On 16/09/2019 14.21, Peter Ujfalusi wrote: > > > On 13/09/2019 17.36, Rob Herring wrote: >> 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. > > But isn't it going to be an abuse of the binding? Each DMA controller > would hack this in different ways, probably using out of range DMA > request/trigger number or if they have direction in the binding or some > other parameter would be set to something invalid... > >> 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? > > It would make an impact on boot time since the tests would need to be > done with a large enough copy to be able to see clearly which one is faster. > > Also we should be able to handle different probing orders: > client1 should have mem2mem channel from dma2. > > - dma1 probes > - client1 probes and asks for a mem2mem channel > - dma2 probes > > Here client1 should deffer until dma2 is probed. > > Probably the property should be dma-mem2mem-domain to be more precise on > it's purpose and avoid confusion? Is it OK if I go with dma-mem2mem-domain or dma-mem2mem-controller for v2, but keeping the logic and approach intact? Regards, - Péter > >> >>> >>> 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'. > > That does not do anything on my system, but git dt-doc-validate running > via https://github.com/robherring/yaml-bindings.git. > > - Péter > > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
