From: Daniel Palmer <dan...@0x0f.com> > On Fri, 12 Mar 2021 at 01:11, Mark-PK Tsai <mark-pk.t...@mediatek.com> wrote: > > Why irq could accept either? > > As the irq intc has no way to clear it's triggered state (no eoi) it > must just pass the signal through instead of latching it? > Otherwise it would latch once and never again right? That's what I > really didn't understand. > If it just passes the signal through and maybe inverts it then the GIC > can use edge or level I think.
Yes, but if we accidentally loss a irq and the interrupt is edge triggered which is latch to level by mst-intc, we will miss all the follow irqs because the driver didn't reset the interrupt status. Actually, I'm not sure if it's possible. But even if it's not, I think use level for parent GIC can better match the hardware signal processing. > > > So maybe we don't need to do extra work to check the type for an fiq or irq > > controller? > > I think without the eoi callback for the fiq it would only ever fire > once. I don't think doing the same eoi callback for the irq intc hurts > anything but it wouldn't do anything either from what I can tell. The reason why I don't do the same eoi callback for irq intc is that it's not ont spec. And some of MTK TV SoC use it for certain debug function which may cause unexpected result. > > > And I will update the patch as following: > > I think maybe Marc or someone else that knows better than I do should > comment on what needs to happen. > My input is just that the fiq controller seems to trigger on an edge, > holds it's signal to the GIC high until eoi happens and then only > triggers again on an edge. > I guess it doesn't matter if it's an edge or level if that's how it > works but you'd only get one interrupt out of it per edge even if > configured as a level interrupt. > > The main thing I didn't want was filtering out edge interrupts > entirely as that breaks using edge interrupts with gpios i.e. using > gpiomon. > With the changes to set the polarity it can now detect rising or > falling edge gpio events. :) Thanks for your feedback and I will send patch v4 which includes the change I proposed in this thread.
