Re: [PATCH v4 3/4] dt-bindings: reserved-memory: Make DMA-BUF CMA heap DT-configurable

Hridya Valsaraju
2021-01-27T20:29:14Z

On Mon, Jan 25, 2021 at 11:07 PM John Stultz <john.stultz@linaro.org> wrote:
>
> On Thu, Jan 21, 2021 at 9:55 AM Minchan Kim <minchan@kernel.org> wrote:
> > .../reserved-memory/dma_heap_chunk.yaml | 56 +++++++++++++++++++
> > 1 file changed, 56 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml b/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
> > new file mode 100644
> > index 000000000000..00db0ae6af61
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/reserved-memory/dma_heap_chunk.yaml
> > @@ -0,0 +1,56 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/reserved-memory/dma_heap_chunk.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Device tree binding for chunk heap on DMA HEAP FRAMEWORK
> > +
> > +description: |
> > + The DMA chunk heap is backed by the Contiguous Memory Allocator (CMA) and
> > + supports bulk allocation of fixed size pages.
> > +
> > +maintainers:
> > + - Hyesoo Yu <hyesoo.yu@samsung.com>
> > + - John Stultz <john.stultz@linaro.org>
> > + - Minchan Kim <minchan@kernel.org>
> > + - Hridya Valsaraju<hridya@google.com>
> > +
> > +
> > +properties:
> > + compatible:
> > + enum:
> > + - dma_heap,chunk
> > +
> > + chunk-order:
> > + description: |
> > + order of pages that will get allocated from the chunk DMA heap.
> > + maxItems: 1
> > +
> > + size:
> > + maxItems: 1
> > +
> > + alignment:
> > + maxItems: 1
> > +
> > +required:
> > + - compatible
> > + - size
> > + - alignment
> > + - chunk-order
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + reserved-memory {
> > + #address-cells = <2>;
> > + #size-cells = <1>;
> > +
> > + chunk_memory: chunk_memory {
> > + compatible = "dma_heap,chunk";
> > + size = <0x3000000>;
>
> Hey Minchan,
> Looking closer here, would it make more sense to document the "reg =
> <>" parameter here as well instead of just "size = <>"?
>
> That way the address of the region could be explicitly specified (for
> instance, to ensure the CMA region created is 32bit addressable). And
> more practically, trying to satisfy the base address alignment checks
> in the final patch when its set dynamically may require a fair amount
> of luck - I couldn't manage it in my own testing on the hikey960 w/o
> resorting to reg= :)
>
> It does look like the RESERVEDMEM_OF_DECLARE() logic already supports
> this, so it's likely just a matter of documenting it here?

Thank you John, yes, that makes sense. We will add the 'reg' parameter
as well when we send out the next version.

Regards,
Hridya

>
> thanks
> -john