[S] Change in flashrom[main]: udelay: clock_getres() does not provide clock_gettime() resolution

[Hsuan-ting Chen (Code Review)]

Attention is currently required from: Brian Norris, Stefan Reinauer.

Hsuan-ting Chen has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/80806?usp=email )

The change is no longer submittable: All-Comments-Resolved is unsatisfied now.

Change subject: udelay: clock_getres() does not provide clock_gettime() resolution
......................................................................

Patch Set 1:

(2 comments)

Patchset:

PS1: 
I'd like to note that I tested on several ChromeOS devices: 1. MTK (ARM) and 2. Intel Apollo Lake.

Our clock sources (arch_sys_counter on ARM and tsc on Intel) are reliable and do not require additional calibration in flashrom. Therefore, I believe removing the calibration will not cause issues on ChromeOS.

I'm also aware that not all clock sources are trustworthy. For example, using acpi_pm on Intel platforms can lead to significantly larger errors in clock_usec_delay. (But it is still tolerable)

So from ChromeOS's perspect, I would think this change should be good to go. But I have no sufficient knowledge for any other devices

File udelay.c:

https://review.coreboot.org/c/flashrom/+/80806/comment/a73a3c25_1fe1068e :
PS1, Line 120: {
(This comment is copied from my comment in CHROMIUM repo)

What about add a comment here:

// We assume clock_gettime() provides sufficient precision; avoid unnecessary calibration overhead.