On Tuesday 19 of November 2013 10:59:39 Doug Anderson wrote: > On Tue, Nov 19, 2013 at 10:46 AM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > > On 11/19/2013 10:15 AM, Tomasz Figa wrote: > >> This patch extends the range of settings configurable via pinfunc API > >> to cover pin value as well. This allows configuration of default values > >> of pins. > > > > Shouldn't there be a driver that acquires the GPIO that's output to the > > pin, and configures the output value? IIRC there have been previous > > discussions re: having a list of e.g. initial GPIO output values in DT, > > and that was rejected, and this patch seems to be doing almost the exact > > same thing, just at the pinctrl level rather than GPIO level. > > > > That all said, I admit this could be a useful feature... > > I haven't followed all of the previous discussions, but I know I've > run into scenarios where something like this would be useful. The one > that comes to mind is: > > * We've got GPIOs that default at bootup to a pulled up input since > the default state of the pin should be "high". > > * These pins are really intended to be outputs, like an "enable", > "reset", or "power down" line for a peripheral. The pullup is strong > enough to give us a good default state but we really want outputs. > > * We'd like to provide this GPIO to a peripheral through device tree. > ...and we'd like all the pinmux to be setup automatically so we use > pinctrl-names = "default". > > * If we set the pinmux up as "output" then there's a chance that the > line will glitch at bootup since the pinmux happens (changing the pin > to output) before the driver has a chance to run. > > > Does that sound like the same scenario you're trying to solve Tomasz? Yes. That's one of the use cases I had in my mind. Best regards, Tomasz -- 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
