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powerpc: document the "fsl,ssi-dma-channel" compatible property

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The "fsl,ssi-dma-channel" compatible property is used to specify a DMA channel
on the Freescale Elo DMA controller that should be used exclusively by the
Freescale SSI audio controller.  When a property is marked as such, the Elo
DMA driver will ignore it, and so it will be available for the sound drivers.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
This commit is contained in:
Timur Tabi 2008-10-10 11:52:31 -05:00 committed by Kumar Gala
parent dbe216319f
commit b56c2768d2
2 changed files with 25 additions and 8 deletions
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13
Documentation/powerpc/dts-bindings/fsl/dma.txt
View file

@ -20,7 +20,7 @@ Required properties:
- compatible : compatible list, contains 2 entries, first is
"fsl,CHIP-dma-channel", where CHIP is the processor
(mpc8349, mpc8350, etc.) and the second is
"fsl,elo-dma-channel"
"fsl,elo-dma-channel". However, see note below.
- reg : <registers mapping for channel>
- cell-index : dma channel index starts at 0.
@ -82,7 +82,7 @@ Required properties:
- compatible : compatible list, contains 2 entries, first is
"fsl,CHIP-dma-channel", where CHIP is the processor
(mpc8540, mpc8560, etc.) and the second is
"fsl,eloplus-dma-channel"
"fsl,eloplus-dma-channel". However, see note below.
- cell-index : dma channel index starts at 0.
- reg : <registers mapping for channel>
- interrupts : <interrupt mapping for DMA channel IRQ>
@ -125,3 +125,12 @@ Example:
interrupts = <17 2>;
};
};
Note on DMA channel compatible properties: The compatible property must say
"fsl,elo-dma-channel" or "fsl,eloplus-dma-channel" to be used by the Elo DMA
driver (fsldma). Any DMA channel used by fsldma cannot be used by another
DMA driver, such as the SSI sound drivers for the MPC8610. Therefore, any DMA
channel that should be used for another driver should not use
"fsl,elo-dma-channel" or "fsl,eloplus-dma-channel". For the SSI drivers, for
example, the compatible property should be "fsl,ssi-dma-channel". See ssi.txt
for more information.

12
Documentation/powerpc/dts-bindings/fsl/ssi.txt
View file

@ -24,10 +24,10 @@ Required properties:
"rj-master" - r.j., SSI is clock master
"ac97-slave" - AC97 mode, SSI is clock slave
"ac97-master" - AC97 mode, SSI is clock master
- fsl,playback-dma: phandle to a DMA node for the DMA channel to use for
- fsl,playback-dma: phandle to a node for the DMA channel to use for
playback of audio. This is typically dictated by SOC
design. See the notes below.
- fsl,capture-dma: phandle to a DMA node for the DMA channel to use for
- fsl,capture-dma: phandle to a node for the DMA channel to use for
capture (recording) of audio. This is typically dictated
by SOC design. See the notes below.
@ -51,3 +51,11 @@ playback and DMA channel 1 for capture. SSI2 must use DMA channel 2 for
playback and DMA channel 3 for capture. The developer can choose which
DMA controller to use, but the channels themselves are hard-wired. The
purpose of these two properties is to represent this hardware design.
The device tree nodes for the DMA channels that are referenced by
"fsl,playback-dma" and "fsl,capture-dma" must be marked as compatible with
"fsl,ssi-dma-channel". The SOC-specific compatible string (e.g.
"fsl,mpc8610-dma-channel") can remain. If these nodes are left as
"fsl,elo-dma-channel" or "fsl,eloplus-dma-channel", then the generic Elo DMA
drivers (fsldma) will attempt to use them, and it will conflict with the
sound drivers.