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. Thanks. -- Dmitry -- 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
