linux/Documentation/devicetree/bindings/powerpc/fsl/ssi.txt
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   1Freescale Synchronous Serial Interface
   2
   3The SSI is a serial device that communicates with audio codecs.  It can
   4be programmed in AC97, I2S, left-justified, or right-justified modes.
   5
   6Required properties:
   7- compatible:       Compatible list, contains "fsl,ssi".
   8- cell-index:       The SSI, <0> = SSI1, <1> = SSI2, and so on.
   9- reg:              Offset and length of the register set for the device.
  10- interrupts:       <a b> where a is the interrupt number and b is a
  11                    field that represents an encoding of the sense and
  12                    level information for the interrupt.  This should be
  13                    encoded based on the information in section 2)
  14                    depending on the type of interrupt controller you
  15                    have.
  16- interrupt-parent: The phandle for the interrupt controller that
  17                    services interrupts for this device.
  18- fsl,mode:         The operating mode for the SSI interface.
  19                    "i2s-slave" - I2S mode, SSI is clock slave
  20                    "i2s-master" - I2S mode, SSI is clock master
  21                    "lj-slave" - left-justified mode, SSI is clock slave
  22                    "lj-master" - l.j. mode, SSI is clock master
  23                    "rj-slave" - right-justified mode, SSI is clock slave
  24                    "rj-master" - r.j., SSI is clock master
  25                    "ac97-slave" - AC97 mode, SSI is clock slave
  26                    "ac97-master" - AC97 mode, SSI is clock master
  27- fsl,playback-dma: Phandle to a node for the DMA channel to use for
  28                    playback of audio.  This is typically dictated by SOC
  29                    design.  See the notes below.
  30- fsl,capture-dma:  Phandle to a node for the DMA channel to use for
  31                    capture (recording) of audio.  This is typically dictated
  32                    by SOC design.  See the notes below.
  33- fsl,fifo-depth:   The number of elements in the transmit and receive FIFOs.
  34                    This number is the maximum allowed value for SFCSR[TFWM0].
  35- fsl,ssi-asynchronous:
  36                    If specified, the SSI is to be programmed in asynchronous
  37                    mode.  In this mode, pins SRCK, STCK, SRFS, and STFS must
  38                    all be connected to valid signals.  In synchronous mode,
  39                    SRCK and SRFS are ignored.  Asynchronous mode allows
  40                    playback and capture to use different sample sizes and
  41                    sample rates.  Some drivers may require that SRCK and STCK
  42                    be connected together, and SRFS and STFS be connected
  43                    together.  This would still allow different sample sizes,
  44                    but not different sample rates.
  45
  46Optional properties:
  47- codec-handle:     Phandle to a 'codec' node that defines an audio
  48                    codec connected to this SSI.  This node is typically
  49                    a child of an I2C or other control node.
  50
  51Child 'codec' node required properties:
  52- compatible:       Compatible list, contains the name of the codec
  53
  54Child 'codec' node optional properties:
  55- clock-frequency:  The frequency of the input clock, which typically comes
  56                    from an on-board dedicated oscillator.
  57
  58Notes on fsl,playback-dma and fsl,capture-dma:
  59
  60On SOCs that have an SSI, specific DMA channels are hard-wired for playback
  61and capture.  On the MPC8610, for example, SSI1 must use DMA channel 0 for
  62playback and DMA channel 1 for capture.  SSI2 must use DMA channel 2 for
  63playback and DMA channel 3 for capture.  The developer can choose which
  64DMA controller to use, but the channels themselves are hard-wired.  The
  65purpose of these two properties is to represent this hardware design.
  66
  67The device tree nodes for the DMA channels that are referenced by
  68"fsl,playback-dma" and "fsl,capture-dma" must be marked as compatible with
  69"fsl,ssi-dma-channel".  The SOC-specific compatible string (e.g.
  70"fsl,mpc8610-dma-channel") can remain.  If these nodes are left as
  71"fsl,elo-dma-channel" or "fsl,eloplus-dma-channel", then the generic Elo DMA
  72drivers (fsldma) will attempt to use them, and it will conflict with the
  73sound drivers.
  74