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mfd: cros_ec: spi: Add a DT property to delay asserting the CS

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Some ECs need a little time for waking up before they can accept
SPI data at a high speed. Add a "google,cros-ec-spi-pre-delay"
property to the DT binding to configure this.

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 beginning of a transaction.

Signed-off-by: Alexandru M Stan <amstan@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Alexandru M Stan 2015-06-09 13:04:48 +02:00 committed by Lee Jones
parent 57b33ff077
commit f44c21ff6d
1 changed files with 4 additions and 0 deletions
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4
Documentation/devicetree/bindings/mfd/cros-ec.txt
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@ -18,6 +18,10 @@ Required properties (SPI):
- reg: SPI chip select
Optional properties (SPI):
- google,cros-ec-spi-pre-delay: Some implementations of the EC need a little
time to wake up from sleep before they can receive SPI transfers at a high
clock rate. This property specifies the delay, in usecs, between the
assertion of the CS to the start of the first clock pulse.
- 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