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tpm: reduce poll sleep time in tpm_transmit() 

tpm_try_transmit currently checks TPM status every 5 msecs between
send and recv. It does so in a loop for the maximum timeout as defined
in the TPM Interface Specification. However, the TPM may return before
5 msecs. Thus the polling interval for each iteration can be reduced,
which improves overall performance. This patch changes the polling sleep
time from 5 msecs to 1 msec.

Additionally, this patch renames TPM_POLL_SLEEP to TPM_TIMEOUT_POLL and
moves it to tpm.h as an enum value.

After this change, performance on a system[1] with a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~14 sec to ~10.7 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.

Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
Acked-by: Jay Freyensee <why2jjj.linux@gmail.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
This commit is contained in:
Nayna Jain 2018-05-07 12:07:32 -04:00 committed by Jarkko Sakkinen
parent 33bafe9082
commit 59f5a6b07f
3 changed files with 5 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/char/tpm/tpm-interface.c
View File

@ -489,7 +489,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
goto out;
}
tpm_msleep(TPM_TIMEOUT);
tpm_msleep(TPM_TIMEOUT_POLL);
rmb();
} while (time_before(jiffies, stop));

3
drivers/char/tpm/tpm.h
View File

@ -53,7 +53,8 @@ enum tpm_const {
enum tpm_timeout {
TPM_TIMEOUT = 5, /* msecs */
TPM_TIMEOUT_RETRY = 100, /* msecs */
TPM_TIMEOUT_RANGE_US = 300 /* usecs */
TPM_TIMEOUT_RANGE_US = 300, /* usecs */
TPM_TIMEOUT_POLL = 1 /* msecs */
};
/* TPM addresses */

10
drivers/char/tpm/tpm_tis_core.c
View File

@ -31,12 +31,6 @@
#include "tpm.h"
#include "tpm_tis_core.h"
/* This is a polling delay to check for status and burstcount.
* As per ddwg input, expectation is that status check and burstcount
* check should return within few usecs.
*/
#define TPM_POLL_SLEEP 1 /* msec */
static void tpm_tis_clkrun_enable(struct tpm_chip *chip, bool value);
static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
@ -90,7 +84,7 @@ again:
}
} else {
do {
tpm_msleep(TPM_POLL_SLEEP);
tpm_msleep(TPM_TIMEOUT_POLL);
status = chip->ops->status(chip);
if ((status & mask) == mask)
return 0;
@ -279,7 +273,7 @@ static int get_burstcount(struct tpm_chip *chip)
burstcnt = (value >> 8) & 0xFFFF;
if (burstcnt)
return burstcnt;
tpm_msleep(TPM_POLL_SLEEP);
tpm_msleep(TPM_TIMEOUT_POLL);
} while (time_before(jiffies, stop));
return -EBUSY;
}