On Thu, Jan 21, 2021 at 09:55:01AM -0800, Minchan Kim wrote: > From: Hyesoo Yu <hyesoo.yu@xxxxxxxxxxx> > > Document devicetree binding for chunk cma heap on dma heap framework. > > The DMA chunk heap supports the bulk allocation of higher order pages. > > The chunk heap's allocator allocates from the CMA area. It is optimized > to perform bulk allocation of higher order pages in an efficient manner. > For this purpose, the heap needs an exclusive CMA area that will only be > used for allocation by the heap. This is the reason why we need to use > the DT to create and configure a reserved memory region for use by the > chunk CMA heap driver. Since all allocation from DMA-BUF heaps happen > from the user-space, there is no other appropriate device-driver that > we can use to register the chunk CMA heap and configure the reserved > memory region for its use. LWN tells me we don't need carve outs any more[1]: "CMA now relies on compaction and no longer uses a carved-out memory region." So why do we need this? [1] https://lwn.net/Articles/839216/ > > Signed-off-by: Hyesoo Yu <hyesoo.yu@xxxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > Signed-off-by: Hridya Valsaraju <hridya@xxxxxxxxxx> > --- > .../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@xxxxxxxxxxx> > + - John Stultz <john.stultz@xxxxxxxxxx> > + - Minchan Kim <minchan@xxxxxxxxxx> > + - Hridya Valsaraju<hridya@xxxxxxxxxx> > + > + > +properties: > + compatible: > + enum: > + - dma_heap,chunk Convention is vendor,thing and 'dma_heap' is not a vendor. Also, '-' is preferred over '_'. > + > + chunk-order: > + description: | > + order of pages that will get allocated from the chunk DMA heap. Page size depends on Linux configuration. And 'order' is very much a Linuxism. > + 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>; > + alignment = <0x0 0x00010000>; > + chunk-order = <4>; > + }; > + }; > -- > 2.30.0.296.g2bfb1c46d8-goog >
