[PATCH v3 1/3] power: Add simple poweroff-gpio driver

[andrew@lunn.ch (Andrew Lunn)]

Hi Jason

These are good comments from Stephan that i want to address. However,
i also don't want to delay the pull-requests direction arm-soc, the
merge window is getting close. Both Linus and Anton have Acked the
current version, so please go with what you have and i will produce a
patch over the top. If its available before Arnd pulls, you can squash
it, otherwise send it upstream as a standalone patch.

    Thanks
	Andrew


On Mon, Nov 19, 2012 at 10:38:06AM -0700, Stephen Warren wrote:
> On 11/17/2012 01:51 AM, Andrew Lunn wrote:
> > Given appropriate devicetree bindings, this driver registers a
> > pm_power_off function to set a GPIO line high/low to power down
> > your board.
> 
> > diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> 
> > +menuconfig POWER_RESET
> > +	bool "Board level reset or power off"
> > +	help
> > +	  Provides a number of drivers which either reset a complete board
> > +	  or shut it down, by manipulating the main power supply on the board.
> > +
> > +	  Say Y here to enable board reset and power off
> > +
> > +config POWER_RESET_GPIO
> > +	bool "GPIO power-off driver"
> > +	depends on OF_GPIO && POWER_RESET
> 
> I assume CONFIG_POWER_RESET won't really provide any/much
> infra-structure itself. So, does it make sense to put all the individual
> drives inside "if POWER_RESET" or a menu definition, so they don't all
> have to depend on POWER_RESET explicitly?
> 
> > diff --git a/drivers/power/reset/gpio-poweroff.c b/drivers/power/reset/gpio-poweroff.c
> 
> > +static void gpio_poweroff_do_poweroff(void)
> > +{
> > +	BUG_ON(gpio_num == -1);
> 
> Perhaps use gpio_is_valid() here?
> 
> > +	/* drive it active */
> > +	gpio_direction_output(gpio_num, !gpio_active_low);
> 
> The rest of the code below doesn't make a lot of sense to me. From
> reading the binding documentation, it seems like the GPIO is expected to
> be level-sensitive, and as such the above gpio_direction_output() call
> should be all that's needed. What is the code below doing? If this
> driver supports either a level-sensitive GPIO or generating a pulse on a
> GPIO, I think the binding should be enhanced to specify which signalling
> type is required. Also, all the delays should be specified as DT properties.
> 
> > +	mdelay(100);
> > +	/* rising edge or drive inactive */
> 
> You can't assume that an active->inactive edge is a rising edge if you
> allow the polarity to be configurable; I would remove that part of the
> comment. Same below for "falling edge".
> 
> > +	gpio_set_value(gpio_num, gpio_active_low);
> > +	mdelay(100);
> > +	/* falling edge */
> > +	gpio_set_value(gpio_num, !gpio_active_low);
> > +
> > +	/* give it some time */
> > +	mdelay(3000);
> 
> > +static int __devinit gpio_poweroff_probe(struct platform_device *pdev)
> 
> > +	gpio_num = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
> > +	if (gpio_num < 0) {
> 
> Perhaps use gpio_is_valid() here?
> 
> > +		pr_err("%s: Could not get GPIO configuration: %d",
> > +		       __func__, gpio_num);
> > +		return -ENODEV;
> > +	}
> 
> This doesn't handle deferred probe correctly; if gpio_num ==
> -EPROBE_DEFER, then this function needs to return -EPROBE_DEFER too; why
> not "return gpio_num" rather than "return -ENODEV" above?
> 
> > +	gpio_active_low = flags & OF_GPIO_ACTIVE_LOW;
> > +
> > +	if (of_get_property(pdev->dev.of_node, "input", NULL))
> > +		input = true;
> 
> Perhaps use of_property_read_bool() here.
> 
> > +static int __devexit gpio_poweroff_remove(struct platform_device *pdev)
> > +{
> > +	if (gpio_num != -1)
> > +		gpio_free(gpio_num);
> 
> Perhaps use gpio_is_valid() here? Actually, how could this happen;
> presumably if the GPIO is valid, probe() never succeeded, so you should
> always just free the GPIO.
> 
> > +static struct platform_driver gpio_poweroff_driver = {
> > +	.probe = gpio_poweroff_probe,
> > +	.remove = __devexit_p(gpio_poweroff_remove),
> > +	.driver = {
> > +		   .name = "poweroff-gpio",
> > +		   .owner = THIS_MODULE,
> > +		   .of_match_table = of_gpio_poweroff_match,
> > +		   },
> 
> There seems to be a mix of TAB/space indents there, and the closing }
> should probably be aligned with the start of ".driver"?
> 
> > +MODULE_LICENSE("GPL");
> 
> That should be "GPL v2".
>