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Date:   Mon, 18 Dec 2017 19:08:00 -0700
From:   Jason Gunthorpe <>
To:     Javier Martinez Canillas <>
Cc:     "Shaikh, Azhar" <>,
        Jarkko Sakkinen <>,
        James Ettle <>,
        "" <>,
        "" <>,
        "" <>
Subject: Re: [BISECTED] tpm CLKRUN breaks PS/2 keyboard and touchpad on
 Braswell system

On Tue, Dec 19, 2017 at 12:34:46AM +0100, Javier Martinez Canillas wrote:
> Hello Jason,
> On 12/18/2017 09:19 PM, Jason Gunthorpe wrote:
> > On Mon, Dec 18, 2017 at 07:34:29PM +0000, Shaikh, Azhar wrote:
> > 
> >>> IIUC, if CLKRUN_EN is enabled, then all the devices attached to the
> >>> LPC bus have to support the CLKRUN protocol. My guess is that on
> >>> some Braswell systems LPC power management is enabled but the TPM
> >>> device doesn't have CLKRUN support.
> >>
> >> I think this is what might be happening here.
> > 
> > That makes it a BIOS bug, not a chipset bug, and we shouldn't be
> > trying to fix it like this in Linux.
> >
> Indeed, the system integrator should make sure that all peripherals that
> are connected through the LPC bus either support the CLKRUN protocol and
> CLKRUN_EN is enabled or CLKRUN_EN should be disabled.

I would like to hear from Intel why they made this patch in the first
place, since we are mostly guessing...

> 1) Leave the code as is and apply the patch I shared with James. In that
>    case the CLKRUN protocol will be disabled only during TPM transactions
>    and not enabled again after transactions if it wasn't enabled.

This seems necessary no matter what, especially if it works..

> 2) Drop the pending CLKRUN patch in linux-tpmdd and revert CLKRUN commit
>    in mainline. And instead of disabling the CLKRUN protocol during the
>    TPM transactions, disable if the CLKRUN_EN is enabled and the system
>    is in a list of systems that have a TPM that doesn't support CLKRUN.

This is also a good possible idea.

Again, depends why Intel did this. I assumed it was a chipset bug
since Intel was sending it not a system builder..


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