linux-kernel - Re: [PATCH 2/2] ARM: dts: ls1021a-tsn: Use interrupts for the SGMII PHYs

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Message-ID: <CA+h21hqxpy-n6HBkyGSKFEm_CujG5x3Y3Wj-frj0OSwbVWgCng@mail.gmail.com>
Date:   Tue, 12 Nov 2019 16:12:02 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH 2/2] ARM: dts: ls1021a-tsn: Use interrupts for the SGMII PHYs

On Tue, 12 Nov 2019 at 16:04, Marc Zyngier <maz@...nel.org> wrote:
>
> On 2019-11-12 15:03, Vladimir Oltean wrote:
> > On Tue, 12 Nov 2019 at 15:49, Marc Zyngier <maz@...nel.org> wrote:
> >>
> >> On 2019-11-12 14:53, Vladimir Oltean wrote:
> >> > On Tue, 12 Nov 2019 at 15:20, Rasmus Villemoes
> >> > <linux@...musvillemoes.dk> wrote:
> >> >>
> >> >> From: Vladimir Oltean <olteanv@...il.com>
> >> >>
> >> >> 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.
> >> >>
> >> >> Switching to interrupts offloads the PHY library from the task of
> >> >> polling the MDIO status and AN registers (1, 4, 5) every second.
> >> >>
> >> >> Unfortunately, the BCM5464R quad PHY connected to the switch does
> >> >> not
> >> >> appear to have an interrupt line routed to the SoC.
> >> >>
> >> >> Signed-off-by: Vladimir Oltean <olteanv@...il.com>
> >> >> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> >> >> ---
> >> >>  arch/arm/boot/dts/ls1021a-tsn.dts | 4 ++++
> >> >>  1 file changed, 4 insertions(+)
> >> >>
> >> >> diff --git a/arch/arm/boot/dts/ls1021a-tsn.dts
> >> >> b/arch/arm/boot/dts/ls1021a-tsn.dts
> >> >> index 5b7689094b70..135d36461af4 100644
> >> >> --- a/arch/arm/boot/dts/ls1021a-tsn.dts
> >> >> +++ b/arch/arm/boot/dts/ls1021a-tsn.dts
> >> >> @@ -203,11 +203,15 @@
> >> >>         /* AR8031 */
> >> >>         sgmii_phy1: ethernet-phy@1 {
> >> >>                 reg = <0x1>;
> >> >> +               /* SGMII1_PHY_INT_B: connected to IRQ2, active
> >> low
> >> >> */
> >> >> +               interrupts-extended = <&extirq 2
> >> >> IRQ_TYPE_EDGE_FALLING>;
> >> >>         };
> >> >>
> >> >>         /* AR8031 */
> >> >>         sgmii_phy2: ethernet-phy@2 {
> >> >>                 reg = <0x2>;
> >> >> +               /* SGMII2_PHY_INT_B: connected to IRQ2, active
> >> low
> >> >> */
> >> >> +               interrupts-extended = <&extirq 2
> >> >> IRQ_TYPE_EDGE_FALLING>;
> >> >>         };
> >> >>
> >> >>         /* BCM5464 quad PHY */
> >> >> --
> >> >> 2.23.0
> >> >>
> >> >
> >> > +netdev and Andrew for this patch, since the interrupt polarity
> >> > caught
> >> > his attention in v1.
> >>
> >> Certainly, the comments and the interrupt specifier do not match.
> >> Which one is true?
> >>
> >>          M.
> >> --
> >> Jazz is not dead. It just smells funny...
> >
> > The interrupt specifier certainly works. So that points to an issue
> > with the description. What do you mean, exactly? Does "active low"
> > mean "level-triggered"? How would you have described this?
>
> Active Low definitely implies level triggered. And if that's how it
> is described in the TRM, than the interrupt specifier is wrong, and
> just *seem to work* because the level goes back to high between two
> interrupts.
>
> Also, shared *edge* interrupts do not work, full stop. So I'm pretty
> convinced that what you have here is just wrong.
>
>          M.
> --
> Jazz is not dead. It just smells funny...

Ok, I've tested both interrupts with IRQ_TYPE_LEVEL_LOW and they still
work. I'll let Rasmus re-send if there is no trouble with the dtsi
patch. Sorry for the trouble and thanks for teaching me something new.

Cheers,
-Vladimir