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

[Doug Anderson]

Hi,

On Thu, Jun 30, 2016 at 12:12 AM, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
> CC devicetree

And Rob and Mark...

 ./scripts/get_maintainer.pl -f
Documentation/devicetree/bindings/spi/spi-bus.txt

Mark Brown <broonie@xxxxxxxxxx> (maintainer:SPI SUBSYSTEM)
Rob Herring <robh+dt@xxxxxxxxxx> (maintainer:OPEN FIRMWARE AND
FLATTENED DEVICE TREE BINDINGS)
Mark Rutland <mark.rutland@xxxxxxx> (maintainer:OPEN FIRMWARE AND
FLATTENED DEVICE TREE BINDINGS)
linux-spi@xxxxxxxxxxxxxxx (open list:SPI SUBSYSTEM)
devicetree@xxxxxxxxxxxxxxx (open list:OPEN FIRMWARE AND FLATTENED
DEVICE TREE BINDINGS)
linux-kernel@xxxxxxxxxxxxxxx (open list)


> 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(+)

Overall note is that devicetree bindings patches should be _before_
the code that uses them, so you should swap patch #1 and patch #2.

>>
>> 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.

You probably also need a property for how long it needs to be asserted
when you "toggle" 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).

I believe that from your code the second two properties are both
required if the first property is set.  That should be in the
bindings.