Re: [BISECTED] tpm CLKRUN breaks PS/2 keyboard and touchpad on Braswell system

Javier Martinez Canillas
2017-12-12T11:38:03Z

Hello James,

On 12/11/2017 08:37 PM, James Ettle wrote:
> Hello,
>
> [First: Apologies if cross-posting from Kernel.org BZ is bad form; my distro BZ advised I post this to your mailing list as well.]
>
> Situation: enabling TPM on a Clevo W510LU with an Intel N3160 CPU breaks PS/2 keyboard and mouse. They just don't respond until after a suspend/resume cycle, and after that they later stop after a while.
>
> I have confirmed this by blacklisting tpm modules. I noticed this first with kernel 4.13, and have bisected it down to:
>
> 5e572cab92f0bb56ca1e6e5ee4d807663a7ccbad is the first bad commit
> commit 5e572cab92f0bb56ca1e6e5ee4d807663a7ccbad
> Author: Azhar Shaikh <azhar.shaikh@intel.com>
> Date: Sun Jun 18 19:17:59 2017 -0700
>
> tpm: Enable CLKRUN protocol for Braswell systems
>
> To overcome a hardware limitation on Intel Braswell systems,
> disable CLKRUN protocol during TPM transactions and re-enable
> once the transaction is completed.
>
> Signed-off-by: Azhar Shaikh <azhar.shaikh@intel.com>
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Signed-off-by: James Morris <james.l.morris@oracle.com>
>
> :040000 040000 5437c91886cb62c497255f2c60dbedd7268ab50d 1863a1738ded35a817aad52f9f2b451bd43623d7 M drivers
>
> Currently in Kernel.org bugzilla 197287.
>
> Please let me know if you need any further info.
>

I don't have access to a Braswell machine to reproduce this. I tried to do it
on different Intel systems by modifying is_bsw() to always return true, but
that didn't work either. They work correctly even when CLKRUN_EN is toggled.

I'm not familiar with LPC so please let me know if my assumptions are wrong,
but I find suspicious that a driver for a single device attached to the bus
can control the CLKRUN# signal which AFAIU may be needed for other devices.

So that would explain why the mentioned commit causes issues for PS/2 mouse
and keyboards, since these are attached to the LPC bus and may rely on the
CLKRUN# signal for proper operation.

I see that the following [0,1] patches for the tpm_tis driver landed a few
days ago, they change how the CLKRUN protocol is enabled/disabled. Instead
of doing it per each TPM transaction, it does it once for the duration of
a TPM command.

Not sure if that will make things better or worse for you, but it would be
good to try in case it makes a difference.

[0]: http://git.infradead.org/users/jjs/linux-tpmdd.git/commit/667dcc75be864ff4c17cf58891853b7393bba3e2
[1]: http://git.infradead.org/users/jjs/linux-tpmdd.git/commit/db3248e8a036c39141c8f7e9f1cf5c5ae6815f76

> Many thanks,
> James.
>

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