On Thu, Apr 16, 2020 at 08:22:10AM +0200, Paul Menzel wrote:
> Dear Omar,
>
>
> Am 16.04.20 um 02:23 schrieb Omar Sandoval:
> > From: Omar Sandoval <osandov@xxxxxx>
>
> Thank you for the patch.
>
> > We've encountered a particular model of STMicroelectronics TPM that
>
> Please add models you are encountering this with to the commit message.
>
> > transiently returns a bad value in the status register. This causes the
>
> Have you contacted STMMicroelectronics?
>
> > kernel to believe that the TPM is ready to receive a command when it
> > actually isn't, which in turn causes the send to time out in
> > get_burstcount(). In testing, reading the status register one extra time
> > convinces the TPM to return a valid value.
> >
> > Signed-off-by: Omar Sandoval <osandov@xxxxxx>
> > ---
> > drivers/char/tpm/tpm_tis_core.c | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> >
> > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > index 27c6ca031e23..5a2f6acaf768 100644
> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -238,6 +238,25 @@ static u8 tpm_tis_status(struct tpm_chip *chip)
> > rc = tpm_tis_read8(priv, TPM_STS(priv->locality), &status);
> > if (rc < 0)
> > return 0;
> > + /*
> > + * Some STMicroelectronics TPMs have a bug where the status register is
> > + * sometimes bogus (all 1s) if read immediately after the access
> > + * register is written to. Bits 0, 1, and 5 are always supposed to read
> > + * as 0, so this is clearly invalid. Reading the register a second time
> > + * returns a valid value.
> > + */
> > + if (unlikely(status == 0xff)) {
>
> I’d like to see a debug message here, saying the TPM is buggy. Maybe the
> model can be printed to, and that the TPM manufacturer should be contacted.
How can I get the model information? (Sorry, I'm not very familiar with
TPMs, I'm just the guy on the team that ended up tracking this down.)
Thanks!
