Hi,

Thomas A's advice works on my RPi 4B and is prerequisite for using the
Workstation 32 edition on it. Here is my cookbook:

https://dl.fedoraproject.org/pub/fedora-secondary/development/32/Workstation/aarch64/images/

xzcat ./ | sudo dd status=progress bs=1M of=/dev/sdx && sync

EFI/fedora/grub.cfg
EFI/fedora/grubenv
cma=256M@704M

I end up with an apparenlty fully functional Fedora and after deactivation
of animation effects using Tweaks, Gnome is not (very) sluggish and works
fine for me.

Cheers, Thomas B


On Thu, Apr 23, 2020 at 5:46 PM Thomas H.P. Andersen <[email protected]>
wrote:

> Hi,
>
> I have looked into the CMA setting issue a bit. This is what I have found
> so far.
>
> The rpi4 needs CMA to be in ZONE_DMA (lower 1GB of memory) as this is the
> only area that the peripherals on the rpi4 can address.
>
> The DT sets the allowed range to allocate the CMA from (
> arch/arm/boot/dts/bcm2711.dtsi#L869
> <https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/bcm2711.dtsi#L869>),
> but it seems to not work here. What does work is instead to set the offset
> manually. I replaced "cma=256MB" with "cma=256M@704M" and then it boots.
> Note that it has to be 256M instead of 256MB.
>
> Removing the cma option on the command line was known as a workaround.
> Without that we would fall back to the build config of 64MB cma which was
> located at offset 0x38000000. This left 64MB at the end of ZONE_DMA, and I
> chose offset 704M so that those 64MB would still be free. Not sure if that
> is needed or not. The crashkernel needs to be in ZONE_DMA as well but it
> seems to be set to 0 size.
>
> I have tested on 5.7 rc2 from rawhide.
>
> This probably belongs in a bug report. What would be the correct place to
> file that? From what I can tell upstream has been tested with cma settings
> without problems (as long as the requested CMA size can fit in ZONE_DMA).
> From that it seems like fedora-specific issue. Not sure though.
>
> Cheers,
> Thomas
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