[OpenWrt-Devel] mt76x8: Strange GPIO numbering on Onion Omega2+

Lukas Zeller luz at plan44.ch
Sat Jun 12 12:44:34 PDT 2021

Hi Gerd,

> There is still one major issue migrating to 21.02 on my side: Reboot doesn't work. I need to switch power off/on on my Omega2+. AFAIU it has somethoing to do with the SPI 3byte/4byte mode. Older versions worked, but 4byte mode seems to boot faster. BTW: spi-nor spi0.0: mx25l25635e (32768 Kbytes)

This is a hardware problem of the Omega2+ (so further details -> probably off topic for here). But in short: The SPI flash chip must be in 3-byte mode for the MT7688 to start the way CHIP_MODE pins are wired in the Omega2. A power cycle resets the flash to 3 byte mode, however just a SoC reset does not, and if the SPI chip is in 4 byte mode when the reset occurs, the MT7688 will try to boot in 3 byte mode from a chip that is in 4 byte mode. This is only a problem for the 32M flash, as it needs 4-byte addresses. The Omega2 (non +) with 16M flash is thus not affected, it stays in 3 byte mode all the time. See [1] for a hardware solution Onion suggests for the Omega2S+ (the SMT version), which has the flash VDD exposed separately, so this does not work for the THT Omega2+ :-(

Best Regards

[1] https://github.com/OnionIoT/Omega2/blob/master/Documents/Omega2S%20Hardware%20Design%20Guide.pdf
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