On Fri, Mar 07, 2025 at 12:23:11AM +0200, Jarkko Sakkinen wrote:
> On Thu, Mar 06, 2025 at 09:00:56AM +0000, Jonathan McDowell wrote:
> > From: Jonathan McDowell <nood...@meta.com>
> >
> > Some Infineon devices have a issue where the status register will get
> > stuck with a quick REQUEST_USE / COMMAND_READY sequence. This is not
> > simply a matter of requiring a longer timeout; the work around is to
> > retry the command submission. Add appropriate logic to do this in the
> > send path.
> >
> > This is fixed in later firmware revisions, but those are not always
> > available, and cannot generally be easily updated from outside a
> > firmware environment.
> >
> > Testing has been performed with a simple repeated loop of doing a
> > TPM2_CC_GET_CAPABILITY for TPM_CAP_PROP_MANUFACTURER using the Go code
> > at:
> >
> > https://the.earth.li/~noodles/tpm-stuff/timeout-reproducer-simple.go
> >
> > It can take several hours to reproduce, and millions of operations.
> >
> > Signed-off-by: Jonathan McDowell <nood...@meta.com>
> > ---
> > drivers/char/tpm/tpm_tis_core.c | 17 ++++++++++++++---
> > drivers/char/tpm/tpm_tis_core.h | 1 +
> > include/linux/tpm.h | 1 +
> > 3 files changed, 16 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm_tis_core.c
> > b/drivers/char/tpm/tpm_tis_core.c
> > index 167d71747666..e4eae206a353 100644
> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -464,7 +464,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip,
> > const u8 *buf, size_t len)
> >
> > if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> > &priv->int_queue, false) < 0) {
> > - rc = -ETIME;
> > + if (test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags))
> > + rc = -EAGAIN;
> > + else
> > + rc = -ETIME;
> > goto out_err;
> > }
> > status = tpm_tis_status(chip);
> > @@ -481,7 +484,10 @@ static int tpm_tis_send_data(struct tpm_chip *chip,
> > const u8 *buf, size_t len)
> >
> > if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
> > &priv->int_queue, false) < 0) {
> > - rc = -ETIME;
> > + if (test_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags))
> > + rc = -EAGAIN;
> > + else
> > + rc = -ETIME;
>
> I'd encapsulate this inside wait_for_tpm_stat().
I think that gets a bit more complicated; this is an errata in the send
command path, for a stuck VALID bit, and the fix is to restart the whole
command send (i.e. we need to kick the TPM with tpm_tis_ready() etc).
I'm not sure returning EAGAIN in wait_for_tpm_stat() then makes
tpm_tis_send_data() any simpler.
> > goto out_err;
> > }
> > status = tpm_tis_status(chip);
> > @@ -546,9 +552,11 @@ static int tpm_tis_send_main(struct tpm_chip *chip,
> > const u8 *buf, size_t len)
> > if (rc >= 0)
> > /* Data transfer done successfully */
> > break;
> > - else if (rc != -EIO)
> > + else if (rc != EAGAIN && rc != -EIO)
> > /* Data transfer failed, not recoverable */
> > return rc;
> > +
> > + usleep_range(priv->timeout_min, priv->timeout_max);
> > }
> >
> > /* go and do it */
> > @@ -1144,6 +1152,9 @@ int tpm_tis_core_init(struct device *dev, struct
> > tpm_tis_data *priv, int irq,
> > priv->timeout_max = TIS_TIMEOUT_MAX_ATML;
> > }
> >
> > + if (priv->manufacturer_id == TPM_VID_IFX)
> > + set_bit(TPM_TIS_STATUS_WORKAROUND, &priv->flags);
> > +
> > if (is_bsw()) {
> > priv->ilb_base_addr = ioremap(INTEL_LEGACY_BLK_BASE_ADDR,
> > ILB_REMAP_SIZE);
> > diff --git a/drivers/char/tpm/tpm_tis_core.h
> > b/drivers/char/tpm/tpm_tis_core.h
> > index 690ad8e9b731..ce97b58dc005 100644
> > --- a/drivers/char/tpm/tpm_tis_core.h
> > +++ b/drivers/char/tpm/tpm_tis_core.h
> > @@ -89,6 +89,7 @@ enum tpm_tis_flags {
> > TPM_TIS_INVALID_STATUS = 1,
> > TPM_TIS_DEFAULT_CANCELLATION = 2,
> > TPM_TIS_IRQ_TESTED = 3,
> > + TPM_TIS_STATUS_WORKAROUND = 4,
>
> TPM_TIS_TIMEOUT_AGAIN or maybe *_REPEAT? The current name does
> not tell anything.
Yeah, TPM_TIS_STATUS_VALID_RETRY is perhaps clearer; it's not a timeout,
and we're looking to do a retry based on STS_VALID.
> > };
> >
> > struct tpm_tis_data {
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index 20a40ade8030..6c3125300c00 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -335,6 +335,7 @@ enum tpm2_cc_attrs {
> > #define TPM_VID_WINBOND 0x1050
> > #define TPM_VID_STM 0x104A
> > #define TPM_VID_ATML 0x1114
> > +#define TPM_VID_IFX 0x15D1
> >
> > enum tpm_chip_flags {
> > TPM_CHIP_FLAG_BOOTSTRAPPED = BIT(0),
J.
--
... "What's the philosophical difference between a killfile and the
automoderation?" "A killfile throws away good posts. Automoderation
throws away bad posts." -- Jonathan H N Chin to Calle Dybedahl
