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

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Date:   Wed, 20 Dec 2017 19:33:26 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     "Shaikh, Azhar" <azhar.shaikh@...el.com>,
        "Alexander.Steffen@...ineon.com" <Alexander.Steffen@...ineon.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "james@...le.org.uk" <james@...le.org.uk>,
        "arnd@...db.de" <arnd@...db.de>,
        "jarkko.sakkinen@...ux.intel.com" <jarkko.sakkinen@...ux.intel.com>,
        "peterhuewe@....de" <peterhuewe@....de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>
Subject: Re: [PATCH 0/4] tpm: fix PS/2 devices not working on Braswell systems
 due CLKRUN enabled

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