Hi Sebastian,
Thanks for the feedback.
On Tue, Aug 26, 2014 at 6:43 PM, Sebastian Reichel <s...@kernel.org> wrote:
> Hi David,
>
> On Tue, Aug 26, 2014 at 04:45:05PM -0700, David Riley wrote:
>> This driver registers a restart handler to set a GPIO line high/low
>> to reset a board based on devicetree bindings.
>
> Driver looks fine to me. I have some comments about the
> Documentation, though:
>
>> [...]
>> diff --git a/Documentation/devicetree/bindings/gpio/gpio-restart.txt
>> b/Documentation/devicetree/bindings/gpio/gpio-restart.txt
>> new file mode 100644
>> index 0000000..7cd58788
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/gpio/gpio-restart.txt
>> @@ -0,0 +1,48 @@
>> +Driver a GPIO line that can be used to restart the system as a
>> +restart handler.
>
> Please fix the Typo (first word).
Fixed.
>
>> [...]
>> +
>> +The driver supports both level triggered and edge triggered power off.
>> +At driver load time, the driver will request the given gpio line and
>> +install a restart handler.
>
> The wording is too driver centric IMHO. You are supposed to document
> the binding in a generic way. Maybe start with something like:
>
> "This binding supports level and edge triggered reset."
>
> (power off is the wrong word, since there is already gpio-poweroff).
I've cleaned this up for v2.
>> +If the optional properties 'input' is +not found, the GPIO line
>> +will be driven in the inactive state. Otherwise its configured
>> +as an input.
>
> What is this needed for?
This allows other hardware to be attached to the same line to reset
the system. Carried forward from the gpio-poweroff implementation I
based this on.
>> +When do_kernel_restart is called the various restart handlers will be tried
>> +in order. The gpio is configured as an output, and drive active, so
>> +triggering a level triggered power off condition. This will also cause an
>> +inactive->active edge condition, so triggering positive edge triggered
>> +power off. After a delay of 100ms, the GPIO is set to inactive, thus
>> +causing an active->inactive edge, triggering negative edge triggered power
>> +off. After another 100ms delay the GPIO is driver active again. If the
>> +power is still on and the CPU still running after a 3000ms delay, a
>> +WARN_ON(1) is emitted.
>
> I really appreciate the description of the driver (it made it easier
> to review it :)), but Documentation/devicetree should avoid
> Linuxisms. In other words: this is the wrong location for the
> description.
I've cleaned this up as well and made the explicit delays configurable.
>
>> +Required properties:
>> +- compatible : should be "gpio-restart".
>> +- gpios : The GPIO to set high/low, see "gpios property" in
>> + Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be
>> + low to power down the board set it to "Active Low", otherwise set
>> + gpio to "Active High".
>> +
>> +Optional properties:
>> +- input : Initially configure the GPIO line as an input. Only reconfigure
>> + it to an output when the machine_restart function is called. If this
>> optional
>> + property is not specified, the GPIO is initialized as an output in its
>> + inactive state.
>> +- priority : A priority ranging from 0 to 255 (default 128) according to
>> + the following guidelines:
>> + 0: Restart handler of last resort, with limited restart
>> + capabilities
>> + 128: Default restart handler; use if no other restart handler is
>> + expected to be available, and/or if restart functionality is
>> + sufficient to restart the entire system
>> + 255: Highest priority restart handler, will preempt all other
>> + restart handlers
>
> You should add a short information about the property type here
> (e.g. "8 bit integer" for priority).
As per Olof's comments I've just changed this to be a regular cell for
consistency with other bindings and will handle the range checking
internally.
>
>> +Examples:
>> +
>> +gpio-restart {
>> + compatible = "gpio-restart";
>> + gpios = <&gpio 4 0>;
>> + priority = /bits/ 8 <200>;
>> +};
>> [...]
>
> -- Sebastian
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