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

[Marc Zyngier <maz@kernel.org>]

On 2019-11-12 15:03, Vladimir Oltean wrote:
> On Tue, 12 Nov 2019 at 15:49, Marc Zyngier <maz@kernel.org> wrote:
>>
>> On 2019-11-12 14:53, Vladimir Oltean wrote:
>> > On Tue, 12 Nov 2019 at 15:20, Rasmus Villemoes
>> > <linux@rasmusvillemoes.dk> wrote:
>> >>
>> >> From: Vladimir Oltean <olteanv@gmail.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@gmail.com>
>> >> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.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...