On 5/7/18 9:07 AM, Nayna Jain wrote:
The TPM burstcount and status commands are supposed to return very quickly [2][3]. This patch further reduces the TPM poll sleep time to usecs in get_burstcount() and wait_for_tpm_stat() by calling usleep_range() directly. After this change, performance on a system[1] with a TPM 1.2 with an 8 byte burstcount for 1000 extends improved from ~10.7 sec to ~7 sec. [1] All tests are performed on an x86 based, locked down, single purpose closed system. It has Infineon TPM 1.2 using LPC Bus. [2] From the TCG Specification "TCG PC Client Specific TPM Interface Specification (TIS), Family 1.2": "NOTE : It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take 84 us, which is a long time to stall the CPU. Chipsets may not be designed to post this much data to LPC; therefore, the CPU itself is stalled for much of this time. Sending 1 kB would take 350 μs. Therefore, even if the TPM_STS_x.burstCount field is a high value, software SHOULD be interruptible during this period." [3] From the TCG Specification 2.0, "TCG PC Client Platform TPM Profile (PTP) Specification": "It takes roughly 330 ns per byte transfer on LPC. 256 bytes would take 84 us. Chipsets may not be designed to post this much data to LPC; therefore, the CPU itself is stalled for much of this time. Sending 1 kB would take 350 us. Therefore, even if the TPM_STS_x.burstCount field is a high value, software should be interruptible during this period. For SPI, assuming 20MHz clock and 64-byte transfers, it would take about 120 usec to move 256B of data. Sending 1kB would take about 500 usec. If the transactions are done using 4 bytes at a time, then it would take about 1 msec. to transfer 1kB of data." Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx> Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> ---
Acked-by: Jay Freyensee <why2jjj.linux@xxxxxxxxx>
