On Mon, Aug 31, 2026 at 12:37:21AM -0500, Mario Limonciello wrote: > Some TPM implementations, particularly fTPM using the CRB interface, > require the TPM to transition through idle and ready states for each > command rather than once per session. > > According to the TCG PC Client Platform TPM Profile (PTP) specification, > the CRB interface includes an idle/ready handshake for power management. > Software should set cmdReady to transition the TPM from idle to ready > state before sending a command, and set goIdle when finished to allow > the TPM to enter a low-power state. > > The current implementation calls cmd_ready once during tpm_chip_start() > and go_idle once during tpm_chip_stop(). During the startup sequence, > multiple commands are sent between these calls (self-test, get > capabilities, session init). For fTPM, when subsequent commands are sent > without transitioning to idle after the previous command completes, those > commands timeout as the TPM is waiting for the idle transition. > > Fix this by calling cmd_ready before each command transmission and > go_idle after receiving each response in tpm_try_transmit(). For TPM > implementations that don't require per-command transitions, the callbacks > can return immediately (as many already do based on the start method). > > This resolves timeout errors during TPM initialization on systems where > BIOS has already performed TPM startup, as the kernel can now properly > communicate with the fTPM during auto-startup. > > Signed-off-by: Mario Limonciello <[email protected]> > --- > drivers/char/tpm/tpm-interface.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/char/tpm/tpm-interface.c > b/drivers/char/tpm/tpm-interface.c > index f745a098908b3..a98ddca876152 100644 > --- a/drivers/char/tpm/tpm-interface.c > +++ b/drivers/char/tpm/tpm-interface.c > @@ -113,6 +113,15 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, > void *buf, size_t bufsiz) > return -E2BIG; > } > > + if (chip->ops->cmd_ready) { > + rc = chip->ops->cmd_ready(chip); > + if (rc) { > + dev_err(&chip->dev, > + "%s: cmd_ready(): error %d\n", __func__, rc); > + return rc; > + } > + } > + > rc = chip->ops->send(chip, buf, bufsiz, count); > if (rc < 0) { > if (rc != -EPIPE) > @@ -181,6 +190,12 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, > void *buf, size_t bufsiz) > if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length)) > rc = -EFAULT; > > + if (chip->ops->go_idle) { > + int idle_rc = chip->ops->go_idle(chip); > + if (idle_rc && !rc) > + rc = idle_rc; > + } > + > return rc ? rc : len; > } > > -- > 2.43.0 >
I think this should remove also redundant calls to cmd_ready and go_idle. BR, Jarkko
