Re: [PATCH 0/4] tpm: fix PS/2 devices not working on Braswell systems due CLKRUN enabled

From: Javier Martinez Canillas
Date: Wed Dec 20 2017 - 13:33:37 EST

On 12/20/2017 06:44 PM, Jason Gunthorpe wrote:
> On Wed, Dec 20, 2017 at 05:45:16PM +0100, Javier Martinez Canillas wrote:
>> CHP51 says "LPC Clock Control Using the LPC_CLKRUN# May Not Behave As Expected"
>> and that the implication is that "The SoC may prevent a peripheral device from
>> successfully requesting the LPC clock".
> Now we are back to the beginning - the LPC_CLKRUN protocol is simply
> broken in BSW chipsets, and it has nothing to do with the TPM?
> Intel is trying to work around that broken-ness and still preserve
> power management in the case where only the TPM is connected to the
> LPC bus.. It is questionable to me if this is even a good idea, or if
> Linux is the right place to implement this work around (eg something
> in SMM mode may be more appropriate for a chipset bug)
> I think your patch is still the right improvement, if the BIOS turned
> the feature off, we should not turn it back on.

Yes, the patch has merits on its own since fixes a flaw in the logic of
the original CLKRUN patch. I think we should merge it and then the other
issues can be fixed (or rework how the CLKRUN is managed) as follow-ups.

> Jason

Best regards,
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat