On Thu, 02 Aug 2018 07:51:04 +0100, Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote: > > On Thu, Aug 02 2018 at 00:08 -0600, Marc Zyngier wrote: > > Hi Lina, > > > > On Wed, 01 Aug 2018 20:45:38 +0100, > > Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote: > >> > >> Thanks for the feedback, Marc. > >> > >> On Wed, Aug 01 2018 at 00:31 -0600, Marc Zyngier wrote: > >> > On Wed, 01 Aug 2018 03:00:18 +0100, > >> > Lina Iyer <ilina@xxxxxxxxxxxxxx> wrote: > >> >> > >> >> +static irqreturn_t wake_irq_gpio_handler(int irq, void *data) > >> >> +{ > >> >> + struct irq_data *irqd = data; > >> >> + struct irq_desc *desc = irq_data_to_desc(irqd); > >> >> + struct irq_chip *chip = irq_desc_get_chip(desc); > >> >> + struct gpio_chip *gc = irq_data_get_irq_chip_data(irqd); > >> >> + int irq_pin = irq_find_mapping(gc->irq.domain, irqd->hwirq); > >> >> + > >> >> + chained_irq_enter(chip, desc); > >> >> + generic_handle_irq(irq_pin); > >> >> + chained_irq_exit(chip, desc); > >> > > >> > That's crazy. I'm not even commenting on the irq handler vs chained > >> > irqchip thing, but directly calling into a completely different part > >> > of the irq hierarchy makes me feel nauseous, > >> > > >> I know the sentiment; I am not too happy about it myself. Explanation > >> below. > >> > >> > Why isn't the interrupt still pending at the pinctrl level? Looking at > >> > the diagram in the cover letter, I'd have hoped that the signal routed > >> > to the PDC would wakeup the GIC, but that by virtue of being *also* > >> > wired to the TLMM, the interrupt would be handled via the normal path. > >> > > >> The short answer: TLMM is not active to sense a wakeup interrupt. > > > > I get that bit. See below for the bit I don't get. > > > >> When we enter system sleep mode, the TLMM and the GIC are powered off > >> and the PDC is the only powered-on interrupt controller. The IRQs > >> configured at the PDC are the only ones capable of waking the system. > >> Upon sensing the interrupt, the PDC intiates a system wakeup and replays > >> the interrupt to the GIC. The GIC relays that to AP. Unfortunately, the > >> interrupts from the GPIO do not trigger the TLMM summary line. Therefore > >> this handler needs to figure out what GPIO caused the wakeup and notify > >> the corresponding driver. > > > > That's most bizarre. What causes the TLMM output line not to reflect > > the fact that an input is asserted? > There is a parallel line that is directed from the PIN directly to the > PDC in addition to the TLMM. This line does not go through the TLMM. I got that from the cover letter. > > Active path _____ > /-------------- > [ TLMM ] --------> | | > [ Device GPIO ] summary | GIC | ==> > \ | | > ----------------> [ PDC ] ---------> |_____| > Wakeup path GPIO as IRQ IRQ > > > I understand that it has been > > turned off, but surely the PDC wakes it up at the same time as the > > GIC, and it should realise that there is something pending... > > > PDC is always-on and when it detects any interrupt, will wakeup the GIC > and then replay the interrupt line to the GIC. This interrupt line is > not the summary line, but a separate line from GPIO/PIN to the PDC. > > Since the TLMM was also in low power mode, when the GIC was powered > down, the TLMM never sees the IRQ and therefore will not send the > summary line to GIC. The wakeup path is GPIO -> PDC -> GIC. Sure. But once woken up (GIC *and* TLMM), the gpio line (which I assume is level) is still high at the TLMM input. So why isn't it registering that state once it has been woken up? I can understand that it would be missing an edge. But that doesn't hold for level signalling. > > >> > Why isn't that the case? And if that's because the HW is broken and > >> > doesn't buffer edge interrupts, why can't you use the resend mechanism > >> > instead? > >> > > >> The PDC hardware can replay the interrupts accurately. However, it will > >> replay only the pin and its not the TLMM summary IRQ. The handler here, > >> needs to notify the driver that the wakeup interrupt happened and needs > >> to take action. If I could trip the summary IRQ in this handler that > >> would work too. Can it be done? > > > > So the TLMM has indeed noticed the interrupt and you can read the TLMM > > status registers to find out what fired? > I think that's where it is probably confusing. The TLMM will not see the > interrupt because it was in low power mode. See above. I can buy that for edge, but not level. Thanks, M. -- Jazz is not dead, it just smell funny. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html