Message-ID: <548DA33A.4010300@linux.vnet.ibm.com>
Date: Sun, 14 Dec 2014 09:48:26 -0500
From: Stefan Berger <stefanb@linux.vnet.ibm.com>
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To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Peter Huewe <peterhuewe@gmx.de>, Ashley Lai <ashley@ashleylai.com>,
        Marcel Selhorst <tpmdd@selhorst.net>
CC: tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
        josh@joshtriplett.org, christophe.ricard@gmail.com,
        jason.gunthorpe@obsidianresearch.com, linux-api@vger.kernel.org,
        trousers-tech@lists.sourceforge.net,
        Will Arthur <will.c.arthur@intel.com>
Subject: Re: [PATCH v10 8/8] tpm: TPM 2.0 FIFO Interface
References: <1418413600-5400-1-git-send-email-jarkko.sakkinen@linux.intel.com> <1418413600-5400-9-git-send-email-jarkko.sakkinen@linux.intel.com>
In-Reply-To: <1418413600-5400-9-git-send-email-jarkko.sakkinen@linux.intel.com>
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Sender: linux-kernel-owner@vger.kernel.org

On 12/12/2014 02:46 PM, Jarkko Sakkinen wrote:
> Detect TPM 2.0 by sending idempotent TPM 2.x command. Ordinals for
> TPM 2.0 are higher than TPM 1.x commands so this should be fail-safe.
> Using STS3 is unreliable because some chips just report 0xff and not
> what the spec says.

TPM TIS 1.2 can report either 0xff or 0x00 for sts3 since that part of 
register was not defined for this version but only for a later version. 
So, unless the TIS 1.3 for TPM 2.0 is broken, it should report a bit 
_pattern_ (not plain 0x00 or 0xff) that you could apply the suggested 
mask to and check then.

     Stefan

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