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

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Date:   Tue, 12 Nov 2019 16:26:23 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Jerry Snitselaar <jsnitsel@...hat.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.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 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.

Jason