Re: Aw: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount

Ken Goldman
2017-08-16T19:51:04Z

On 8/14/2017 6:10 AM, Jarkko Sakkinen wrote:
>> Nuvoton, ST Micro, and Infineon confirmed that the TPM empties a byte from
>> the FIFO in under 1 usec. So, even with a static burst count, the entire
>> FIFO would empty in under 10 usec.
>
> Does this break anything lets say in a decade time frame? If it does, I
> will not even consider this. Can you give a definitive answer for that?

My attempt at predicting the future ...

1 - Clock speed should get faster, not slower, so the 1 usec wait state
should get shorter.

2 - TPM buffers should get larger. I'm already reading of 256 byte
buffers. So there should be fewer wait states.

3 - There is a trend toward using the CRB, making the FIFO less applicable.

4 - There is a trend away from LPC connected serial port devices,
printers, and PS/2 mouse and keyboard, and toward USB connected devices.
I assume this will continue, making the already insignificant wait
states irrelevant.