Lars Poeschel <larsi@xxxxxxxxxxxxxxxxx> writes: > From: Linus Walleij <linus.walleij@xxxxxxxxxx> > > Currently the kernel is ambigously treating GPIOs and interrupts > from a GPIO controller: GPIOs and interrupts are treated as > orthogonal. This unfortunately makes it unclear how to actually > retrieve and request a GPIO line or interrupt from a GPIO > controller in the device tree probe path. > > In the non-DT probe path it is clear that the GPIO number has to > be passed to the consuming device, and if it is to be used as > an interrupt, the consumer shall performa a gpio_to_irq() mapping > and request the resulting IRQ number. > > In the DT boot path consumers may have been given one or more > interrupts from the interrupt-controller side of the GPIO chip > in an abstract way, such that the driver is not aware of the > fact that a GPIO chip is backing this interrupt, and the GPIO > side of the same line is never requested with gpio_request(). > A typical case for this is ethernet chips which just take some > interrupt line which may be a "hard" interrupt line (such as an > external interrupt line from an SoC) or a cascaded interrupt > connected to a GPIO line. > > This has the following undesired effects: > > - The GPIOlib subsystem is not aware that the line is in use > and willingly lets some other consumer perform gpio_request() > on it, leading to a complex resource conflict if it occurs. And another reason, which happens on OMAP (not that the others aren't already enough to make the case): - Platform-specific power management code may gate clocks or power to unused GPIO banks resulting in faults when accessing a GPIO that has not been properly requested via gpio_request(). > - The GPIO debugfs file claims this GPIO line is "free". > > - The line direction of the interrupt GPIO line is not > explicitly set as input, even though it is obvious that such > a line need to be set up in this way, often making the system > depend on boot-on defaults for this kind of settings. Kevin -- 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
