[SeaBIOS] Long delay: WARNING - Timeout at wait_reg8:81!

[Paul Menzel]

Dear Stephen,


On 03/07/2018 07:24 PM, Stephen Douthit wrote:
> On 03/07/2018 12:41 PM, Kevin O'Connor wrote:
>> On Wed, Mar 07, 2018 at 12:33:36PM -0500, Stephen Douthit wrote:
>>> On 03/07/2018 10:33 AM, Paul Menzel wrote:

>>>> Am Dienstag, den 06.03.2018, 11:57 -0500 schrieb Stephen Douthit:
>>>>> On 03/06/2018 11:04 AM, Paul Menzel wrote:
>>>>>> On 03/02/18 17:31, Kevin O'Connor wrote:
>>>>>>>
>>>>>>> On Tue, Feb 27, 2018 at 02:17:08PM -0500, Stephen Douthit wrote:
>>>>>> […]
>>>>>>
>>>>>>>
>>>>>>> Thanks.  I committed this series.
>>>>>> The second commit introduced a regression with coreboot on the
>>>>>> ASRock E350M1. There are a bunch of time-outs, causing the startup
>>>>>> to be really slow. With no serial console, the user thinks, it’s
>>>>>> not working and start to debug.
>>>>>
>>>>> Looking through the the user manual for that board I don't see that it
>>>>> has a TPM, or even the header for one, so a timeout seems correct.
>>>>
>>>> Indeed, no TPM is present.
>>>
>>> Thanks for confirming.
>>>
>>>>> Multiple 750ms timeouts does seem pretty painful though.  I hadn't
>>>>> considered that tis_probe() would be called multiple times if no TPM
>>>>> was present.
>>>>>
>>>>> What's the preferred way to have a probe function run and bail before
>>>>> rerunning the timeout?  Just put a static flag in tis_probe()?  The
>>>>> attached patch takes that approach.  Please let me know if that fixes
>>>>> the issue for you, or if there's some other preferred pattern I should
>>>>> use here.
>>>>
>>>> Unfortunately, that didn’t help.
>>>>
>>>> ```
>>>> $ git log --oneline -2
>>>> fd1cbb4 (HEAD -> master, origin/master, origin/HEAD) tpm: Save 
>>>> tis_probe() result to avoid a reun of lengthy timeouts
>>>> 5adc8bd tpm: Handle unimplemented TIS_REG_IFACE_ID in 
>>>> tis_get_tpm_version()
>>>> ```
>>>>
>>>> And the time-outs seem to be around 20 seconds or more. Please find the
>>>> log with time stamps attached (`sudo ./readserial.py /dev/ttyUSB0`).
>>>
>>> Yikes, 20 seconds is the medium duration timeout, not the default A
>>> timeout of 750ms.  I was poking the wrong area with the last patch.
>>> It looks like tis_probe() is propagating the return from
>>> tis_wait_access() in the no device present case.
>>
>> FYI, even adding 5ms to the boot time is unacceptable.  Is there
>> anyway to verify the hardware exists before waiting for it to be
>> ready?
> 
> The only way I know of would be to check if we have TCPA or TPM2 ACPI
> tables, and only attempt to probe for a TPM if those are present.
> 
> Attached patch should do that, and it's probably a good idea
> independent of any of my other patches.

I applied both the latest commits, and quickly testing that, I believe 
the long delay is still there. I won’t be able to get to until next 
week, and make the ACPI tables available. Maybe there is a way to test 
this with QEMU? Kevin also owns the ASRock E350M1 to my knowledge.


Kind regards,

Paul