linux-kernel - Re: [PATCH v5 16/17] tpm: take TPM chip power gating out of tpm

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Message-ID: <20181113155238.GB4601@linux.intel.com>
Date:   Tue, 13 Nov 2018 17:52:38 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     "Winkler, Tomas" <tomas.winkler@...el.com>
Cc:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        "Struk, Tadeusz" <tadeusz.struk@...el.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 16/17] tpm: take TPM chip power gating out of
 tpm_transmit()

On Tue, Nov 13, 2018 at 11:58:58AM +0000, Winkler, Tomas wrote:
> Yes, w/o this constrain it would be okay to request locality only once, 
> we can ask tboot ask again but at the time the requirement was that locality can be taken of at any point, 
> I believe that the locality won't be granted till a single command is completed.

But then tboot could race between requesting a locality and sending
the command (like immediately after the locality has been granted).

> Anyhow still the power gating is wrong in this patch do not ignore
> that part.

I can certainly take steps back with gating. It is not a blocker for
other changes but I do need to explain it in the changelog what problem
does cause. I'm not ignoring it. I just don't understad what is wrong.

> Thanks
> Tomas

/Jarkko