Re: cma can't activate area on arm64

On Fri, 2020-02-28 at 11:56 -0800, Jonathan Richardson wrote:

This is stingray (arch/arm64/boot/dts/broadcom/stingray/bcm958742k.dts).
cma is specified on cmdline as "cma=1G". The full boot log was in the
attachment.

Would you mind attaching it again, I was added to the conversation later.

quoted

you use a fixed base? Also, do you want the CMA in ZONE_DMA or
ZONE_DMA32?

I'm not sure which zone we want it in. I'm assuming ZONE_DMA32. Before
that change there was only one zone. If I disable ZONE_DMA I don't see
the error, though I haven't tested anything. I don't really understand why
ZONE_DMA is enabled by default if it's a requirement for Rpi only.
I'm assuming it should work as is with both zones enabled but not clear how
cma spans the two zones. Was there a reason for having both zones enabled as
the default?

It's enabled by default to be able to boot all boards with a common kernel
image.

IIRC the allocation algo for CMA placement tries to fit it as high as possible
in ZONE_DMA32, but I can't really say much more without the logs.

Regards,
Nicolas