dt-bindings: dmaengine: xilinx_dma: Add xlnx,irq-delay property

Add an optional AXI DMA property 'xlnx,irq-delay'. It specifies interrupt
timeout value and causes the DMA engine to generate an interrupt after the
delay time period has expired. Timer begins counting at the end of a packet
and resets with receipt of a new packet or a timeout event occurs.

This property is useful when AXI DMA is connected to the streaming IP i.e
axiethernet where inter packet latency is critical while still taking the
benefit of interrupt coalescing.

Signed-off-by: Radhey Shyam Pandey <[email protected]>
Acked-by: Rob Herring <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: Radhey Shyam Pandey

Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt

@@ -52,7 +52,9 @@ Optional properties for AXI DMA and MCDMA:
 
 Optional properties for AXI DMA:
 - xlnx,axistream-connected: Tells whether DMA is connected to AXI stream IP.
-
+- xlnx,irq-delay: Tells the interrupt delay timeout value. Valid range is from
+	0-255. Setting this value to zero disables the delay timer interrupt.
+	1 timeout interval = 125 * clock period of SG clock.
 Optional properties for VDMA:
 - xlnx,flush-fsync: Tells which channel to Flush on Frame sync.
 	It takes following values: