[v2,3/5] mtd: spi-nor: cadence-quadspi: Add new binding to enable loop-back circuit

Message ID 20170816045053.15492-4-vigneshr@ti.com
State Superseded
Delegated to: Cyrille Pitchen
Headers show

Commit Message

Vignesh R Aug. 16, 2017, 4:50 a.m.
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@ti.com>
---
 Documentation/devicetree/bindings/mtd/cadence-quadspi.txt | 3 +++
 1 file changed, 3 insertions(+)

Comments

Rob Herring Aug. 17, 2017, 10 p.m. | #1
On Wed, Aug 16, 2017 at 10:20:51AM +0530, Vignesh R wrote:
> 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@ti.com>
> ---
>  Documentation/devicetree/bindings/mtd/cadence-quadspi.txt | 3 +++
>  1 file changed, 3 insertions(+)

Acked-by: Rob Herring <robh@kernel.org>

Patch

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