Since kernel 4.14, we fixed the TPM sleep logic from msleep to usleep_range, so that the TPM sleeps exactly with TPM_TIMEOUT (=5ms) afterward. Before that fix, msleep(5) actually sleeps for around 15ms. The fix is https://github.com/torvalds/linux/commit/9f3fc7bcddcb51234e23494531f93ab60475e1c3 That fix uncovered that the TPM_TIMEOUT was not properly set previously. We recently found the TPM driver in kernel 4.14+ (including 5.9-rc4) crashes Atmel TPM chips with too frequent TPM queries. The TPM crash signature is ``` $ tpm_sealdata -z Tspi_Key_LoadKey failed: 0x00001087 - layer=tddl, code=0087 (135), I/O error $ sudo dmesg | grep tpm0 [59154.665549] tpm tpm0: tpm_try_transmit: send(): error -62 [59154.809532] tpm tpm0: tpm_try_transmit: send(): error -62 ``` >From the error code "-62", it looks similar to another bug https://patchwork.kernel.org/patch/10520247/ where the "TPM_TIMEOUT_USECS_MAX" and "TPM_TIMEOUT_USEC_MIN" is too small, which causes TPM get queried too frequently, and thus crashes. This patch fix the TPM_TIMEOUT to 15ms which was the actual timeout TPM chips use before the fix from msleep to usleep_range. Thus fixed the crash. Test Plan: - Run fixed kernel on system with Atmel TPM chips and ensure crash does not happen - Run fixed kernel on system with other TPM chips (IFX / WEC / STM) ensure not breakages from tpm-tool --- drivers/char/tpm/tpm.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index 947d1db0a5cc..73259ac0a997 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -37,7 +37,7 @@ #define TPM_RETRY 50 enum tpm_timeout { - TPM_TIMEOUT = 5, /* msecs */ + TPM_TIMEOUT = 15, /* msecs */ TPM_TIMEOUT_RETRY = 100, /* msecs */ TPM_TIMEOUT_RANGE_US = 300, /* usecs */ TPM_TIMEOUT_POLL = 1, /* msecs */ -- 2.17.1
