dmaengine: dma40: add signal documentation to the device tree bindings

The DMA40 device tree documentation was vague on the second cell passed
in the configuration node for consumers, and did not specify what the
available signals were connected to. Extend the documentation with this
information for the DB8500 ASIC.
Reported-by: Pawel Kulakowski <pawel.kulakowski@tieto.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

Documentation/devicetree/bindings/dma/ste-dma40.txt

@@ -35,9 +35,11 @@ Required properties:
 
 Each dmas request consists of 4 cells:
   1. A phandle pointing to the DMA controller
-  2. Device Type
+  2. Device signal number, the signal line for single and burst requests
+     connected from the device to the DMA40 engine
   3. The DMA request line number (only when 'use fixed channel' is set)
-  4. A 32bit mask specifying; mode, direction and endianness [NB: This list will grow]
+  4. A 32bit mask specifying; mode, direction and endianness
+     [NB: This list will grow]
         0x00000001: Mode:
                 Logical channel when unset
                 Physical channel when set
@@ -54,6 +56,74 @@ Each dmas request consists of 4 cells:
                 Normal priority when unset
                 High priority when set
 
+Existing signal numbers for the DB8500 ASIC. Unless specified, the signals are
+bidirectional, i.e. the same for RX and TX operations:
+
+0:  SPI controller 0
+1:  SD/MMC controller 0 (unused)
+2:  SD/MMC controller 1 (unused)
+3:  SD/MMC controller 2 (unused)
+4:  I2C port 1
+5:  I2C port 3
+6:  I2C port 2
+7:  I2C port 4
+8:  Synchronous Serial Port SSP0
+9:  Synchronous Serial Port SSP1
+10: Multi-Channel Display Engine MCDE RX
+11: UART port 2
+12: UART port 1
+13: UART port 0
+14: Multirate Serial Port MSP2
+15: I2C port 0
+16: USB OTG in/out endpoints 7 & 15
+17: USB OTG in/out endpoints 6 & 14
+18: USB OTG in/out endpoints 5 & 13
+19: USB OTG in/out endpoints 4 & 12
+20: SLIMbus or HSI channel 0
+21: SLIMbus or HSI channel 1
+22: SLIMbus or HSI channel 2
+23: SLIMbus or HSI channel 3
+24: Multimedia DSP SXA0
+25: Multimedia DSP SXA1
+26: Multimedia DSP SXA2
+27: Multimedia DSP SXA3
+28: SD/MM controller 2
+29: SD/MM controller 0
+30: MSP port 1 on DB8500 v1, MSP port 3 on DB8500 v2
+31: MSP port 0 or SLIMbus channel 0
+32: SD/MM controller 1
+33: SPI controller 2
+34: i2c3 RX2 TX2
+35: SPI controller 1
+36: USB OTG in/out endpoints 3 & 11
+37: USB OTG in/out endpoints 2 & 10
+38: USB OTG in/out endpoints 1 & 9
+39: USB OTG in/out endpoints 8
+40: SPI controller 3
+41: SD/MM controller 3
+42: SD/MM controller 4
+43: SD/MM controller 5
+44: Multimedia DSP SXA4
+45: Multimedia DSP SXA5
+46: SLIMbus channel 8 or Multimedia DSP SXA6
+47: SLIMbus channel 9 or Multimedia DSP SXA7
+48: Crypto Accelerator 1
+49: Crypto Accelerator 1 TX or Hash Accelerator 1 TX
+50: Hash Accelerator 1 TX
+51: memcpy TX (to be used by the DMA driver for memcpy operations)
+52: SLIMbus or HSI channel 4
+53: SLIMbus or HSI channel 5
+54: SLIMbus or HSI channel 6
+55: SLIMbus or HSI channel 7
+56: memcpy (to be used by the DMA driver for memcpy operations)
+57: memcpy (to be used by the DMA driver for memcpy operations)
+58: memcpy (to be used by the DMA driver for memcpy operations)
+59: memcpy (to be used by the DMA driver for memcpy operations)
+60: memcpy (to be used by the DMA driver for memcpy operations)
+61: Crypto Accelerator 0
+62: Crypto Accelerator 0 TX or Hash Accelerator 0 TX
+63: Hash Accelerator 0 TX
+
 Example:
 
 	uart@80120000 {