linux-kernel - Re: [PATCH v4 3/4] tpm: reduce tpm polling delay in tpm_tis

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Date:   Thu, 19 Oct 2017 17:22:44 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Nayna Jain <nayna@...ux.vnet.ibm.com>
Cc:     linux-integrity@...r.kernel.org, zohar@...ux.vnet.ibm.com,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterhuewe@....de,
        tpmdd@...horst.net, jgunthorpe@...idianresearch.com,
        patrickc@...ibm.com
Subject: Re: [PATCH v4 3/4] tpm: reduce tpm polling delay in tpm_tis_core

On Wed, Oct 18, 2017 at 06:24:47PM +0300, Jarkko Sakkinen wrote:
> On Tue, Oct 17, 2017 at 04:32:31PM -0400, Nayna Jain wrote:
> > The existing wait_for_tpm_stat() polls for the chip status after
> > 5msec sleep. As per TCG ddwg input, it is expected that tpm might
> > return status in few usec. So, reducing the delay in polling to
> > 1msec.
> > Similarly, get_burstcount() function sleeps for 5msec before
> > retrying for next query to burstcount in a loop. If it takes
> > lesser time for TPM to return, this 5msec delay is longer than
> > necessary.
> > 
> > After this change, performance on a TPM 1.2 with an 8 byte
> > burstcount for 1000 extends improved from ~14sec to ~9sec.
> > 
> > Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
> 
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

Tested-by: Jarkko Sakkinen <jarkkko.sakkinen@...ux.intel.com>

/Jarkko