[S] Change in flashrom[main]: ch347_spi: Add spi clock frequency selection

[Nicholas Chin (Code Review)]

Attention is currently required from: Anastasia Klimchuk, ZhiYuanNJ.

Nicholas Chin has posted comments on this change by ZhiYuanNJ. ( https://review.coreboot.org/c/flashrom/+/82776?usp=email )

Change subject: ch347_spi: Add spi clock frequency selection
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Patch Set 7:

(1 comment)

File ch347_spi.c:

https://review.coreboot.org/c/flashrom/+/82776/comment/5aea48e4_45ce6a7b?usp... :
PS7, Line 365: 30MHz
> It seems you are changing the default, why? […]

I don't mind changing the default if it generally works at 30 MHz. I had set it to 15 MHz before as a fairly conservative value as you couldn't easily change it, but that's less of a concern with the ability to change it. That said, I just did some testing and found that a few of my flash chips (Winbond W25Q128JV, Eon EN25QH128A) don't seem to work reliably with the CH347T at 30 MHz, so it might be good to keep it at 15 MHz. The only one that seemed to work reliably was the Macronix MX25L1606E. Sometimes the Winbond chip would work, but when trying to verify it, it would fail, and the differences seemed to be single bit flips. All of those should work at that frequency according to the datasheet, so it's probably some setup/hold time violation. These chips do work with an FT232H programmer I have with a divisor of 2 (30 MHz).