Mark, On Mon, Mar 2, 2015 at 10:47 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Fri, Feb 27, 2015 at 11:41:03AM -0800, Doug Anderson wrote: >> It is possible for _regulator_do_enable() to be called for an >> already-enabled rdev, like in regulator_suspend_finish(). If we were >> using an enable pin (rdev->ena_pin is set) then we'd end up >> incrementing the reference count in regulator_ena_gpio_ctrl() over and >> over again without a decrement. That prevented the GPIO from going to >> the "off" state even after all users were disabled. > >> Fix this by avoiding the call to regulator_ena_gpio_ctrl() when it's >> not needed. > > There's a big jump in this changelog where you assert that we're > avoiding the call "when it's not needed" without explaining the > situations in which this is the case or why. > > Looking at the code it seems that you're adding checks to skip calls in > the standard enable and disable paths but not touching other paths, > based on this patch by itself I can't tell if this is a good idea or > not. It certainly doesn't feel robust - if we're missing reference > counting skipping operations seems likely to lead to other bugs popping > up elsewhere when the other user that isn't doing a disable currently > decides to start doing so. I guess it depends on whether _regulator_do_enable() on an already-enabled rdev is supposed to be a noop or not. My assumption was that it was supposed to be a noop with reference counting handled by _regulator_enable(). My assumption is that regulator drivers themselves shouldn't do reference counting. That is: if you call rdev->desc->ops->enable(rdev) twice you should not have to call rdev->desc->ops->disable(rdev) twice to disable. Right? That means my fix is making the "ena_pin" symmetric to how normal regulator drivers work. The refcounting being skipped by my patch is refcounting that's used only when the same GPIO is shared by more than one regulator. That is, if "vcc_a" uses GPIO1 and "vcc_b" also uses "GPIO1" we need refcounting. GPIO1 will be in the "on" state if either vcc_a or vcc_b is on. The problem came in because _regulator_do_enable() was incrementing the shared refcount every time it was called even if the specific regulator was already on. Anyway, I looked at Javier's patch and it's also fine / reasonable. ...and in fact I would argue that possibly we could take both patches. Javier's patch eliminates the one known place where _regulator_do_enable() is called for an already-enabled regulator and my patch means that if someone else adds a new call we won't end up back in this same subtle bug. I'm happy to update the CL desc to make it more obvious if you'd like. -Doug -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html