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Re: [PATCH v3 4/5] tpm: reduce tpm_msleep() time in get_burstcount()






On 10/12/2017 04:48 PM, Jarkko Sakkinen wrote:
On Wed, Oct 04, 2017 at 06:29:23AM -0400, Nayna Jain wrote:
Currently, get_burstcount() function sleeps for 5msec in a loop
before retrying for next query to burstcount. However, if it takes
lesser time for TPM to return, this 5msec delay is longer
than necessary.

This patch replaces the tpm_msleep time from 5msec to 1msec.

After this change, performance on a TPM 1.2 with an 8 byte
burstcount for 1000 extends improved from ~10sec to ~9sec.

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
Acked-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
---
  drivers/char/tpm/tpm_tis_core.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 224842e06105..826a0b9c9201 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -226,7 +226,7 @@ static int get_burstcount(struct tpm_chip *chip)
  		burstcnt = (value >> 8) & 0xFFFF;
  		if (burstcnt)
  			return burstcnt;
-		tpm_msleep(TPM_TIMEOUT);
+		tpm_msleep(TPM_POLL_SLEEP);
  	} while (time_before(jiffies, stop));
  	return -EBUSY;
  }
--
2.13.3

Would it make sense to squash this to 3/5 and merge the commit
messages?
Yeah.. it sounds reasonable.. both are reducing the sleep delay time for same purpose, just in different functions.

Thanks & Regards,
    - Nayna


/Jarkko