[PATCH v2 0/2] tpm: improving granularity in poll sleep times

Nayna Jain nayna at linux.vnet.ibm.com
Tue Apr 17 13:12:44 UTC 2018

The existing TPM polling code sleeps in each loop iteration for time in
msecs ranging from 1 msecs to 5 msecs. However, many of the TPM commands
complete much faster, resulting in unnecessary delays.

This set of patches identifies such iterations and optimizes the sleep
time. The first patch replaces TPM_POLL_SLEEP with TPM_TIMEOUT_POLL and
moves it from tpm_tis_core.c to tpm.h as an enum with value 1 msecs. The
second patch further reduces the TPM poll sleep time in get_burstcount()
and wait_for_tpm_stat() in tpm_tis_core.c by calling usleep_range()

The change is only in the polling time, and the maximum timeout is still
maintained the same. Thus, it should not affect the overall existing


tpm: reduce poll sleep time in tpm_transmit()
* merged previously defined two patches into this. 
* updated patch description as per Jarkko's feedback

tpm: reduce polling time to usecs for even finer granularity
* directly use usleep_range with finer granularity less than 1msec

Nayna Jain (2):
  tpm: reduce poll sleep time in tpm_transmit()
  tpm: reduce polling time to usecs for even finer granularity

 drivers/char/tpm/tpm-interface.c |  2 +-
 drivers/char/tpm/tpm.h           |  5 ++++-
 drivers/char/tpm/tpm_tis_core.c  | 11 +++--------
 3 files changed, 8 insertions(+), 10 deletions(-)


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