Re: [PATCH v2] tpm: Call cmd_ready/go_idle for each command transmission

[Mario Limonciello]

On 9/1/26 12:37, Jarkko Sakkinen wrote:

On Tue, Sep 01, 2026 at 11:32:15AM -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.

The current implementation calls cmd_ready once during tpm_chip_start()
and go_idle once during tpm_chip_stop(). For fTPM, when multiple commands
are sent without per-command idle transitions, subsequent commands timeout
as the TPM is waiting for the transition.

Fix this by calling cmd_ready before each command and go_idle on all exit
paths in tpm_try_transmit(). For TPM implementations that don't require
per-command transitions, the callbacks return immediately based on the
start method.

Remove the now-redundant per-session calls from tpm_chip_start() and
tpm_chip_stop() along with their helpers.

This resolves timeout errors during TPM initialization on systems where
BIOS has already performed TPM startup.

Signed-off-by: Mario Limonciello <mario.limoncie...@amd.com>
---
v2:
  * Drop redundant calls
  * Update commit message
---
  drivers/char/tpm/tpm-chip.c      | 24 ------------------------
  drivers/char/tpm/tpm-interface.c | 26 ++++++++++++++++++++++----
  2 files changed, 22 insertions(+), 28 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 12b7394b34bdc..0be5dbfaa72eb 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -66,22 +66,6 @@ static void tpm_relinquish_locality(struct tpm_chip *chip)
        chip->locality = -1;
  }

-static int tpm_cmd_ready(struct tpm_chip *chip)

-{
-       if (!chip->ops->cmd_ready)
-               return 0;
-
-       return chip->ops->cmd_ready(chip);
-}
-
-static int tpm_go_idle(struct tpm_chip *chip)
-{
-       if (!chip->ops->go_idle)
-               return 0;
-
-       return chip->ops->go_idle(chip);
-}
-
  static void tpm_clk_enable(struct tpm_chip *chip)
  {
        if (chip->ops->clk_enable)
@@ -116,13 +100,6 @@ int tpm_chip_start(struct tpm_chip *chip)
                }
        }

- ret = tpm_cmd_ready(chip);

-       if (ret) {
-               tpm_relinquish_locality(chip);
-               tpm_clk_disable(chip);
-               return ret;
-       }
-
        return 0;
  }
  EXPORT_SYMBOL_GPL(tpm_chip_start);
@@ -137,7 +114,6 @@ EXPORT_SYMBOL_GPL(tpm_chip_start);
   */
  void tpm_chip_stop(struct tpm_chip *chip)
  {
-       tpm_go_idle(chip);
        tpm_relinquish_locality(chip);
        tpm_clk_disable(chip);
  }
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index f745a098908b3..c5b5b5ba41821 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -113,12 +113,21 @@ 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;
+               }
+       }

I'd consider retaining tpm_go_idle and do this after arming the command:

        chip = chip __free(tpm_go_idle);

Good idea; that would be a lot less cleanup changes.  I'll modify and test.

+
        rc = chip->ops->send(chip, buf, bufsiz, count);
        if (rc < 0) {
                if (rc != -EPIPE)
                        dev_err(&chip->dev,
                                "%s: send(): error %d\n", __func__, rc);
-               return rc;
+               goto out;
        }

/*

@@ -152,7 +161,8 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void 
*buf, size_t bufsiz)

if (tpm_chip_req_canceled(chip, status)) {

                        dev_err(&chip->dev, "Operation Canceled\n");
-                       return -ECANCELED;
+                       rc = -ECANCELED;
+                       goto out;
                }

tpm_msleep(TPM_TIMEOUT_POLL);

@@ -168,19 +178,27 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, 
void *buf, size_t bufsiz)

tpm_chip_cancel(chip);

        dev_err(&chip->dev, "Operation Timed out\n");
-       return -ETIME;
+       rc = -ETIME;
+       goto out;

out_recv:

        len = chip->ops->recv(chip, buf, bufsiz);
        if (len < 0) {
                rc = len;
                dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
-               return rc;
+               goto out;
        }
  out_sync:
        if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
                rc = -EFAULT;

+out:

+       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

BR, Jarkko