RE: [PATCH net-next 1/3] dt-bindings: net: fsl, fec: add "fsl, wakeup-irq" property

[Joakim Zhang <qiangqing.zhang@nxp.com>]

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: 2021年8月14日 2:23
> To: Joakim Zhang <qiangqing.zhang@nxp.com>
> Cc: Andrew Lunn <andrew@lunn.ch>; Florian Fainelli <f.fainelli@gmail.com>;
> davem@davemloft.net; kuba@kernel.org; shawnguo@kernel.org;
> s.hauer@pengutronix.de; festevam@gmail.com; kernel@pengutronix.de;
> dl-linux-imx <linux-imx@nxp.com>; netdev@vger.kernel.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org
> Subject: Re: [PATCH net-next 1/3] dt-bindings: net: fsl, fec: add "fsl,
> wakeup-irq" property
> 
> On Wed, Aug 11, 2021 at 07:57:46AM +0000, Joakim Zhang wrote:
> >
> > Hi Andrew,
> >
> > > -----Original Message-----
> > > From: Andrew Lunn <andrew@lunn.ch>
> > > Sent: 2021年8月10日 22:33
> > > To: Joakim Zhang <qiangqing.zhang@nxp.com>
> > > Cc: Florian Fainelli <f.fainelli@gmail.com>; davem@davemloft.net;
> > > kuba@kernel.org; robh+dt@kernel.org; shawnguo@kernel.org;
> > > s.hauer@pengutronix.de; festevam@gmail.com; kernel@pengutronix.de;
> > > dl-linux-imx <linux-imx@nxp.com>; netdev@vger.kernel.org;
> > > devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> > > linux-arm-kernel@lists.infradead.org
> > > Subject: Re: [PATCH net-next 1/3] dt-bindings: net: fsl, fec: add
> > > "fsl, wakeup-irq" property
> > >
> > > > > > 1) FEC controller has up to 4 interrupt lines and all of these
> > > > > > are routed to GIC
> > > > > interrupt controller.
> > > > > > 2) FEC has a wakeup interrupt signal and always are mixed with
> > > > > > other
> > > > > interrupt signals, and then output to one interrupt line.
> > > > > > 3) For legacy SoCs, wakeup interrupt are mixed to int0 line,
> > > > > > but for i.MX8M
> > > > > serials, are mixed to int2 line.
> > >
> > > So you need to know which of the interrupts listed is the wake up interrupt.
> 
> We already have a way to do this by using 'wakeup' for the interrupt-names
> entry. But I guess that ship has sailed here and that wouldn't work well if not
> just a wakeup source (though you could repeat an interrupt line that's the
> wakeup source).

Yes, I am not sure whether it's a common solution, such as:
interrupts = <GIC_SPI 118 IRQ_TYPE_LEVEL_HIGH>,
		<GIC_SPI 119 IRQ_TYPE_LEVEL_HIGH>,
		<GIC_SPI 120 IRQ_TYPE_LEVEL_HIGH>,
		<GIC_SPI 121 IRQ_TYPE_LEVEL_HIGH>,
		<GIC_SPI 120 IRQ_TYPE_LEVEL_HIGH>,
interrupt-names = "int0", "int1", "int2", "pps", "wakeup";

Where we repeat interrupt 120 for both "int2" and "wakeup", does you mean this?

> > >
> > > I can see a few ways to do this:
> > >
> > > The FEC driver already has quirks. Add a quirk to fec_imx8mq_info
> > > and fec_imx8qm_info to indicate these should use int2.
> 
> Bingo!
> 
> Note that if the device is wakeup capable, it should have a 'wakeup-source'
> property in this case.
> 
> > >
> > > or
> > >
> > > Documentation/devicetree/bindings/interrupt-controller/interrupts.tx
> > > t
> > >
> > >   b) two cells
> > >   ------------
> > >   The #interrupt-cells property is set to 2 and the first cell defines the
> > >   index of the interrupt within the controller, while the second cell is used
> > >   to specify any of the following flags:
> > >     - bits[3:0] trigger type and level flags
> > >         1 = low-to-high edge triggered
> > >         2 = high-to-low edge triggered
> > >         4 = active high level-sensitive
> > >         8 = active low level-sensitive
> > >
> > > You could add
> > >
> > >        18 = wakeup source
> 
> I'd be okay with this (though it should be a power of 2 number).
> 
> > >
> > > and extend to core to either do all the work for you, or tell you
> > > this interrupt is flagged as being a wakeup source. This solution
> > > has the advantage of it should be usable in other drivers.
> 
> Another option is couldn't you just enable all the interrupts as wakeup sources?
> Presumably, only one of them would trigger a wakeup.

Yes, another solution, I thought it but not implemented it as we had better let users know which
interrupt is wakeup capable.

Best Regards,
Joakim Zhang
> >
> > Thanks a lot for your comments first!
> >
> > I just look into the irq code, if we extend bit[5] to carry wakeup
> > info ( due to bit[4] is used for IRQ_TYPE_PROBE), then configure it in
> > the TYPE field of 'interrupts' property, so that interrupt controller would know
> which interrupt is wakeup capable.
> > I think there is no much work core would do, may just set this
> > interrupt wakup capable. Another functionality is driver side get this info to
> identify which mixed interrupt has wakeup capability, we can export symbol
> from kernel/irq/irqdomain.c.
> >
> > The intention is to let driver know which interrupt is wakeup capable,
> > I would choose to provider this in specific driver, instead of interrupt
> controller, it seems to me that others may all choose this solution for wakeup
> mixed interrupt.
> >
> > So I would prefer solution 1, it's easier and under-control. I can have a try if
> you strongly recommend solution 2.
> >
> > Best Regards,
> > Joakim Zhang
> > > 	  Andrew