[PATCH 1/2] gpio-vbus: support disabling D+ pullup on suspend

[balbi@ti.com (Felipe Balbi)]

Hi,

On Wed, Jun 22, 2011 at 05:52:18PM +0400, Dmitry Eremin-Solenikov wrote:
> On 6/22/11, Felipe Balbi <balbi@ti.com> wrote:
> > Hi,
> >
> > On Wed, Jun 22, 2011 at 04:20:16PM +0400, Dmitry Eremin-Solenikov wrote:
> >> Some platforms would like to disable D+ pullup on suspend, to drain as
> >> low power, as possible. E.g. this was requested by mioa701 board
> >> maintainers.
> >
> > I think this makes sense to many platforms, but by doing so, you would
> > loose connection to the Host PC, so you need to make sure your device
> > isn't been used before you go down this road.
> 
> I've thought about this. Should UDC driver should somehow call into OTG
> layer on suspend? My understanding is that otg_set_suspend isn't the call
> that should be done here, is it true?
> 
> My idea was that board can ask for D+ disabling, knowing itself the behaviour
> of the platform driver on suspend (e.g. PXA27x does disable UDC on suspend,
> but I dunno what effect this will cause on Host PC).

Host PC will only see the device disconnecting. So, what happens if the
user has mounted file systems when you decide to go into suspend ?

> 
> >> Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> >> ---
> >>  drivers/usb/otg/gpio_vbus.c   |   32 ++++++++++++++++++++++++++++++++
> >>  include/linux/usb/gpio_vbus.h |    1 +
> >>  2 files changed, 33 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/usb/otg/gpio_vbus.c b/drivers/usb/otg/gpio_vbus.c
> >> index 52733d9..44527bd 100644
> >> --- a/drivers/usb/otg/gpio_vbus.c
> >> +++ b/drivers/usb/otg/gpio_vbus.c
> >> @@ -327,6 +327,34 @@ static int __exit gpio_vbus_remove(struct
> >> platform_device *pdev)
> >>  	return 0;
> >>  }
> >>
> >> +#ifdef CONFIG_PM
> >> +static int gpio_vbus_suspend(struct platform_device *pdev, pm_message_t
> >> state)
> >> +{
> >> +	struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
> >> +	struct gpio_vbus_mach_info *pdata = gpio_vbus->dev->platform_data;
> >> +
> >> +	if (gpio_vbus->otg.gadget && pdata->disconnect_on_suspend) {
> >> +		/* optionally disable D+ pullup */
> >> +		if (gpio_is_valid(pdata->gpio_pullup))
> >> +			gpio_set_value(pdata->gpio_pullup,
> >> +					pdata->gpio_pullup_inverted);
> >> +
> >> +		set_vbus_draw(gpio_vbus, 0);
> >> +	}
> >> +	return 0;
> >> +}
> >> +
> >> +static int gpio_vbus_resume(struct platform_device *pdev)
> >> +{
> >> +	struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
> >> +
> >> +	if (gpio_vbus->otg.gadget)
> >> +		schedule_work(&gpio_vbus->work);
> >> +
> >> +	return 0;
> >> +}
> >
> > actually, the correct way would be to use dev_pm_ops.
> 
> Could I use SIMPLE_DEV_PM_OPS here?

for sure ;-)

> >> +#endif
> >> +
> >>  /* NOTE:  the gpio-vbus device may *NOT* be hotplugged */
> >>
> >>  MODULE_ALIAS("platform:gpio-vbus");
> >> @@ -337,6 +365,10 @@ static struct platform_driver gpio_vbus_driver = {
> >>  		.owner = THIS_MODULE,
> >>  	},
> >>  	.remove  = __exit_p(gpio_vbus_remove),
> >> +#ifdef CONFIG_PM
> >> +	.suspend	= gpio_vbus_suspend,
> >> +	.resume		= gpio_vbus_resume
> >> +#endif
> >
> > also, avoid the ifdef on the driver structure.
> 
> Ack. Was just C&P from gpio-vbus, but it's not an excuse
> to follow bad style.

see what e.g the musb driver does to avoid the ifdef
(drivers/usb/musb/musb_core.c)

-- 
balbi
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