Add check for generic compatible string exported by current u-boot.

Taking this over so I can publish some additions/changes...

Overall this is looking good to me. The core clock logic seems right, as well as the SYS group. I did not verify the clock hierarchy in detail compared to the TRM.

In D44434#1013418, @bz wrote:

Thank you!
Can we also adjust the comment above MPASS() in the header file?

Handle minor review feedback.

Trim #includes; fix softc size in driver declaration.

This, and the preceding changes are not super impactful. I'm just trying to lay the groundwork to make the testing/upstreaming process simpler (mainly for myself).

In D34118#1000839, @jhb wrote:

This is ok, but I do think it's not ideal, per se. I think to make bounce pages more packed you would not apply this diff but instead do something like:

...

In D34118#771586, @jhb wrote:

I would say that a max segment size < PAGE_SIZE is generally under-tested and probably broken in several ways. I would be tempted to still copy PAGE_SIZE chunks into bounce pages when needed and then carve the PAGE_SIZE segments up into multiple segments when writing out the segments if possible.

Rebase and extend the patch to other architectures.

In D43849#1000490, @karels wrote:

Is the following summary accurate: This change is not required for all systems, but doesn't hurt; it makes it easier for some configurations. If that's true, then I don't have a problem with it.

In D43849#1000412, @jrtc27 wrote:

I just flashed the firmware to the VisionFive 2's on-board flash and then booted the existing GENERICSD without touching partitioning.