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| author | Nayna Jain <nayna@linux.vnet.ibm.com> | 2018-05-16 08:51:25 +0300 |
|---|---|---|
| committer | Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> | 2018-05-18 10:00:01 +0300 |
| commit | 424eaf910c329ab06ad03a527ef45dcf6a328f00 (patch) | |
| tree | f84106c4dbbd71c5c6f665486819cdf59cce5bb2 /drivers/char/tpm/tpm.h | |
| parent | f5495bb9aca4ccd46a14161bf2d9dd72c8b7166e (diff) | |
| download | linux-424eaf910c329ab06ad03a527ef45dcf6a328f00.tar.xz | |
tpm: reduce polling time to usecs for even finer granularity
The TPM burstcount and status commands are supposed to return very
quickly [2][3]. This patch further reduces the TPM poll sleep time to usecs
in get_burstcount() and wait_for_tpm_stat() by calling usleep_range()
directly.
After this change, performance on a system[1] with a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~10.7 sec to ~7 sec.
[1] All tests are performed on an x86 based, locked down, single purpose
closed system. It has Infineon TPM 1.2 using LPC Bus.
[2] From the TCG Specification "TCG PC Client Specific TPM Interface
Specification (TIS), Family 1.2":
"NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would
take 84 us, which is a long time to stall the CPU. Chipsets may not be
designed to post this much data to LPC; therefore, the CPU itself is
stalled for much of this time. Sending 1 kB would take 350 μs. Therefore,
even if the TPM_STS_x.burstCount field is a high value, software SHOULD
be interruptible during this period."
[3] From the TCG Specification 2.0, "TCG PC Client Platform TPM Profile
(PTP) Specification":
"It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take
84 us. Chipsets may not be designed to post this much data to LPC;
therefore, the CPU itself is stalled for much of this time. Sending 1 kB
would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a
high value, software should be interruptible during this period. For SPI,
assuming 20MHz clock and 64-byte transfers, it would take about 120 usec
to move 256B of data. Sending 1kB would take about 500 usec. If the
transactions are done using 4 bytes at a time, then it would take about
1 msec. to transfer 1kB of data."
Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Jay Freyensee <why2jjj.linux@gmail.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Diffstat (limited to 'drivers/char/tpm/tpm.h')
| -rw-r--r-- | drivers/char/tpm/tpm.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index baa066997372..4426649e431c 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -54,7 +54,9 @@ enum tpm_timeout { TPM_TIMEOUT = 5, /* msecs */ TPM_TIMEOUT_RETRY = 100, /* msecs */ TPM_TIMEOUT_RANGE_US = 300, /* usecs */ - TPM_TIMEOUT_POLL = 1 /* msecs */ + TPM_TIMEOUT_POLL = 1, /* msecs */ + TPM_TIMEOUT_USECS_MIN = 100, /* usecs */ + TPM_TIMEOUT_USECS_MAX = 500 /* usecs */ }; /* TPM addresses */ |