Re: [PATCH] tpm.h: increase poll timings to fix tpm_tis regression

Jason Gunthorpe
2018-07-11T21:12:57Z

On Wed, Jul 11, 2018 at 10:51:40PM +0200, Peter Huewe wrote:
>
>
> Am 11. Juli 2018 22:39:05 MESZ schrieb James Bottomley <James.Bottomley@HansenPartnership.com>:
> >On Wed, 2018-07-11 at 14:01 -0600, Jason Gunthorpe wrote:
> >> On Wed, Jul 11, 2018 at 12:08:53PM -0700, James Bottomley wrote:
> >> > On Wed, 2018-07-11 at 12:21 -0600, Jason Gunthorpe wrote:
> >> > > On Wed, Jul 11, 2018 at 10:11:14AM -0700, James Bottomley wrote:
> >> > > > tpm_tis regressed recently to the point where the TPM being
> >> > > > driven
> >> > > > by
> >> > > > it falls off the bus and cannot be contacted after some hours
> >> > > > of
> >> > > > use.
> >> > > > This is the failure trace:
> >> > > >
> >> > > > jejb@jarvis:~> dmesg|grep tpm
> >> > > > [ 3.282605] tpm_tis MSFT0101:00: 2.0 TPM (device-id 0xFE,
> >> > > > rev-id
> >> > > > 2)
> >> > > > [14566.626614] tpm tpm0: Operation Timed out
> >> > > > [14566.626621] tpm tpm0: tpm2_load_context: failed with a
> >> > > > system
> >> > > > error -62
> >> > > > [14568.626607] tpm tpm0: tpm_try_transmit: tpm_send: error -62
> >> > > > [14570.626594] tpm tpm0: tpm_try_transmit: tpm_send: error -62
> >> > > > [14570.626605] tpm tpm0: tpm2_load_context: failed with a
> >> > > > system
> >> > > > error -62
> >> > > > [14572.626526] tpm tpm0: tpm_try_transmit: tpm_send: error -62
> >> > > > [14577.710441] tpm tpm0: tpm_try_transmit: tpm_send: error -62
> >> > > > ...
> >> > > >
> >> > > > The problem is caused by a change that caused us to poke the
> >> > > > TPM
> >> > > > far
> >> > > > more often to see if it's ready. Apparently something about
> >> > > > the
> >> > > > bus
> >> > > > its on and the TPM means that it crashes or falls off the bus
> >> > > > if
> >> > > > you
> >> > > > poke it too often and once this happens, only a reboot will
> >> > > > recover
> >> > > > it.
> >> > >
> >> > > I wonder if something about triggering ETIME even once breaks the
> >> > > driver so it can't talk to the chip at all thereafter..
> >> > >
> >> > > Ie it doesn't abort the command properly and becomes desynced
> >> > > with the TIS execution protocol.
> >> >
> >> > Yes, I wondered about this, but I don't understand the bus protocol
> >> > well enough. The tpm-interface:tpm_try_transmit() which throws the
> >> > first ETIME says after we get that we send chip->ops->cancel()
> >> > which tpm_tis simply translates to tpm_tis_ready() which also times
> >> > out. Is there a bigger hammer I can hit it with?
> >>
> >> I don't remember off hand.. But this is, IMHO, a better guess than
> >> the firmware crashes from reading the status register..
> >
> >Oh, actually, I think the bus crashes or wedges, not the TPM. I just
> >don't have any tools to probe the LPC.
> >
>
> I doubt that your fTPM is actually attached to LPC.
> And usually if lpc wedges it takes down your pc with it (from my experience)

Yes, agree. Very, very unlikely LPC crashed or wedged.

You could try reading the ID numbers register (eg the source of this
data 'device-id 0xFE rev-id 2').

That should be on the HW side of the FIFO bridge and if it returs the
same values as boot the bus is not broken, no matter what the bus is.

Jason