Power & Source of Big Ideas

Technically they both do already, it's just a matter of a suitable devtree.
I find things can be a bit tricky at higher (1.5M) bitrates, and it generally seems to be down to the chip on the adapter. Avoid Prolific PL2303 (almost all of them are clones which don't work very well at the higher rate) and FTDI (ditto, and FTDI can eat a bag of dicks). SiL CP2102 or CP2104 based...
Yup, for u-boot check out doc/README.rockchip. The instructions are a bit sparse for the RK3328, but pretend it's an RK3399 and you're most of the way there. You'll want "option 3" (i.e. with TPL).
Ah, I've SPI flash working just fine now. Apparently DMA support (ARM PL330) is essential for correct (well, any) operation of the Rockchip SPI driver. Whoops! I haven't tried booting off of it yet. For anyone curious, here's what my devtree entry looks like: &spi0 { spiflash@0 { #address-cells ...
According to the schematic the intended part is a Macronix MX25L12835F. I've tried with a Winbond W25Q128FV (which should be compatible) without any success. This includes what should be the correct devtree entry.
vanarebane wrote:
Quite the disappointment to buy a board for GPIO and see there is no support for it

I can't speak for the official distribution, but GPIO works absolutely fine from the mainline.