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Date: Wed, 18 Oct 2017 18:24:47 +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 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> /Jarkko > --- > drivers/char/tpm/tpm_tis_core.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c > index 993328ae988c..8b55fdaa67f2 100644 > --- a/drivers/char/tpm/tpm_tis_core.c > +++ b/drivers/char/tpm/tpm_tis_core.c > @@ -31,6 +31,12 @@ > #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 bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask, > bool check_cancel, bool *canceled) > { > @@ -82,7 +88,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask, > } > } else { > do { > - tpm_msleep(TPM_TIMEOUT); > + tpm_msleep(TPM_POLL_SLEEP); > status = chip->ops->status(chip); > if ((status & mask) == mask) > return 0; > @@ -224,7 +230,7 @@ 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 >
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