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From: Nayna Jain <nayna@linux.vnet.ibm.com>
To: linux-integrity@vger.kernel.org
Cc: zohar@linux.vnet.ibm.com, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, peterhuewe@gmx.de,
	jarkko.sakkinen@linux.intel.com, tpmdd@selhorst.net,
	jgunthorpe@obsidianresearch.com, patrickc@us.ibm.com,
	Nayna Jain <nayna@linux.vnet.ibm.com>
Subject: [PATCH v3 0/2] tpm: improving granularity in poll sleep times
Date: Mon,  7 May 2018 12:07:31 -0400	[thread overview]
Message-ID: <20180507160733.8817-1-nayna@linux.vnet.ibm.com> (raw)

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()
directly.

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
behavior.

Changelog:

v3:
 
tpm: reduce poll sleep time in tpm_transmit()
* added testing platform information
* updated patch description for more clarity on reasoning

tpm: reduce polling time to usecs for even finer granularity
* added testing platform information
* added Jarkko's and Mimi's Reviewed-by
 
v2:

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(-)

-- 
2.13.3

             reply	other threads:[~2018-05-07 16:07 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-07 16:07 Nayna Jain [this message]
2018-05-07 16:07 ` [PATCH v3 1/2] tpm: reduce poll sleep time in tpm_transmit() Nayna Jain
2018-05-08 16:34   ` J Freyensee
2018-05-10 12:41     ` Nayna Jain
2018-05-14 10:39       ` Nayna Jain
2018-05-14 10:46   ` Jarkko Sakkinen
2018-05-14 10:47     ` Jarkko Sakkinen
2018-05-07 16:07 ` [PATCH v3 2/2] tpm: reduce polling time to usecs for even finer granularity Nayna Jain
2018-05-08 16:34   ` J Freyensee
2018-05-14 10:52   ` Jarkko Sakkinen

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