Hi Brian, On 05/08/2018 10:31 AM, JeffyChen wrote: > Hi Brian, > > On 05/08/2018 09:56 AM, Brian Norris wrote: >> On Tue, May 08, 2018 at 09:36:24AM +0800, Jeffy Chen wrote: >>> On 05/08/2018 06:15 AM, Brian Norris wrote: >>>> On the other hand...this also implies there may be a race condition >>>> there, where we might lose an interrupt if there is an edge between the >>>> re-configuration of the polarity in rockchip_irq_demux() and the >>>> clearing/handling of the interrupt (handle_edge_irq() -> >>>> chip->irq_ack()). If we have an edge between there, then we might ack >>>> it, but leave the polarity such that we aren't ready for the next >>>> (inverted) edge. >>> >>> if let me guess, the unexpected irq we saw is the hardware trying to >>> avoid >>> losing irq? for example, we set a EDGE_RISING, and the hardware saw >>> the gpio >>> is already high, then though it might lost an irq, so fake one for safe? >> >> I won't pretend to know what the IC designers were doing, but I don't >> think that would resolve the problem I'm talking about. The sequence is >> something like: >> 1. EDGE_BOTH IRQ occurs (e.g., low to high) >> 2. reconfigure polarity in rockchip_irq_demux() (polarity=low) >> 3. continue to handle_edge_irq() >> 4. another HW edge occurs (e.g., high to low) >> 5. handle_edge_irq() (from 3) acks (clears) IRQ (before a subsequent >> rockchip_irq_demux() gets a chance to run and flip the polarity) >> ... >> >> Now the polarity is still low, but the next trigger should be a >> low-to-high edge. > > oops, i see the problem. > > so what if we do these: > 1/ edge irq triggered > 2/ read gpio level > 3/ handle irq(ack irq) > 4/ toggle edge mode(with a while gpio level check) > > if the gpio changed in 2/ -> 3/, the 4/ will trigger an irq when writing > GPIO_INT_POLARITY(which is what we are trying to avoid in the set_type > case) > > but this would not work if i'm wrong about how the HW fake an irq when > changing POLARITY... > > > or maybe we could just check the gpio status again after > handle_edge_irq, and correct the polarity in this case i saw the pinctrl-msm.c do this in the ack(), and also at the end of set_type(), which might avoid another race in the set_type() > >> >>> i'll try to confirm it with IC guys. >> >> Brian >> >> >> >
