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. > 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
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