Re: [RFC PATCH 1/5] dt-bindings: dma: Add CMA Heap bindings

Florent Tomasin
2025-02-12T10:47:06Z

On 12/02/2025 10:01, Maxime Ripard wrote:
> On Wed, Feb 12, 2025 at 09:49:56AM +0000, Florent Tomasin wrote:
>> Note that the CMA patches were initially shared to help reproduce my
>> environment of development, I can isolate them in a separate patch
>> series and include a reference or "base-commit:" tag to it in the
>> Panthor protected mode RFC, to help progress this review in another
>> thread. It will avoid overlapping these two topics:
>>
>> - Multiple standalone CMA heaps support
>> - Panthor protected mode handling
>
> You keep insisting on using CMA here, but it's really not clear to me
> why you would need CMA in the first place.
>
> By CMA, do you mean the CMA allocator, and thus would provide buffers
> through the usual dma_alloc_* API, or would any allocator providing
> physically contiguous memory work?

You are correct only the CMA allocator is relevant. I needed a way to
sub-allocate from a carved-out memory.

> In the latter case, would something like this work:
> https://lore.kernel.org/all/20240515-dma-buf-ecc-heap-v1-1-54cbbd049511@kernel.org/

Thanks for sharing this link, I was not aware previous work was done
on this aspect. The new carveout heap introduced in the series could
probably be a good alternative. I will play-around with it and share
some updates.

Appreciated,
Florent