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

Paul Boddie paul at boddie.org.uk
Thu Feb 8 12:42:32 CET 2024

On Thursday, 8 February 2024 12:03:50 CET H. Nikolaus Schaller wrote:
> Indeed. It is a patch "hack: disable DMA for mmc" in feature branch
> letux/jz4730-v12
> https://git.goldelico.com/?p=letux-kernel.git;a=commit;h=bc37b81a83b350a2897
> 604b7e2591863b26673cd
> Otherwise we can't boot the jz4730...

I will eventually revisit the JZ4730 with Linux in this area because I have 
been able to get DMA working on the JZ4730 in my L4Re-based system. I just 
need to demonstrate it working with MMC first, although there may be obvious 
issues in the Linux driver that I might be able to identify already.

I briefly looked at the MMC driver last night, but I didn't get it to do more 
than report initialisation with DMA enabled, as previously shown. Weirdly, if 
I added the vmmc-supply property along with a regulator, it wouldn't report 
initialisation at all, only doing so on MMC1 which didn't have the property 
specified, so I imagine there is something I don't understand about the MMC 
framework. (Again, the documentation is not very helpful, and it also seems 
that voltage-range is supported by some drivers and not others.)

I do wonder if I should check that the clock management is working. That code 
isn't entirely finished because of the different divider computation that the 
X1600 seems to need.


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