On Sat, 9 Nov 2019 at 23:37, Vladimir Oltean <olteanv@xxxxxxxxx> wrote: > > On Sat, 9 Nov 2019 at 23:05, Andrew Lunn <andrew@xxxxxxx> wrote: > > > > On Sat, Nov 09, 2019 at 08:52:54PM +0100, Alexander Stein wrote: > > > On Saturday, November 9, 2019, 4:21:51 PM CET Vladimir Oltean wrote: > > > > On 09/11/2019, Andrew Lunn <andrew@xxxxxxx> wrote: > > > > > On Sat, Nov 09, 2019 at 12:56:42PM +0200, Vladimir Oltean wrote: > > > > >> On the LS1021A-TSN board, the 2 Atheros AR8031 PHYs for eth0 and eth1 > > > > >> have interrupt lines connected to the shared IRQ2_B LS1021A pin. > > > > >> > > > > >> The interrupts are active low, but the GICv2 controller does not support > > > > >> active-low and falling-edge interrupts, so the only mode it can be > > > > >> configured in is rising-edge. > > > > > > > > > > Hi Vladimir > > > > > > > > > > So how does this work? The rising edge would occur after the interrupt > > > > > handler has completed? What triggers the interrupt handler? > > > > > > > > > > Andrew > > > > > > > > > > > > > Hi Andrew, > > > > > > > > I hope I am not terribly confused about this. I thought I am telling > > > > the interrupt controller to raise an IRQ as a result of the > > > > low-to-high transition of the electrical signal. Experimentation sure > > > > seems to agree with me. So the IRQ is generated immediately _after_ > > > > the PHY has left the line in open drain and it got pulled up to Vdd. > > > > > > > > It is correct GIC only supports raising edge and active-high. The > > > IRQ[0:5] on ls1021a are a bit special though. They not directly > > > connected to GIC, but there is an optional inverter, enabled by > > > default. > > > > Ah, O.K. So configuring for a rising edge is actually giving a falling > > edge. Which is why it works. > > > > Actually supporting this correctly is going a cause some pain. I > > wonder how many DT files currently say rising/active high, when in > > fact falling/active low is actually being used? And when the IRQ > > controller really does support active low and falling, things brake? > > > > Vladimir, since this is a shared interrupt, you really should use > > active low here. Maybe the first step is to get control of the > > inverter, and define a DT binding which is not going to break > > backwards compatibility. And then wire up this interrupt. > > > > Andrew > > Oh, ok, this is what you mean, thanks Alexander for the clarification. > This sure escalated quickly and is going to keep me busy for a while. > > -Vladimir Sorry, I'm still a bit in shock, since this hit me in the face from nowhere, so I hadn't followed the entire history when I sent the above email. It looks after all that Kurt and Rasmus have picked this up again and that the latest patch set is from 2 days ago, I'll take a look at that... https://lwn.net/Articles/804103/ Thanks, -Vladimir
