[S] Change in coreboot[main]: ec/google/chromeec: Add debug timestamp for host EC commands

[Julius Werner (Code Review)]

Attention is currently required from: Boris Mittelberg, Caveh Jalali, Jayvik Desai, Kapil Porwal, Paul Menzel, Subrata Banik.

Julius Werner has posted comments on this change by Jayvik Desai. ( https://review.coreboot.org/c/coreboot/+/85326?usp=email )

Change subject: ec/google/chromeec: Add debug timestamp for host EC commands
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Patch Set 11:

(1 comment)

File src/ec/google/chromeec/ec_lpc.c:

https://review.coreboot.org/c/coreboot/+/85326/comment/4c3584e1_41590c24?usp... :
PS9, Line 286: printk
> I was thinking we could keep a data structure that maps EC host commands to timestamps. That way, we'd always know which timestamp belongs to which EC host command.

So you would basically be creating hundreds of new timestamps... I don't think this is worth it. I really don't think timestamps are the right tool for this level of debugging anyway.
> We already have a similar feature for FSP. When we build FSP with a specific flag, it adds more timestamps that aren't needed during regular boot.

Okay, but that's a bit of a different situation. The FSP only runs in one specific part of the boot flow and (I think?) there's already a timestamp right before and after it to mark that part. So if you turn on FSP debugging timestamps it's not that surprising that the time between start and end of the FSP is broken up by additional timestamps.

But EC commands happen all over the place, and will change the values for all sorts of timestamps that have nothing to do with the EC.