On 06/10/15 23:57, Stephen Warren wrote: > 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. Yes I have seen that which I was not sure that I was a fan of, given that we have DT and its purpose is to describe the hardware. So may be the problem I have is deciding on which hardware parameters should be described in DT versus those that should be place in the driver itself. I am not sure if there is a rule of thumb for this type of thing? Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
