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SubjectRe: [PATCH v3 3/5] tpm: reduce polling delay in tpm_tis wait_for_tpm_stat()
On Wed, Oct 04, 2017 at 06:29:22AM -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.
>
> After this change, performance on a TPM 1.2 with an 8 byte
> burstcount for 1000 extends improved from ~14sec to ~10sec.
>
> Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
> ---
> drivers/char/tpm/tpm_tis_core.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 8da425e1783f..224842e06105 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -31,6 +31,8 @@
> #include "tpm.h"
> #include "tpm_tis_core.h"
>
> +#define TPM_POLL_SLEEP 1

Should have a comment above that explains the choice.

> +
> static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
> bool check_cancel, bool *canceled)
> {
> @@ -82,7 +84,7 @@ 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;
> --
> 2.13.3
>

/Jarkko

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