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-rw-r--r--Documentation/devicetree/bindings/spi/sh-msiof.txt16
1 files changed, 15 insertions, 1 deletions
diff --git a/Documentation/devicetree/bindings/spi/sh-msiof.txt b/Documentation/devicetree/bindings/spi/sh-msiof.txt
index bdd83959019c..80710f0f0448 100644
--- a/Documentation/devicetree/bindings/spi/sh-msiof.txt
+++ b/Documentation/devicetree/bindings/spi/sh-msiof.txt
@@ -36,7 +36,21 @@ Required properties:
Optional properties:
- clocks : Must contain a reference to the functional clock.
-- num-cs : Total number of chip-selects (default is 1)
+- num-cs : Total number of chip selects (default is 1).
+ Up to 3 native chip selects are supported:
+ 0: MSIOF_SYNC
+ 1: MSIOF_SS1
+ 2: MSIOF_SS2
+ Hardware limitations related to chip selects:
+ - Native chip selects are always deasserted in
+ between transfers that are part of the same
+ message. Use cs-gpios to work around this.
+ - All slaves using native chip selects must use the
+ same spi-cs-high configuration. Use cs-gpios to
+ work around this.
+ - When using GPIO chip selects, at least one native
+ chip select must be left unused, as it will be
+ driven anyway.
- dmas : Must contain a list of two references to DMA
specifiers, one for transmission, and one for
reception.