Re: [PATCH] tpm: tpm_tis: Add optional delay after relinquish

Thank you Jarkko. I'll do that.

Jim

On Thu, May 21, 2026 at 4:48 PM Jarkko Sakkinen <[email protected]> wrote:
>
> On Mon, May 18, 2026 at 11:09:26PM -0700, Jim Broadus wrote:
> > Some TPMs fail to grant locality when requested immediately after being
> > relinquished. In this case, the TPM_ACCESS_REQUEST_USE bit of the
> > TPM_ACCESS register is cleared immediately without setting
> > TPM_ACCESS_ACTIVE_LOCALITY.
> >
> > This issue can be seen at boot since tpm_chip_start, called right
> > after locality is relinquished, fails. This causes the probe to fail:
> >
> > tpm_tis MSFT0101:00: probe with driver tpm_tis failed with error -1
> >
> > This occurs on some older Dell Latitudes and maybe others. To work
> > around this, add a "settle" boolean param to tpm_tis. When this is
> > enabled, a delay is added after locality is relinquished.
> >
> > Signed-off-by: Jim Broadus <[email protected]>
>
> It would be better idea first to replace priv->manufacturer_id with
> priv->did_vid, and make necessary changes to sites where it is used.
>
> Then in the if-statement compare DID/VID of the device to priv->did_vid
> and apply quirk only if it matches.
>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
> >  drivers/char/tpm/tpm_tis.c                      | 7 +++++++
> >  drivers/char/tpm/tpm_tis_core.c                 | 3 +++
> >  drivers/char/tpm/tpm_tis_core.h                 | 1 +
> >  4 files changed, 18 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 4d0f545fb3ec..5b7111033fbb 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -7651,6 +7651,13 @@ Kernel parameters
> >                       defined by Trusted Computing Group (TCG) see
> >                       https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
> >
> > +     tpm_tis.settle= [HW,TPM]
> > +                     Format: <bool>
> > +                     When enabled, this adds a delay after locality is
> > +                     relinquished. Some TPMs will fail to grant locality if
> > +                     requested immediately after being relinquished. This
> > +                     causes the probe to fail.
> > +
> >       tp_printk       [FTRACE]
> >                       Have the tracepoints sent to printk as well as the
> >                       tracing ring buffer. This is useful for early boot up
> > diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
> > index 9aa230a63616..8ac0ea78570e 100644
> > --- a/drivers/char/tpm/tpm_tis.c
> > +++ b/drivers/char/tpm/tpm_tis.c
> > @@ -101,6 +101,10 @@ module_param(force, bool, 0444);
> >  MODULE_PARM_DESC(force, "Force device probe rather than using ACPI entry");
> >  #endif
> >
> > +static bool settle;
> > +module_param(settle, bool, 0444);
> > +MODULE_PARM_DESC(settle, "Add settle time after relinquish");
> > +
> >  #if defined(CONFIG_PNP) && defined(CONFIG_ACPI)
> >  static int has_hid(struct acpi_device *dev, const char *hid)
> >  {
> > @@ -242,6 +246,9 @@ static int tpm_tis_init(struct device *dev, struct tpm_info *tpm_info)
> >       if (itpm || is_itpm(ACPI_COMPANION(dev)))
> >               set_bit(TPM_TIS_ITPM_WORKAROUND, &phy->priv.flags);
> >
> > +     if (settle)
> > +             set_bit(TPM_TIS_SETTLE_AFTER_RELINQUISH, &phy->priv.flags);
> > +
> >       return tpm_tis_core_init(dev, &phy->priv, irq, &tpm_tcg,
> >                                ACPI_HANDLE(dev));
> >  }
> > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > index 21d79ad3b164..68be26fa5817 100644
> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -184,6 +184,9 @@ static int tpm_tis_relinquish_locality(struct tpm_chip *chip, int l)
> >               __tpm_tis_relinquish_locality(priv, l);
> >       mutex_unlock(&priv->locality_count_mutex);
> >
> > +     if (test_bit(TPM_TIS_SETTLE_AFTER_RELINQUISH, &priv->flags))
> > +             tpm_msleep(TPM_TIMEOUT);
> > +
> >       return 0;
> >  }
> >
> > diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> > index 6c3aa480396b..413cac5e0f31 100644
> > --- a/drivers/char/tpm/tpm_tis_core.h
> > +++ b/drivers/char/tpm/tpm_tis_core.h
> > @@ -90,6 +90,7 @@ enum tpm_tis_flags {
> >       TPM_TIS_DEFAULT_CANCELLATION    = 2,
> >       TPM_TIS_IRQ_TESTED              = 3,
> >       TPM_TIS_STATUS_VALID_RETRY      = 4,
> > +     TPM_TIS_SETTLE_AFTER_RELINQUISH = 5,
> >  };
> >
> >  struct tpm_tis_data {
> > --
> > 2.54.0
> >
>
> BR, Jarkko