Re: [PATCH v3 2/3] arm64: dts: Add APM X-Gene DMA device and DMA clock DTS nodes

[Arnd Bergmann]

On Monday 19 January 2015 18:11:08 Rameshwar Prasad Sahu wrote:
> diff --git a/arch/arm64/boot/dts/apm/apm-storm.dtsi b/arch/arm64/boot/dts/apm/apm-storm.dtsi
> index f1ad9c2..e20da23 100644
> --- a/arch/arm64/boot/dts/apm/apm-storm.dtsi
> +++ b/arch/arm64/boot/dts/apm/apm-storm.dtsi
> @@ -103,6 +103,9 @@
>                 #size-cells = <2>;
>                 ranges;
> 
> +               /* DDR range is 42-bit addressing */
> +               dma-ranges = <0x40 0x0 0x40 0x0 0x1ff 0xffffffff>;
> +
> 

The comment above is misleading, and the value is wrong. I assume you
copied these from the AMD patch that introduced the respective property.

The value should be

	dma-ranges = <0x40 0x0 0x40 0x0 0x200 0>;

to say that any DMA to physical addresses from 0 to 0x3f.ffffffff
is disallowed and dma to physical addresses from 0x40.00000000
to 0x23f.ffffffff is allowed and gets translated using an
identity mapping.

I also see that on Mustang, all memory is outside of this range,
which is a bit suspicious, while your PCI memory space is
included.

It would be best to match the numbers up with your data sheet.

	Arnd
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