Re: [PATCH 2/4] spi: Document option to wake a device by toggling CS

From: Geert Uytterhoeven
Date: Thu Jun 30 2016 - 03:12:18 EST


CC devicetree

On Thu, Jun 30, 2016 at 5:54 AM, <apronin@xxxxxxxxxxxx> wrote:
> From: Andrey Pronin <apronin@xxxxxxxxxxxx>
>
> Some SPI devices may go to sleep after a period of inactivity
> on SPI. For such devices, if enough time has passed since the
> last SPI transaction, toggle CS and wait for the device to
> start before communicating with it.
>
> Signed-off-by: Andrey Pronin <apronin@xxxxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/spi/spi-bus.txt | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
> index 42d5954..1b7ffd4 100644
> --- a/Documentation/devicetree/bindings/spi/spi-bus.txt
> +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
> @@ -63,6 +63,13 @@ contain the following properties.
> used for MISO. Defaults to 1 if not present.
> - spi-rx-delay-us - (optional) Microsecond delay after a read transfer.
> - spi-tx-delay-us - (optional) Microsecond delay after a write transfer.
> +- cs-wake-after-sleep - (optional) Device may go to sleep after a period
> + of SPI inactivity. If this flag is set, toggle CS and
> + wait for it to wake before communicating to it.
> +- cs-sleep-delay - (optional) Delay after which the device may go to
> + sleep if there was no SPI activity (msec).
> +- cs-wake-duration - (optional) Time it takes the device to wake up after
> + toggling CS if it went to sleep (msec).
>
> Some SPI controllers and devices support Dual and Quad SPI transfer mode.
> It allows data in the SPI system to be transferred in 2 wires(DUAL) or 4 wires(QUAD).
> --
> 2.6.6