linux-kernel - Re: [PATCH] tpm_tis: turn on TPM before calling tpm_get

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Date:   Thu, 14 Nov 2019 18:49:49 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Jerry Snitselaar <jsnitsel@...hat.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Peter Huewe <peterhuewe@....de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-stable@...r.kernel.org,
        Christian Bundy <christianbundy@...ction.io>
Subject: Re: [PATCH] tpm_tis: turn on TPM before calling tpm_get_timeouts

On Tue, Nov 12, 2019 at 04:26:23PM -0400, Jason Gunthorpe wrote:
> On Tue, Nov 12, 2019 at 01:23:33PM -0700, Jerry Snitselaar wrote:
> > On Tue, Nov 12, 2019 at 1:03 PM Jarkko Sakkinen
> > <jarkko.sakkinen@...ux.intel.com> wrote:
> > >
> > > On Mon, Nov 11, 2019 at 04:34:18PM -0700, Jerry Snitselaar wrote:
> > > > With power gating moved out of the tpm_transmit code we need
> > > > to power on the TPM prior to calling tpm_get_timeouts.
> > > >
> > > > Cc: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > > > Cc: Peter Huewe <peterhuewe@....de>
> > > > Cc: Jason Gunthorpe <jgg@...pe.ca>
> > > > Cc: linux-kernel@...r.kernel.org
> > > > Cc: linux-stable@...r.kernel.org
> > > > Fixes: a3fbfae82b4c ("tpm: take TPM chip power gating out of tpm_transmit()")
> > > > Reported-by: Christian Bundy <christianbundy@...ction.io>
> > > > Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
> > > >  drivers/char/tpm/tpm_tis_core.c | 3 ++-
> > > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > > > index 270f43acbb77..cb101cec8f8b 100644
> > > > +++ b/drivers/char/tpm/tpm_tis_core.c
> > > > @@ -974,13 +974,14 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
> > > >                * to make sure it works. May as well use that command to set the
> > > >                * proper timeouts for the driver.
> > > >                */
> > > > +             tpm_chip_start(chip);
> > > >               if (tpm_get_timeouts(chip)) {
> > > >                       dev_err(dev, "Could not get TPM timeouts and durations\n");
> > > >                       rc = -ENODEV;
> > > > +                     tpm_stop_chip(chip);
> > > >                       goto out_err;
> > > >               }
> > >
> > > Couldn't this call just be removed?
> > >
> > > /Jarkko
> > >
> > 
> > Probably. It will eventually get called when tpm_chip_register
> > happens. I don't know what the reason was for trying it prior to the
> > irq probe.
> 
> At least tis once needed the timeouts before registration because it
> was issuing TPM commands to complete its setup.
> 
> If timeouts have not been set then no TPM command should be executed.

Not true since you need a TPM command to set them. That is why they
have been set initially to maximum possible values.

/Jarkko