overlays: Add Pi 5 version of dwc2

[pelwell]

Most bus masters on Pi 5 have access to at least the lower 4GB, but the old DWC OTG controller is still restricted to the first 1GB. Create a Pi 5-specific version of the overlay including a fragment that ensures the swiotlb bounce buffers are allocated in that area.

This PR replaces #5658.

[pelwell]

@6by9 Can you confirm that this is a suitable alternative to #5658 (if we're nervous about placing unnecessary restrictions on RAM layout for all Pi 5s)?

[timg236]

This seems like a good idea

[6by9]

Should work - I'll double check in a mo.

Is it cleaner to use an include instead of being 50% duplication of dwc2-overlay.dts?

[popcornmix]

Yes, I prefer this solution.

[6by9]

It works to the same level that I had the old "always apply the range" change did.

[pelwell]

Is it cleaner to use an include instead of being 50% duplication of dwc2-overlay.dts?

Much cleaner - done.

[6by9]

Having said this worked, it looks like my system hadn't updated properly :-(

#5658 put a dma-ranges in /, whereas this puts it in /soc.
/soc already has a dma-ranges, and it doesn't get overwritten by the overlay.

[pelwell]

it looks like my system hadn't updated properly :-(

Oh well.

/soc already has a dma-ranges, and it doesn't get overwritten by the overlay.

I would have expected that to be okay, but the dma-ranges above the zone_dma's dma-ranges must be interfering. I'll fix it.

[pelwell]

Fixup pushed. Success looks like this:

$ pi@raspberrypi:~$ dmesg | grep -A3 "Zone ranges"
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000000000-0x000000003fffffff]
[    0.000000]   DMA32    [mem 0x0000000040000000-0x00000000ffffffff]
[    0.000000]   Normal   [mem 0x0000000100000000-0x00000001ffffffff]

[6by9]

Previous patch

pi@bookworm64-rel:~ $ dmesg | grep -A3 "Zone ranges"
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000000000-0x00000000ffffffff]
[    0.000000]   DMA32    empty
[    0.000000]   Normal   [mem 0x0000000100000000-0x00000001ffffffff]

New

pi@bookworm64-rel:~ $ dmesg | grep -A3 "Zone ranges"
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000000000-0x000000003fffffff]
[    0.000000]   DMA32    [mem 0x0000000040000000-0x00000000ffffffff]
[    0.000000]   Normal   [mem 0x0000000100000000-0x00000001ffffffff]

:-)