Re: (2nd try) [PATCH] corruption during e100 MDI register access

On 1/6/06, ODonnell, Michael [off-list ref] wrote:

 [ 2nd transmission.  Microsoft mailer "helpfully"
  reformatted the patch in the last one... :-(    ]

Greetings,

We have identified two related bugs in the e100 driver and we request
that they be repaired in the official Intel version of the driver.

Both bugs are related to manipulation of the MDI control register.

The first problem is that the Ready bit is being ignored when
writing to the Control register; we noticed this because the Linux
bonding driver would occasionally come to the spurious conclusion
that the link was down when querying Link State.  It turned out
that by failing to wait for a previous command to complete it was
selecting what was essentially a random register in the MDI register
set.  When we added code that waits for the Ready bit (as shown in
the patch file below) all such problems ceased.

damn, you know I had seen this on one machine only, and the machine
had other problems, so i thought it wasn't e100.  I can't quite figure
out why we haven't seen this more often given how long the bug appears
to have existed.

The second problem is that, although access to the MDI registers
involves multiple steps which must not be intermixed, nothing was
defending against two or more threads attempting simultaneous access.
The most obvious situation where such interference could occur
involves the watchdog versus ioctl paths, but there are probably
others, so we recommend the locking shown in our patch file.

Agreed, but once again I am simply amazed this has been there so long.

I think these are both good patches and I'll ack this and absorb it
for our next release.  It will be a bit before its completely through
our process but its okay with me if this goes into the kernel now.

Jesse