Re: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount()

From	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount()
Date	2017-09-13 03:10 +0200
Message-ID	<up4lI-wf-5@gated-at.bofh.it> (permalink)
References	<umI5X-1TZ-3@gated-at.bofh.it> <umI5X-1TZ-17@gated-at.bofh.it>
Organization	Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

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On Wed, Sep 06, 2017 at 08:56:38AM -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 5 msec 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@linux.vnet.ibm.com>
> Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> ---
>  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 d1eab29cb447..d710bbc4608b 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -169,7 +169,7 @@ static int get_burstcount(struct tpm_chip *chip)
>  		burstcnt = (value >> 8) & 0xFFFF;
>  		if (burstcnt)
>  			return burstcnt;
> -		tpm_msleep(TPM_TIMEOUT);
> +		tpm_msleep(1);
>  	} while (time_before(jiffies, stop));
>  	return -EBUSY;
>  }
> -- 
> 2.13.3

How did you pick 1 ms delay? Should there be a constant defining it?

/Jarkko

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Re: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount() Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-09-13 03:10 +0200
  Re: [PATCH v2 3/4] tpm: reduce tpm_msleep() time in get_burstcount() Nayna Jain <nayna@linux.vnet.ibm.com> - 2017-09-15 14:50 +0200

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