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

[Paul Boddie]

On Sunday, 11 February 2024 17:26:34 CET H. Nikolaus Schaller wrote:
> 
> What I assume is that 1-bit mode may run generally slower or some cards
> may be more robust to overclocking in 1-bit mode than in 4 bit mode (where
> e.g. alignment of 4 data bits to a clock line must be guaranteed).
> 
> Since I have everything working well in 4 bit mode just with slower clock we
> can IMHO focus on the clock setup now.

Well, I just managed to fix a mistake I had made sending application-specific 
commands to the card, so I can now select 4-bit mode. This is in my own 
software framework that I am using for testing and investigation.

What I can report is that since I am not changing the clock configuration for 
MSC0, thus leaving it as U-Boot left it, it is supposedly running at 50MHz. 
For initialisation, I divide the device clock by 128 to yield 390.625kHz for 
the bus clock, which is close to the recommended 400kHz. Then, for transfers I 
have been testing with a divider of 2, which is the suggested 25MHz for a card 
of the type you sent me.

So, in principle, all of this should work in Linux, but I imagine that I need 
to review the CGU code and make sure it works as it should.

Paul