Re: Contacts within AMD? AMD-756 USB host-controller blacklisted due to

[Miles Lane]

Thomas Dodd wrote:

> Alan Cox wrote:
> 
>>> David Brownell recently added this check to the usb-ohci driver
>>> since noone has gotten information from AMD for the workaround,
>>> which is rumored to exist, for this bug.
>>> 
>>> Do any of you have contacts within AMD who might be able to
>>> get an explanation of the workaround to David Brownell?
>> 
>> We are working on that currently via the Red Hat contact.
>> 
>> 
>>> value given varies.  Rereading NDP seems to give a valid value.
>>> I am not really clear why we don't simply read the value twice
>>> whenever the host-controller is detected to be an AMD-756.
>> 
>> because we dont know the full scope of the problem yet.
> 
> 
> Exactly how many bug reports has this caused?
> What kind of problems?
> 
> I know I had trouble onece, but it was a CONFIG problem
> with the 2.4.2ac series and the extra DEBUG options.

I think probably everyone who has an AMD-756 has reported
this error.  At least, I've not seen any messages from
people saying, "I have an AMD-756 and have never seen this
error."  Most of the time, when the error occurs, it seems
pretty benign.  That is, I haven't noticed it crashing USB
device connections, causing data corruption or OOPSen.
Some folks _have_ reported OOPSen, though, that seemed to
be triggered by the erratum #4 hardware bug.  I think I
may have had one of these a long time ago.

I believe David has found that there definitely are code
paths where this hardware bug can cause failures of various
sorts and that's why the AMD-756 has been blacklisted.
I don't believe these failure code paths have anything to
do with specific debugging configurations.

David/Alan, please correct me if I've got this all wrong.

Thanks,
	Miles