On Mon, Feb 27, 2017 at 7:02 PM, Stefan Wahren <stefan.wahren@xxxxxxxx> wrote: > on BCM2835 (Raspberry Pi) the firmware on the VideoCore and Linux on the ARM core share > a common pin "space". Depending on the board revision the VideoCore needs to controls > some pins, which shouldn't be claimed by Linux on the ARM. > > What is the right way to exclude control on Linux for those pins in order to avoid possible > harmful operations? Do you want to do this statically (at boot) or dynamically (at runtime)? If you want to do it statically, at boot time: Just add some NOOP function (i.e. a function that result in zero register writes or anything) named "videocore-reserved" or something to the driver in drivers/pinctrl/bcm/pinctrl-bcm2835.c, make it applicable to the affected pins, making it possible to create a state that will combine the function "videocore-reserved" with these pins, resulting in them being exclusively used for that. Then in the videocore device tree node (I assume there is something like such) create a pinctrl state that just take all these pins with this dummy function. (If the videocore does not even have a device tree node, hog all those pins to that function using hogs as described in Documentaion/pinctrl.txt, essentially just take the pins for the pin controller itself.) If you want to do it at runtime, you need some communication link to the videocore (I guess) and then it is essentially the same approach but done using proper states reflecting whether the videocore is actively using them or not, but for the simple case even this would be easiest done using the static approach above. You may need a dynamic solution if you want to remux the pins to ground when going to sleep for example, then something must move the pins from "default" to "sleep" state and back, and that needs to be the videocore driver in the kernel I guess. Yours, Linus Walleij -- 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
