[Letux-kernel] X1600 / LX16 support - here: adding MMC - MAJOR BREAKTHROUGH

[Paul Boddie]

On Sunday, 11 February 2024 08:50:53 CET H. Nikolaus Schaller wrote:
> 
> So the main factor is indeed the SD card speed (and clock calculations).
> Reduced bus width may work with some SD cards and X1600 unit.

Yesterday, I found that switching to 1-bit bus width allowed data transfers to 
finally work. I aim to investigate 4-bit mode today, which should be supported 
by SD cards, but I imagine that it is more complicated than it appears.

For instance, a command is needed to set the bus width on SD cards: they start 
out in 1-bit mode and need to be told to switch to 4-bit mode. It isn't enough 
to tell the SoC to use 4-bit mode, but I suppose the Linux framework knows 
about this already.

Paul