Felipe, On Sun, Feb 5, 2012 at 14:38, Felipe Balbi <balbi@xxxxxx> wrote: > Hi, > > On Sun, Feb 05, 2012 at 12:37:55PM +0530, Varadarajan, Charulatha wrote: >> Felipe, >> >> On Sat, Feb 4, 2012 at 21:38, Felipe Balbi <balbi@xxxxxx> wrote: >> > >> > Hi, >> > >> > On Fri, Feb 03, 2012 at 09:50:19AM -0800, Kevin Hilman wrote: >> > > Felipe Balbi <balbi@xxxxxx> writes: >> > > >> > > [...] >> > > >> > > >> >This question remains. Why do we need those funtions ? >> > > >> >> > > >> These functions are called from the CPUIdle path so outside the scope >> > > >> of the GPIO driver. These are part of a bunch of nasty PM hacks we >> > > >> are doing in the CPU idle loop. We are in the process of getting rid >> > > >> of most of them, but it looks like some are still needed. >> > > > >> > > > Too bad. I can see that the gpio pm implementation seems a bit >> > > > "peculiar". I mean, pm does reference counting and yet the driver has >> > > > checks to prevent multiple gets and puts on a single bank (meaning that >> > > > pm counter will be either 0 or 1 at any point in time). >> > > > >> > > > To me it looks like those functions are there in order to forcefully put >> > > > PER power domain in OFF because drivers are always holding a reference >> > > > to their gpios (drivers generally gpio_request() on probe() and >> > > > gpio_free() on remove()). >> > > > >> > > > Looks like the entire pm implementation on OMAP gpio driver has always >> > > > considered only the fact that gpios can be requested and freed, but >> > > > never that we want the system to go to OFF even while gpios are >> > > > requested, because we have I/O PAD wakeups. At some point that has to be >> > > > sorted out because that HACK is quite ugly :-) >> > > > >> > > > I'll see if I find some time to go over the interactions between >> > > > gpio-omap.c and pm24x.c and pm34xx.c any of these days, but I can't >> > > > promise anything ;-) >> > > >> > > If you look at the state of these prepare/resume hacks at the end of >> > > this series, you'll see that they are significantly cleaner and do >> > > nothing but call the runtime PM hooks. >> > >> > sure, definitely. >> > >> > > We have explored several ways to get rid of them completely in the idle >> > > path but have not yet come up with a clean way, but this series gets us >> > > a long ways towards that goal. >> > >> > have you thought about being a bit more aggressive at when to >> > runtime_get and runtime_put ? >> > >> > I didn't test below (will do probably on monday), but I think this will >> > help keeping GPIO block always suspended, and only wake it up when truly >> > needed. That way, you could, at some point, remove that list_head >> > because by the time you reach CPUIdle path, GPIO module is already >> > suspended. That's the theory at least, gotta run it first on silicon to >> > be sure >> > >> > diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c >> > index 4273401..2dd9ced 100644 >> > --- a/drivers/gpio/gpio-omap.c >> > +++ b/drivers/gpio/gpio-omap.c >> > @@ -537,12 +537,7 @@ static int omap_gpio_request(struct gpio_chip *chip, unsigned offset) >> > struct gpio_bank *bank = container_of(chip, struct gpio_bank, chip); >> > unsigned long flags; >> > >> > - /* >> > - * If this is the first gpio_request for the bank, >> > - * enable the bank module. >> > - */ >> > - if (!bank->mod_usage) >> > - pm_runtime_get_sync(bank->dev); >> > + pm_runtime_get_sync(bank->dev); >> >> bank->mod_usage check is used to take care of doing pm_runtime_get*/put* only >> if all the GPIOs in a particular bank are enabled or disabled respectively. > > and why should you care about that ? The first get will enable the > resources you need, the second get will just increase a counter and so > on. So if you have 32 gets, you will disable the module when you have 32 > puts. Agreed! -V Charulatha > >> With the above change, pm_runtime_put*/get* would be called for every >> gpio_request() >> /_free() (that is, for upto 32 pins in OMAP3/4) in a bank irrespective >> of whether other > > so ? > >> GPIO pins are enabled or disabled in the same bank. Hence it is >> required to have a >> check based on mod_usage. > > unnecessary. > > -- > balbi -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
