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    SubjectRe: [PATCH v2 1/2] tpm: reduce poll sleep time in tpm_transmit()
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    On Tue, 2018-04-17 at 09:12 -0400, Nayna Jain wrote:
    > The TPM polling code in tpm_transmit sleeps in each loop iteration for
    > 5 msecs. However, the TPM might return earlier, and thus waiting for
    > 5 msecs adds an unnecessary delay. This patch reduces the polling sleep
    > time in tpm_transmit() from 5 msecs to 1 msecs.
    >
    > Additionally, this patch renames TPM_POLL_SLEEP and moves it to tpm.h as
    > an enum value.
    >
    > After this change, performance on a TPM 1.2 with an 8 byte burstcount
    > for 1000 extends improved from ~14 sec to ~10.7 sec.
    >
    > Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>

    Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

    > ---
    > drivers/char/tpm/tpm-interface.c | 2 +-
    > drivers/char/tpm/tpm.h | 3 ++-
    > drivers/char/tpm/tpm_tis_core.c | 10 ++--------
    > 3 files changed, 5 insertions(+), 10 deletions(-)
    >
    > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
    > index 9e80a953d693..a676d8ad5992 100644
    > --- a/drivers/char/tpm/tpm-interface.c
    > +++ b/drivers/char/tpm/tpm-interface.c
    > @@ -470,7 +470,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
    > goto out;
    > }
    >
    > - tpm_msleep(TPM_TIMEOUT);
    > + tpm_msleep(TPM_TIMEOUT_POLL);
    > rmb();
    > } while (time_before(jiffies, stop));
    >
    > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
    > index f895fba4e20d..7e797377e1eb 100644
    > --- a/drivers/char/tpm/tpm.h
    > +++ b/drivers/char/tpm/tpm.h
    > @@ -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 */
    > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
    > index da074e3db19b..021e6b68f2db 100644
    > --- a/drivers/char/tpm/tpm_tis_core.c
    > +++ b/drivers/char/tpm/tpm_tis_core.c
    > @@ -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;
    > @@ -232,7 +226,7 @@ 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;
    > }

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