Re: [PATCH 2/2] tpm: tpm_crb: enhance resource mapping mechanism for supporting AMD's fTPM

[Seunghun Han]

>
> On Fri, Aug 30, 2019 at 10:54:59PM +0900, Seunghun Han wrote:
>
> > When I tested this patch in my machine, it seemed that ACPI NVS was
> > saved after TPM CRB driver sent "TPM2_Shutdown(STATE)" to the fTPM
> > while suspending. Then, ACPI NVS was restored while resuming.
> > After resuming, PCRs didn't change and TPM2 tools such as
> > tpm2_pcrlist, tpm2_extend, tpm2_getrandoms worked well.
> > So, according to my test result, it seems that the patch doesn't
> > create bugs and race during resume.
>
> I have a feeling that is shear luck of link time ordering and not guarenteed??
>
> Jason

No, it is guaranteed. As you know, suspend_nvs_save() is called by
acpi_pm_pre_suspend(), and it is called by
platform_suspend_prepare_noirq(). platform_suspend_prepare_noirq() is
also called by suspend_enter(), and it already suspends all devices
like TPM CRB driver before calling platform_suspend_prepare_noirq().
This means that the order is guaranteed and we don't need to worry about it.

Seunghun