path: root/Documentation
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authorRhyland Klein <rklein@nvidia.com>2013-12-09 12:36:09 +0100
committerLee Jones <lee.jones@linaro.org>2014-01-21 08:28:06 +0000
commit01e73c89cf03c020e586dc9e30d52a6e098853f6 (patch)
treedaef78c50110f4fed3218742bf8c6560e3645639 /Documentation
parentdaf93d2287ff8eb4a2f28224275fb02d623df2ab (diff)
mfd: cros ec: spi: Add delay for raising CS
The EC has specific timing it requires. Add support for an optional delay after raising CS to fix timing issues. This is configurable based on a DT property "google,cros-ec-spi-msg-delay". If this property isn't set, then no delay will be added. However, if set it will cause a delay equal to the value passed to it to be inserted at the end of a transaction. Signed-off-by: Rhyland Klein <rklein@nvidia.com> Reviewed-by: Bernie Thompson <bhthompson@chromium.org> Reviewed-by: Andrew Bresticker <abrestic@chromium.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Lee Jones <lee.jones@linaro.org>
Diffstat (limited to 'Documentation')
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
index 5f229c5f6da9..8009c3d87f33 100644
--- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
+++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
@@ -17,6 +17,15 @@ Required properties (SPI):
- compatible: "google,cros-ec-spi"
- reg: SPI chip select
+Optional properties (SPI):
+- google,cros-ec-spi-msg-delay: Some implementations of the EC require some
+ additional processing time in order to accept new transactions. If the delay
+ between transactions is not long enough the EC may not be able to respond
+ properly to subsequent transactions and cause them to hang. This property
+ specifies the delay, in usecs, introduced between transactions to account
+ for the time required by the EC to get back into a state in which new data
+ can be accepted.
Required properties (LPC):
- compatible: "google,cros-ec-lpc"
- reg: List of (IO address, size) pairs defining the interface uses