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Date:   Wed, 20 Dec 2017 10:44:00 -0700
From:   Jason Gunthorpe <>
To:     Javier Martinez Canillas <>
Cc:     "Shaikh, Azhar" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>
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.


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