On 27.09.2017 11:34, Jon Hunter wrote: > > On 27/09/17 02:57, Dmitry Osipenko wrote: >> On 26.09.2017 17:50, Jon Hunter wrote: >>> >>> On 26/09/17 00:22, Dmitry Osipenko wrote: >>>> Document DT bindings for NVIDIA Tegra AHB DMA controller that presents >>>> on Tegra20/30 SoC's. >>>> >>>> Signed-off-by: Dmitry Osipenko <dig...@gmail.com> >>>> --- >>>> .../bindings/dma/nvidia,tegra20-ahbdma.txt | 23 >>>> ++++++++++++++++++++++ >>>> 1 file changed, 23 insertions(+) >>>> create mode 100644 >>>> Documentation/devicetree/bindings/dma/nvidia,tegra20-ahbdma.txt >>>> >>>> diff --git >>>> a/Documentation/devicetree/bindings/dma/nvidia,tegra20-ahbdma.txt >>>> b/Documentation/devicetree/bindings/dma/nvidia,tegra20-ahbdma.txt >>>> new file mode 100644 >>>> index 000000000000..2af9aa76ae11 >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/dma/nvidia,tegra20-ahbdma.txt >>>> @@ -0,0 +1,23 @@ >>>> +* NVIDIA Tegra AHB DMA controller >>>> + >>>> +Required properties: >>>> +- compatible: Must be "nvidia,tegra20-ahbdma" >>>> +- reg: Should contain registers base address and length. >>>> +- interrupts: Should contain one entry, DMA controller interrupt. >>>> +- clocks: Should contain one entry, DMA controller clock. >>>> +- resets : Should contain one entry, DMA controller reset. >>>> +- #dma-cells: Should be <1>. The cell represents DMA request select >>>> value >>>> + for the peripheral. For more details consult the Tegra TRM's >>>> + documentation, in particular AHB DMA channel control register >>>> + REQ_SEL field. >>> >>> What about the TRIG_SEL field? Do we need to handle this here as well? >>> >> >> Actually, DMA transfer trigger isn't related a hardware description. It's up >> to >> software to decide what trigger to select. So it shouldn't be in the binding. > > I think it could be, if say a board wanted a GPIO to trigger a transfer. >
GPIO isn't a very good example, there is no "GPIO" trigger. To me all triggers are software-defined, so that software could create transfer chains. >> And I think the same applies to requester... any objections? > > Well, the REQ_SEL should definitely be in the binding. > Okay. > Laxman, Stephen, what are your thoughts on the TRIG_SEL field? Looks > like we never bothered with it for the APB DMA and so maybe no ones uses > this. > -- Dmitry
