[coreboot-gerrit] [S] Change in coreboot[master]: mb/google/brya: Update Crota's ELAN touchscreen delay to 150 ms

[Paz Zcharya (Code Review)]

Attention is currently required from: Subrata Banik, Terry Chen, Tim Wawrzynczak, Nick Vaccaro, Franklin Lin.

Paz Zcharya has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/68868 )

Change subject: mb/google/brya: Update Crota's ELAN touchscreen delay to 150 ms
......................................................................

Patch Set 6:

(1 comment)

File src/mainboard/google/brya/variants/crota/overridetree.cb:

https://review.coreboot.org/c/coreboot/+/68868/comment/c5bf41cb_1eef071b 
PS6, Line 225: 150
> do we even need 150ms, on Rex, the reset delay with 20ms is meeting the spec.

Spec requires 150 ms minimum delay in between pulling RESET high and sending the first i2c commands. However, in practice, the device (I assume OS) doesn't send commands until about ~2 seconds after the power-on sequence (measured with scope by ELAN).

So the short answer is that we can have 0 delay as long as things don't change. However, if all of a sudden OS' flow changes and we power-on the device late / send commands early (unlikely), things might break.