linux-kernel - Re: [PATCH 1/5] tpm: add functions to set and unset the tpm chips reset state

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Message-ID: <20220407142526.GW64706@ziepe.ca>
Date:   Thu, 7 Apr 2022 11:25:26 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     peterhuewe@....de, jarkko@...nel.org, =robh+dt@...nel.org,
        devicetree@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefanb@...ux.ibm.com,
        p.rosenberger@...bus.com, lukas@...ner.de
Subject: Re: [PATCH 1/5] tpm: add functions to set and unset the tpm chips
 reset state

On Thu, Apr 07, 2022 at 01:18:45PM +0200, Lino Sanfilippo wrote:
> Currently it is not possible to set the tpm chips reset state from within
> the driver. This is problematic if the chip is still in reset after the
> system comes up. This may e.g. happen if the reset line is pulled into
> reset state by a pin configuration in the device tree.

This kind of system is badly misdesigned.

TPM PCRs fundementally cannot work if the TPM reset line is under
software control.

Jason