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Commit 59f5a6b0 authored by Nayna Jain's avatar Nayna Jain Committed by Jarkko Sakkinen
Browse files

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: default avatarNayna Jain <nayna@linux.vnet.ibm.com>
Acked-by: default avatarJay Freyensee <why2jjj.linux@gmail.com>
Reviewed-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
parent 33bafe90

drivers/char/tpm/tpm-interface.c

+1 −1
Original line number Diff line number Diff line
@@ -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));

drivers/char/tpm/tpm.h

+2 −1
Original line number Diff line number Diff line
@@ -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 */

drivers/char/tpm/tpm_tis_core.c

+2 −8
Original line number Diff line number Diff line
@@ -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 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask, 
		}

	} 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;

}