On Thursday 18 April 2013, Lee Jones wrote:
> Using the new DMA DT bindings and API, we can register the DMA40 driver
> as Device Tree capable. Now, when a client attempts to allocate a
> channel using the DMA DT bindings via its own node, we are able to parse
> the request and allocate a channel in the correct manor.
s/manor/manner/ ?
> +Optional properties:
> +- interrupt-parent: Should be the phandle for the interrupt controller
> + that services interrupts for this device
I would not bother listing the interrupt-parent.
> +Clients
> +Required properties:
> +- dmas: Comma seperated list of dma channel requests
> +- dma-names: Names of the aforementioned requested channels
> +
> +Each dmas request consists of 4 cells:
> + 1. A phandle pointing to the DMA controller
> + 2. The DMA request line number (only when 'use fixed channel' is set)
> + 3. Device Type
> + 4. A 32bit mask specifying; mode, direction and endianess [NB: This list
> will grow]
> + bits 1-2: Mode:
> + 00: Logical
> + 01: Physical
> + 10: Operation
> + 11: Undefined - will most likely return an error
The statement "will most likely return an error" is not very
specification-like. ;-) Maybe better call it "reserved".
What is actually an "Operation" channel? Do we need it for slaves?
> + bits 3-4: Direction:
> + 00: Mem to Mem
> + 01: Mem to Dev
> + 10: Dev to Mem
> + 11: Dev to Dev
For slave channels, we only need mem-to-dev and dev-to-mem, so I would
use only one bit here.
> + bit 5: Endianess:
> + 0: Little endian
> + 1: Big endian
> + bit 6: Use fixed channel:
> + 0: Use automatic channel selection
> + 1: Use DMA request line number
I think you have mixed up the "device type" and "request line number".
The request line is what identifies the slave device (which you call
the device type), and I would put that number first.
Arnd
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