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

Shaikh, Azhar
2017-12-18T19:34:31Z

>-----Original Message-----
>From: Javier Martinez Canillas [mailto:javierm@redhat.com]
>Sent: Monday, December 18, 2017 11:30 AM
>To: Jason Gunthorpe <jgg@ziepe.ca>
>Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>; James Ettle
><james@ettle.org.uk>; linux-integrity@vger.kernel.org; Shaikh, Azhar
><azhar.shaikh@intel.com>; linux-kernel@vger.kernel.org;
>james.l.morris@oracle.com
>Subject: Re: [BISECTED] tpm CLKRUN breaks PS/2 keyboard and touchpad on
>Braswell system
>
>Hello Jason,
>
>Thanks a lot for your feedback.
>
>On 12/18/2017 06:55 PM, Jason Gunthorpe wrote:
>> On Mon, Dec 18, 2017 at 01:29:01PM +0100, Javier Martinez Canillas wrote:
>>> On 12/18/2017 01:22 PM, Javier Martinez Canillas wrote:
>>>
>>> [snip]
>>>
>>>>
>>>> James,
>>>>
>>>> Can you please test the following (untested) patch on top of the
>>>> other two mentioned patches to see if it makes a difference for you?
>>>>
>>>
>>> I should had tried to at least compile the patch :)
>>
>> I think this is backwards..
>>
>> If CLKRUN_EN is on (eg power management is NOT enabled on LPC) then
>> TPM shouldn't do anything at all.
>>
>> If CLKRUN_EN is off, then it should try to turn it on/off to save
>> power.
>>
>
>My knowledge of LPC is near to non-existent so I please forgive me if I'm
>wrong, but my understanding is that it's the opposite of what you said.
>
>When CLKRUN_EN is SET, power management is ENABLED on the LPC bus and
>the host LCLK clock may be stopped when entering in some low-power states.
>
>The CLKRUN# signal is then used by peripherals to restart the LCLK clock after
>resuming from low-power states to be able to transmit again.
>
>When CLKRUN_EN is CLEAR, power management is DISABLED on the LPC bus
>and the host LCLK clock is never stopped even when entering in some low-
>power states.
>

Hi Javier,

Yes you are correct with the above understanding of the CLKRUN.

>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.

Since I do not have an end product to test this on, I managed to get one BSW Reference Verification Platform(RVP). I flashed the latest Ubuntu (17.10) which is on 4.13.13 kernel version and does have the patch.

I was able to use the PS/2 mouse and keyboard immediately after bootup and also after suspend/resume cycle. The system does have a TPM.(/dev/tpm0 and /dev/tpmrm0 exist)

>And that was the motivation of commit 5e572cab92f0 ("tpm: Enable CLKRUN
>protocol for Braswell systems") that introduced the regression.
>
>> Perhaps the best work around is to just delete the turning off of
>> CLKRUN_EN ? Uses more power but keeps the clock running which should
>> keep both TPM and superio happy.
>>
>
>But that's exactly the goal of the commit 5e572cab92f0, to disable the CLKRUN
>protocol (probably for what I mentioned before). So doing so will cause issues
>for those systems again.
>
>What the patch I shared with James does is to avoid disabling the CLKRUN_EN
>if this is already disabled. Which should be a no-op anyways but the problem
>is that latter it's enabled even when the driver found disabled to start with.
>
>I still don't like the overall solution since it's too error prone. Touching a global
>bus configuration in a driver for a single peripheral isn't safe to say the least.
>
>But regardless of that, the patch I shared has merits on its own since is wrong
>to keep the bus configuration in a different state that was before the driver
>was probed. And in fact, James reported that it makes his system to work
>again.
>
>> Jason
>>
>
>Best regards,
>--
>Javier Martinez Canillas
>Software Engineer - Desktop Hardware Enablement Red Hat