Messages in this thread | | | Date | Wed, 27 Aug 2014 10:56:20 -0700 | Subject | Re: [PATCH v1 1/1] power: Add simple gpio-restart driver | From | David Riley <> |
| |
Hi Sebastian,
Thanks for the feedback.
On Tue, Aug 26, 2014 at 6:43 PM, Sebastian Reichel <sre@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
| |