On Tue, Sep 10, 2019 at 02:50:35PM +0300, Peter Ujfalusi wrote: > On systems where multiple DMA controllers available, non Slave (for example > memcpy operation) users can not be described in DT as there is no device > involved from the DMA controller's point of view, DMA binding is not usable. > However in these systems still a peripheral might need to be serviced by or > it is better to serviced by specific DMA controller. > When a memcpy is used to/from a memory mapped region for example a DMA in the > same domain can perform better. > For generic software modules doing mem 2 mem operations it also matter that > they will get a channel from a controller which is faster in DDR to DDR mode > rather then from the first controller happen to be loaded. > > This property is inherited, so it may be specified in a device node or in any > of its parent nodes. If a device needs mem2mem dma, I think we should just use the existing dma binding. The provider will need a way to define cell values which mean mem2mem. For generic s/w, it should be able to query the dma speed or get a preferred one IMO. It's not a DT problem. We measure memcpy speeds at boot time to select the fastest implementation for a chip, why not do that for mem2mem DMA? > > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> > --- > .../devicetree/bindings/dma/dma-domain.yaml | 88 +++++++++++++++++++ > 1 file changed, 88 insertions(+) > create mode 100644 Documentation/devicetree/bindings/dma/dma-domain.yaml Note that you have several errors in your schema. Run 'make dt_bindings_check'. Rob
