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authorDouglas Anderson <dianders@chromium.org>2020-12-11 14:15:35 -0800
committerMarc Zyngier <maz@kernel.org>2020-12-12 10:46:02 +0000
commit2f5fbc4305d07725bfebaedb09e57271315691ef (patch)
tree270907bb47379127281197dd2841e7450dd5621a /kernel/irq/Kconfig
parente15f2fa959f2cce8a05e8e3a596e75d068cd42c5 (diff)
downloadlinux-stericsson-2f5fbc4305d07725bfebaedb09e57271315691ef.tar.gz
irqchip/qcom-pdc: Fix phantom irq when changing between rising/falling
We have a problem if we use gpio-keys and configure wakeups such that we only want one edge to wake us up. AKA: wakeup-event-action = <EV_ACT_DEASSERTED>; wakeup-source; Specifically we end up with a phantom interrupt that blocks suspend if the line was already high and we want wakeups on rising edges (AKA we want the GPIO to go low and then high again before we wake up). The opposite is also problematic. Specifically, here's what's happening today: 1. Normally, gpio-keys configures to look for both edges. Due to the current workaround introduced in commit c3c0c2e18d94 ("pinctrl: qcom: Handle broken/missing PDC dual edge IRQs on sc7180"), if the line was high we'd configure for falling edges. 2. At suspend time, we change to look for rising edges. 3. After qcom_pdc_gic_set_type() runs, we get a phantom interrupt. We can solve this by just clearing the phantom interrupt. NOTE: it is possible that this could cause problems for a client with very specific needs, but there's not much we can do with this hardware. As an example, let's say the interrupt signal is currently high and the client is looking for falling edges. The client now changes to look for rising edges. The client could possibly expect that if the line has a short pulse low (and back high) that it would always be detected. Specifically no matter when the pulse happened, it should either have tripped the (old) falling edge trigger or the (new) rising edge trigger. We will simply not trip it. We could narrow down the race a bit by polling our parent before changing types, but no matter what we do there will still be a period of time where we can't tell the difference between a real transition (or more than one transition) and the phantom. Fixes: f55c73aef890 ("irqchip/pdc: Add PDC interrupt controller for QCOM SoCs") Signed-off-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Marc Zyngier <maz@kernel.org> Tested-by: Maulik Shah <mkshah@codeaurora.org> Reviewed-by: Maulik Shah <mkshah@codeaurora.org> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Link: https://lore.kernel.org/r/20201211141514.v4.1.I2702919afc253e2a451bebc3b701b462b2d22344@changeid
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