 11:01:04 elmc-teemhu kernel: [11627.834546] counter   76 -> link 1
> Jan 11 11:01:04 elmc-teemhu NetworkManager[1250]: <info> (eth1): carrier 
> now ON (device state 100)
> Jan 11 11:01:05 elmc-teemhu kernel: [11627.939259] counter  104 -> link 0
> Jan 11 11:01:05 elmc-teemhu kernel: [11628.018204] counter   78 -> link 1
> 
> So it seems the link state is constantly toggling and the network 
> manager eventually picks that up and does some reconfiguratation to the 
> network interface which disturbs both TFTP and NFS.
> 
> As I already said above, when I undo both commits then everything is 
> working fine again. Network manager is not complaining any more and TFTP 
> and NFS is working fine.
> 
> Any idea what is wrong with that adapter? Is it unable to report link 
> state changes correctly at all?
> 
> How to make the current driver work correctly without reverting the two 
> commit completly?
> 
> Best regards
> Michael.

Hi,

I'm experiencing the same problem. After reverting the commits below, my
problems disappeared.

commit b1ff4f96fd1c63890d78d8939c6e0f2b44ce3113
	mcs7830: Implement link state detection

commit b1ff4f96fd1c63890d78d8939c6e0f2b44ce3113
	mcs7830: Implement link state detection

I'm running Fedora 19 (Linux laptop.lan 3.10.3-300.fc19.x86_64 #1 SMP
Fri Jul 26 00:00:58 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux).

Best regards,
Jeroen Koekkoek

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