On 09/10/2013 09:00 AM, Joel Fernandes wrote: > On 07/31/2013 03:35 AM, Javier Martinez Canillas wrote: >> On 07/31/2013 01:44 AM, Linus Walleij wrote: >>> On Tue, Jul 30, 2013 at 6:30 AM, Grant Likely <grant.likely@xxxxxxxxxx> wrote: >>>> On Mon, Jul 29, 2013 at 6:36 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: >>>>> To solve this dilemma, perform an interrupt consistency check >>>>> when adding a GPIO chip: if the chip is both gpio-controller and >>>>> interrupt-controller, walk all children of the device tree, >>>>> check if these in turn reference the interrupt-controller, and >>>>> if they do, loop over the interrupts used by that child and >>>>> perform gpio_reques() and gpio_direction_input() on these, >>>>> making them unreachable from the GPIO side. >>>> >>>> Ugh, that's pretty awful, and it doesn't actually solve the root >>>> problem of the GPIO and IRQ subsystems not cooperating. It's also a >>>> very DT-centric solution even though we're going to see the exact same >>>> issue on ACPI machines. >>> >>> The problem is that the patches for OMAP that I applied >>> and now have had to revert solves it in an even uglier way, >>> leading to breaking boards, as was noticed. >>> >>> The approach in this patch has the potential to actually >>> work without regressing a bunch of boards... >>> >>> Whether this is a problem in ACPI or not remains to be seen, >>> but I'm not sure about that. Device trees allows for a GPIO line >>> to be used as an interrupt source and GPIO line orthogonally, >>> and that is the root of this problem. Does ACPI have the same >>> problem, or does it impose natural restrictions on such use >>> cases? >>> >> >> I agree with Linus here. The problem is that GPIO controllers that can work as >> IRQ sources are treated in the kernel as if there where two separate controlers >> that are rather orthogonal: an irq_chip and a gpio_chip. >> But DT allows to use a GPIO line as an IRQ just by using an omap-gpio phandle as >> "interrupt-parent". >> >> So, there should be a place where both irq_chip and gpio_chip has to be related >> somehow to properly configure a GPIO (request it and setting it as input) when >> used as an IRQ by DT. >> >> My patch for OMAP used an irq_domain_ops .map function handler to configure the >> GPIO when a IRQ was mapped since that seemed to me as the best place to do it. >> This worked well in OMAP2+ platforms but unfortunately broke OMAP1 platforms >> since they are still using legacy domain mapping thus not call .map. > > Just wondering- why .map not called for omap1? irq_create_mapping does seem to > call -> irq_domain_associate which calls map function. For omap case, GPIO > driver does call irq_create_mapping, just like omap2+ no? > That is what I understood too when writing the patch but I remember someone mentioning legacy domain mapping not calling the .map function handler as a possible cause for the OMAP1 regression and since Linus decided to revert the patches in favor of a more general solution I didn't care to check if that was true or not. Now looking at irq_create_mapping() I see that my assumption was correct so I don't know what was the bug that caused the OMAP1 regression. > Further, if for any reason the .map is not called. Can you not call gpio_request > yourself direct in omap_gpio_chip_init function? > No, since you can't request a GPIO for all GPIO pins in the bank. Users have to do it explicitly (or implicitly in the case of GPIO mapped as IRQ in DT). > Does it really matter if you call gpio_request from .map or from the chip_init > function? > Yes it does, because in DT the core calls irq_create_of_mapping() -> irq_create_mapping() -> .map(). That way only are requested the GPIO pins that are mapped as IRQ and not all of them. > Also on a different note.. this would call gpio_request for *every* gpio line, > but isn't that what your original patch that got reverted was doing in > omap_gpio_chip_init: > > + if (!bank->chip.of_node) > + for (j = 0; j < bank->width; j++) > + irq_create_mapping(bank->domain, j); > No it won't. This is only needed for the legacy (non-DT) boot since no one calls irq_create_mapping() so it has to be called explicitly. And in that case .map will be called but gpio_request() won't since the call is made only when bank->chip.of_node is not NULL. > Just trying to understand your initial patch better. > > Regards, > > -Joel > Best regards, Javier -- 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
