Re: [PATCH v1 3/5] dt-bindings: Add DT bindings for NVIDIA Tegra AHB DMA controller
From: Jon Hunter <jonathanh@nvidia.com>
Date: 2017-09-27 13:48:05
Also in:
linux-clk, linux-tegra, lkml
On 27/09/17 14:44, Jon Hunter wrote:
On 27/09/17 13:12, Dmitry Osipenko wrote:quoted
On 27.09.2017 11:34, Jon Hunter wrote:quoted
On 27/09/17 02:57, Dmitry Osipenko wrote:quoted
On 26.09.2017 17:50, Jon Hunter wrote:quoted
On 26/09/17 00:22, Dmitry Osipenko wrote:quoted
Document DT bindings for NVIDIA Tegra AHB DMA controller that presents on Tegra20/30 SoC's. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- .../bindings/dma/nvidia,tegra20-ahbdma.txt | 23 ++++++++++++++++++++++ 1 file changed, 23 insertions(+) create mode 100644 Documentation/devicetree/bindings/dma/nvidia,tegra20-ahbdma.txtdiff --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.TRM shows the following in the APBDMA_TRIG_REG_0 ... "XRQ_A: XRQ.A (GPIOA) (Hardware initiated DMA request)"
Furthermore there are timer and hw-semaphore triggers as well. Jon -- nvpublic