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

[Stephen Douthit]

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.

Thanks,
Steve