Re: [PATCH] Fix Atmel TPM crash caused by too frequent queries

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Sun, Sep 27, 2020 at 11:25:39AM -0700, James Bottomley wrote:
> On Sat, 2020-09-26 at 16:10 -0700, Hao Wu wrote:
> > Resending following email in plaintext.
> > 
> > ----
> > 
> > Hi James,
> > 
> > Thanks for following up.
> > 
> > We have actually tried change 
> > TPM_TIMEOUT_USECS_MIN / TPM_TIMEOUT_USECS_MAX 
> > according to https://patchwork.kernel.org/patch/10520247/
> > It does not solve the problem for ATMEL chip. The chips facing crash
> > is 
> > not experimental, but happens commonly in 
> > the production systems we and our customers are using.
> > It is widely found in Cisco 220 / 240 systems which are using
> > Ateml chips.
> 
> Well, I came up with the values in that patch by trial and error ....
> all I know is they work for my nuvoton. If they're not right for you,
> see if you can find what values actually do work for your TPM.  The
> difference between msleep and usleep_range is that the former can have
> an indefinitely long timeout and the latter has a range bounded one. 
> If you think msleep works for you, the chances are it doesn't and
> you're relying on the large upper bound to make the bug infrequent
> enough for you not to see it.  Playing with the values in usleep range
> will help you find what the actual timeout is and eliminate the problem
> for good.
> 
> James

I think I should revert 424eaf910c329, up until more legit values are found.

/Jarkko