linux-kernel - Re: [tpmdd-devel] [PATCH] TPM: Work around buggy TPMs that block during continue self test

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Date:	Fri, 25 Jan 2013 13:25:38 -0700
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Kent Yoder <shpedoikal@...il.com>
Cc:	linux-kernel@...r.kernel.org, tpmdd-devel@...ts.sourceforge.net
Subject: Re: [tpmdd-devel] [PATCH] TPM: Work around buggy TPMs that block
 during continue self test

On Tue, Jan 22, 2013 at 05:29:23PM -0600, Kent Yoder wrote:
> Hi Jason,
> 
> On Wed, Nov 21, 2012 at 3:15 PM, Jason Gunthorpe
> <jgunthorpe@...idianresearch.com> wrote:
> > We've been testing an alternative TPM for our embedded products and
> > found random kernel boot failures due to time outs after the continue
> > self test command.
> >
> > This was happening randomly, and has been *very* hard to track down, but it
> > looks like with this chip there is some kind of race with the tpm_tis_status()
> > check of TPM_STS_COMMAND_READY. If things get there 'too fast' then
> > it sees the chip is ready, or tpm_tis_ready() works. Otherwise it takes
> > somewhere over 400ms before the chip will return TPM_STS_COMMAND_READY.
> >
> > Adding some delay after tpm_continue_selftest() makes things reliably
> > hit the failure path, otherwise it is a crapshot.
> 
>   I've staged this patch here, please test:
> 
> https://github.com/shpedoikal/linux.git tpmdd-01-22-13

Thanks Kent, I will try to test your branch next week, if I am able.

Can you also grab

https://github.com/jgunthorpe/linux/commit/98b2a198b43b41b0535200bf475160786398f114

And did you have any comments on:

https://github.com/jgunthorpe/linux/commit/9981e3e622bf702394982117134bed731ffd6f7e

Both were posted to the list a bit ago.

Regards,
-- 
Jason Gunthorpe <jgunthorpe@...idianresearch.com>        (780)4406067x832
Chief Technology Officer, Obsidian Research Corp         Edmonton, Canada
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