[SeaBIOS] [PATCH v1 2/3] tpm: Wait for interface startup when probing

[Kevin O'Connor]

On Fri, Mar 02, 2018 at 11:27:46AM -0500, Stephen Douthit wrote:
> On 03/02/2018 11:05 AM, Kevin O'Connor wrote:
> > On Tue, Feb 27, 2018 at 02:17:10PM -0500, Stephen Douthit wrote:
> > > This is based on wait_startup() from the Linux tpm_tis driver.
> > > 
> > > Signed-off-by: Stephen Douthit <stephend at silicom-usa.com>
> > > Tested-by: Stephen Douthit <stephend at silicom-usa.com>
> > > ---
> > >   src/hw/tpm_drivers.c | 13 ++++++++++++-
> > >   1 file changed, 12 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/src/hw/tpm_drivers.c b/src/hw/tpm_drivers.c
> > > index 13ad821..da8bb63 100644
> > > --- a/src/hw/tpm_drivers.c
> > > +++ b/src/hw/tpm_drivers.c
> > > @@ -86,6 +86,11 @@ static u32 wait_reg8(u8* reg, u32 time, u8 mask, u8 expect)
> > >       return rc;
> > >   }
> > > +static u32 tis_wait_access(u8 locty, u32 time, u8 mask, u8 expect)
> > > +{
> > > +    return wait_reg8(TIS_REG(locty, TIS_REG_ACCESS), time, mask, expect);
> > > +}
> > > +
> > >   static u32 tis_wait_sts(u8 locty, u32 time, u8 mask, u8 expect)
> > >   {
> > >       return wait_reg8(TIS_REG(locty, TIS_REG_STS), time, mask, expect);
> > > @@ -102,7 +107,13 @@ static u32 tis_probe(void)
> > >       if (!CONFIG_TCGBIOS)
> > >           return 0;
> > > -    u32 rc = 0;
> > > +    /* Wait for the interface to report it's ready */
> > > +    u32 rc = tis_wait_access(0, TIS_DEFAULT_TIMEOUT_A,
> > > +                             TIS_ACCESS_TPM_REG_VALID_STS,
> > > +                             TIS_ACCESS_TPM_REG_VALID_STS);
> > > +    if (rc)
> > > +        return 0;
> > > +
> > 
> > Thanks.  I was about to commit this when I noticed the above.  In the
> > case where tis_wait_access() fails due to a timeout, shouldn't
> > tis_probe() return an error indicator instead of success?
> 
> tis_probe() returns 0 for no device, '1' for device present.
> 
> Take a look at the usage in tpmhw_probe(), or the comment on
> tis_probe() itself.

Okay, thanks for clarifying.

-Kevin