On Mon, Nov 18, 2013 at 11:48:10AM +0000, Mark Rutland wrote: > On Mon, Nov 18, 2013 at 10:30:47AM +0000, Thierry Reding wrote: > > From: Rhyland Klein <[email protected]> > > > > 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 <[email protected]> > > Reviewed-by: Bernie Thompson <[email protected]> > > Reviewed-by: Andrew Bresticker <[email protected]> > > Cc: Rob Herring <[email protected]> > > Cc: Pawel Moll <[email protected]> > > Cc: Mark Rutland <[email protected]> > > Cc: Ian Campbell <[email protected]> > > Signed-off-by: Thierry Reding <[email protected]> > > --- > > Documentation/devicetree/bindings/mfd/cros-ec.txt | 4 +++ > > drivers/mfd/cros_ec_spi.c | 30 > > +++++++++++++++++++++++ > > 2 files changed, 34 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt > > b/Documentation/devicetree/bindings/mfd/cros-ec.txt > > index 5f229c5f6da9..fb3034a87ae0 100644 > > --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt > > +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt > > @@ -17,6 +17,10 @@ Required properties (SPI): > > - compatible: "google,cros-ec-spi" > > - reg: SPI chip select > > > > +Optional properties (SPI): > > +- google,cros-ec-spi-msg-delay: This property is how long of a delay, in > > usecs, > > + to use on the last transfer of a message, to force time between > > transactions. > > + > > Lose the "This property is", that's obvious from the structure of the > document.
Will do. > It would be nice to have an explanation in the binding document as to > _why_ you might want to do this (e.g. the HW expects the rising edge to > come some number of uS after the data, if it comes too early it > explodes). From what I can tell, this might differ on the exact variant of the EC, but generally it seems that when the interval between two transactions isn't long enough the EC won't be able to respond properly in time and cause subsequent transactions to hang. Perhaps Rhyland, Bernie or Andrew are more familiar with the details and therefore can provide a better or more accurate explanation. > Otherwise this looks fine to me. Thanks, Thierry
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