On 10/06/2015 03:16 AM, Jon Hunter wrote:
On 05/10/15 14:12, Mark Rutland wrote:
On Mon, Oct 05, 2015 at 01:10:06PM +0100, Jon Hunter wrote:
Add device-tree binding documentation for the Tegra210 Audio DMA
controller.
Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
---
.../devicetree/bindings/dma/tegra210-adma.txt | 63 ++++++++++++++++++++++
1 file changed, 63 insertions(+)
create mode 100644 Documentation/devicetree/bindings/dma/tegra210-adma.txt
diff --git a/Documentation/devicetree/bindings/dma/tegra210-adma.txt b/Documentation/devicetree/bindings/dma/tegra210-adma.txt
new file mode 100644
index 000000000000..df0e46868a63
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/tegra210-adma.txt
@@ -0,0 +1,63 @@
+* NVIDIA Tegra Audio DMA (ADMA) controller
+
+Required properties:
+- compatible: Must be "nvidia,tegra210-adma".
+- reg: Should contain DMA registers location and length. This should be
+ a single entry that includes all of the per-channel registers in one
+ contiguous bank.
+- interrupt-parent: Phandle to the interrupt parent controller.
+- interrupts: Should contain all of the per-channel DMA interrupts in
+ ascending order with respect to the DMA channel index.
+- clocks: Must contain one entry for the ADMA module clock, "adma_ape".
+- clock-names: Must contain the entry "adma_ape".
+- dma-channels: Must be 22. Defines the number of DMA channels supported
+ by the DMA controller.
If this has to be a fixed value, why is it necessary? Why does the
driver not just know this?
Are there other instances of this IP block where this differs?
So this will change for future devices and yes it may seem silly now to
have something that fixed and appears to be constant but I was trying to
future proof the binding. May be the comment should read "For tegra210
must be 22", however, I thought the compatible string would imply this.
Typically you'd want a table in the driver that maps from compatible
value to the set of per-SoC data that's associated with the compatible
value. Then, you don't need to put this data into the DT.
Even if you don't want to do that (e.g. so the driver can work on future
HW without code changes), then you can always add this property in the
future if needed; if the property is present the value in it will be
used, but if missing, any driver should default to the value in use
for/on HW before the binding update.
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