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

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Date:   Wed, 20 Dec 2017 15:41:55 +0000
From:   "Shaikh, Azhar" <azhar.shaikh@...el.com>
To:     Javier Martinez Canillas <javierm@...hat.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>
CC:     "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>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "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



>-----Original Message-----
>From: Javier Martinez Canillas [mailto:javierm@...hat.com]
>Sent: Wednesday, December 20, 2017 7:31 AM
>To: Shaikh, Azhar <azhar.shaikh@...el.com>;
>Alexander.Steffen@...ineon.com; hdegoede@...hat.com; linux-
>kernel@...r.kernel.org
>Cc: james@...le.org.uk; arnd@...db.de; jarkko.sakkinen@...ux.intel.com;
>peterhuewe@....de; jgg@...pe.ca; gregkh@...uxfoundation.org; linux-
>integrity@...r.kernel.org
>Subject: Re: [PATCH 0/4] tpm: fix PS/2 devices not working on Braswell
>systems due CLKRUN enabled
>
>Hello Azhar,
>
>On 12/20/2017 04:08 PM, Shaikh, Azhar wrote:
>
>[snip]
>
>>>>
>>>>> It seems that on machines with a PS/2 controller connected to the
>>>>> LPC bus the BIOS is already doing this, so I've a feeling that it
>>>>> not being done on devices with a TPM is a bug in the firmware
>>>>
>>>> Absolutely agree, system integratos should make sure that all the
>>>> devices connected to the LPC either have CLKRUN protocol support and
>>>> is enabled or disable the CLKRUN protocol permanently.
>>>
>>> As far as I understand it, this is exactly the issue here: They know
>>> that there are devices that do not support the CLKRUN protocol (the
>>> TPM in this case), but they still need to enable it to prevent other
>>> issues. So for the TPM to continue to work, CLKRUN needs to be
>>> disabled temporarily while the TPM is active.
>>>
>>
>> Yes that was the reason to have this fix. We needed CLKRUN to be enabled
>for Braswell SOC . But the TPM in this case SLB9655 does not support CLKRUN
>(please check this public documentation
>https://www.infineon.com/dgdl/Infineon-TPM+SLB+9665-DS-v10_15-
>EN.pdf?fileId=5546d4625185e0e201518b83d9273d87 section 2.3 Power
>Management). So as Alexander mentioned CLKRUN is disabled while TPM
>transactions are in progress.
>>
>
>Yes I do understand that. Please read my answer to Alexander's email and
>also my question (and Hans') about keeping the CLKRUN protocol
>permanently disabled.
>

We had to enable CLKRUN for BSW issues as mentioned here https://www.intel.com/content/www/us/en/processors/pentium/pentium-celeron-n-series-spec-update.html  on Page 24 CHP 49 and Page 25 CHP 51



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