[PATCH v4 3/6] mtd: spi-nor: cadence-quadspi: Add new binding to enable loop-back circuit

From: Vignesh R
Date: Tue Oct 03 2017 - 01:22:19 EST

Cadence QSPI IP has a adapted loop-back circuit which can be enabled by
setting BYPASS field to 0 in READCAPTURE register. It enables use of
QSPI return clock to latch the data rather than the internal QSPI
reference clock. For high speed operations, adapted loop-back circuit
using QSPI return clock helps to increase data valid window.

Add DT parameter cdns,rclk-en to help enable adapted loop-back circuit
for boards which do have QSPI return clock provided. Update binding
documentation for the same.

Signed-off-by: Vignesh R <vigneshr@xxxxxx>
Acked-by: Rob Herring <robh@xxxxxxxxxx>
Documentation/devicetree/bindings/mtd/cadence-quadspi.txt | 3 +++
1 file changed, 3 insertions(+)

diff --git a/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt b/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
index 7dbe3bd9ac56..bb2075df9b38 100644
--- a/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
+++ b/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
@@ -16,6 +16,9 @@ Required properties:

Optional properties:
- cdns,is-decoded-cs : Flag to indicate whether decoder is used or not.
+- cdns,rclk-en : Flag to indicate that QSPI return clock is used to latch
+ the read data rather than the QSPI clock. Make sure that QSPI return
+ clock is populated on the board before using this property.

Optional subnodes:
Subnodes of the Cadence Quad SPI controller are spi slave nodes with additional