On Wednesday, April 25, 2018 8:14:35 PM CEST Dmitry Torokhov wrote: > On Wed, Apr 25, 2018 at 10:00:31AM -0500, Rob Herring wrote: > > On Tue, Apr 24, 2018 at 5:58 PM, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > > > Hi Linus, Rafael, all > > > > > > Our GPIO controller driver: gpio-brcmstb.c has a shutdown callback which > > > gets invoked when the system is brought into poweroff aka S5. So far so > > > good, except that we also wish to use gpio_keys.c as a possible wake-up > > > source, so we may have a number of GPIO pins declared as gpio-keys that > > > allow the system to wake-up from deep slumber. > > > > > > Recently we noticed that we could easily get into a state where > > > gpio-brcmstb.c::brcmstb_gpio_shutdown() gets called first, and then > > > gpio_keys.c::gpio_keys_suspend() gets called later, which is too late to > > > have the enable_irq_wake() call do anything sensible since we have > > > suspend its parent interrupt controller before. This is completely > > > expected unfortunately because these two drivers are both platform > > > device instances with no connection to one another except via Device > > > Tree and the use of the GPIOLIB APIs. > > > > > > First solution is to make sure that gpio-keys nodes are declared in > > > Device Tree *before* the GPIO controller. This works because Device Tree > > > nodes are probed in the order in which they are declared in Device Tree > > > and that directly influences the order in which platform devices are > > > created. Problem with that is that this is easy to miss and it may not > > > work with overlays, kexec reconstructing DT etc. etc. > > > > I'm going to make of_platform_populate randomize the order it creates devices... > > > > > Another possible solution would be have the GPIO controller nodes have > > > the GPIO consumers nodes such as gpio-keys, gpio-leds etc., and that > > > would allow the Linux device driver model to create an appropriate > > > child/parent relationship. This would unfortunately require Device Tree > > > changes everywhere to make that consistent, and it would be a special > > > case, because not all GPIO consumers are eligible as child nodes of > > > their parent GPIO controller, there are plenty of other consumers that > > > are not suitable for being moved under a parent GPIO controller node. > > > This would also mean that we need to "probe" GPIO controller nodes to > > > populate their child nodes (e.g: of_platform_bus_populate). > > > > > > I am thinking a more generic solution might involve some more complex > > > tracking of the provider <-> consumer, but there is room for breakage. > > > > That's what device connections are for. It probably just needs the > > GPIO core to create the links. (but I've not looked into it at all). > > Not all APIs accept device as parameter to easily create links. But I > wonder, for cases like this, if we could not simply move the device to > the end of the dpm list after successful binding it to a driver. The > assumption that when GOPIs or other resources are not ready they'll > return -EPROBE_DEFER and probing would fail. Not just to the end of dpm_list if shutdown is involved. Also if you need runtime PM to follow the dependencies, this isn't sufficient. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
