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authorSowjanya Komatineni <skomatineni@nvidia.com>2019-04-04 17:14:18 -0700
committerMark Brown <broonie@kernel.org>2019-04-08 14:21:45 +0700
commit7558f978f9b66a2bc284a0e8c0764b88305bc29f (patch)
treed7037c99641363dca542f73da8839313e4d1aeb3
parentf1ca9992ced71029735784de138f53446363087f (diff)
downloadlinux-7558f978f9b66a2bc284a0e8c0764b88305bc29f.tar.bz2
spi: document tx/rx clock delay properties
Tegra SPI controller has TX and RX trimmers to tuning the delay of SPI master clock with respect to the data. TX and RX tap values are based on the platform validation across the PVT and the trimmer values vary based on the trace lengths to the corresponding SPI devices. Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com> Signed-off-by: Mark Brown <broonie@kernel.org>
-rw-r--r--Documentation/devicetree/bindings/spi/nvidia,tegra114-spi.txt20
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/spi/nvidia,tegra114-spi.txt b/Documentation/devicetree/bindings/spi/nvidia,tegra114-spi.txt
index 9ba7c5a273b4..db8e0d71c5bc 100644
--- a/Documentation/devicetree/bindings/spi/nvidia,tegra114-spi.txt
+++ b/Documentation/devicetree/bindings/spi/nvidia,tegra114-spi.txt
@@ -23,6 +23,18 @@ Required properties:
Recommended properties:
- spi-max-frequency: Definition as per
Documentation/devicetree/bindings/spi/spi-bus.txt
+Optional properties:
+- nvidia,tx-clk-tap-delay: Delays the clock going out to the external device
+ with this tap value. This property is used to tune the outgoing data from
+ Tegra SPI master with respect to outgoing Tegra SPI master clock.
+ Tap values vary based on the platform design trace lengths from Tegra SPI
+ to corresponding slave devices. Valid tap values are from 0 thru 63.
+- nvidia,rx-clk-tap-delay: Delays the clock coming in from the external device
+ with this tap value. This property is used to adjust the Tegra SPI master
+ clock with respect to the data from the SPI slave device.
+ Tap values vary based on the platform design trace lengths from Tegra SPI
+ to corresponding slave devices. Valid tap values are from 0 thru 63.
+
Example:
spi@7000d600 {
@@ -38,4 +50,12 @@ spi@7000d600 {
reset-names = "spi";
dmas = <&apbdma 16>, <&apbdma 16>;
dma-names = "rx", "tx";
+ <spi-client>@<bus_num> {
+ ...
+ ...
+ nvidia,rx-clk-tap-delay = <0>;
+ nvidia,tx-clk-tap-delay = <16>;
+ ...
+ };
+
};