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SubjectRe: [PATCH v4 2/4] tpm: ignore burstcount to improve tpm_tis send() performance
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On 10/20/2017 08:12 PM, Alexander.Steffen@infineon.com wrote:
>> The TPM burstcount status indicates the number of bytes that can
>> be sent to the TPM without causing bus wait states. Effectively,
>> it is the number of empty bytes in the command FIFO.
>>
>> This patch optimizes the tpm_tis_send_data() function by checking
>> the burstcount only once. And if the burstcount is valid, it writes
>> all the bytes at once, permitting wait state.
>>
>> After this change, performance on a TPM 1.2 with an 8 byte
>> burstcount for 1000 extends improved from ~41sec to ~14sec.
>>
>> Suggested-by: Ken Goldman<kgold@linux.vnet.ibm.com> in
>> conjunction with the TPM Device Driver work group.
>> 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 | 42 +++++++++++++++----------------------
>> ----
>> 1 file changed, 15 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm_tis_core.c
>> b/drivers/char/tpm/tpm_tis_core.c
>> index b33126a35694..993328ae988c 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -316,7 +316,6 @@ static int tpm_tis_send_data(struct tpm_chip *chip,
>> u8 *buf, size_t len)
>> {
>> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>> int rc, status, burstcnt;
>> - size_t count = 0;
>> bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND;
>>
>> status = tpm_tis_status(chip);
>> @@ -330,35 +329,24 @@ static int tpm_tis_send_data(struct tpm_chip *chip,
>> u8 *buf, size_t len)
>> }
>> }
>>
>> - while (count < len - 1) {
>> - burstcnt = get_burstcount(chip);
>> - if (burstcnt < 0) {
>> - dev_err(&chip->dev, "Unable to read burstcount\n");
>> - rc = burstcnt;
>> - goto out_err;
>> - }
>> - burstcnt = min_t(int, burstcnt, len - count - 1);
>> - rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv-
>>> locality),
>> - burstcnt, buf + count);
>> - if (rc < 0)
>> - goto out_err;
>> -
>> - count += burstcnt;
>> -
>> - if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip-
>>> timeout_c,
>> - &priv->int_queue, false) < 0) {
>> - rc = -ETIME;
>> - goto out_err;
>> - }
>> - status = tpm_tis_status(chip);
>> - if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) {
>> - rc = -EIO;
>> - goto out_err;
>> - }
>> + /*
>> + * Get the initial burstcount to ensure TPM is ready to
>> + * accept data.
>> + */
>> + burstcnt = get_burstcount(chip);
>> + if (burstcnt < 0) {
>> + dev_err(&chip->dev, "Unable to read burstcount\n");
>> + rc = burstcnt;
>> + goto out_err;
>> }
>>
>> + rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
>> + len - 1, buf);
>> + if (rc < 0)
>> + goto out_err;
>> +
>> /* write last byte */
>> - rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality),
>> buf[count]);
>> + rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[len-
>> 1]);
>> if (rc < 0)
>> goto out_err;
>>
>> --
>> 2.13.3
> This seems to fail reliably with my SPI TPM 2.0. I get EIO when trying to send large amounts of data, e.g. with TPM2_Hash, and subsequent tests seem to take an unusual amount of time. More analysis probably has to wait until November, since I am going to be in Prague next week.

Thanks Alex for testing these.. Did you get the chance to do any further
analysis ?

Thanks & Regards,
       - Nayna

> Alexander
>

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