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

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Message-ID: <20171220174400.GA22908@ziepe.ca>
Date:   Wed, 20 Dec 2017 10:44:00 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Javier Martinez Canillas <javierm@...hat.com>
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 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.

Jason