netdev - Re: RE: RE: [PATCH net-next 07/13] net: fec: fec_probe(): update quirk: bring IRQs in correct order

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Message-ID: <20241017-manipulative-dove-of-renovation-88d00b-mkl@pengutronix.de>
Date: Thu, 17 Oct 2024 12:21:10 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Wei Fang <wei.fang@....com>
Cc: Shenwei Wang <shenwei.wang@....com>, 
	Clark Wang <xiaoning.wang@....com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com>, 
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: RE: RE: [PATCH net-next 07/13] net: fec: fec_probe(): update
 quirk: bring IRQs in correct order

On 17.10.2024 07:43:55, Wei Fang wrote:
> > > > Subject: [PATCH net-next 07/13] net: fec: fec_probe(): update quirk: bring
> > IRQs
> > > > in correct order
> > > >
> > > > With i.MX8MQ and compatible SoCs, the order of the IRQs in the device
> > > > tree is not optimal. The driver expects the first three IRQs to match
> > > > their corresponding queue, while the last (fourth) IRQ is used for the
> > > > PPS:
> > > >
> > > > - 1st IRQ: "int0": queue0 + other IRQs
> > > > - 2nd IRQ: "int1": queue1
> > > > - 3rd IRQ: "int2": queue2
> > > > - 4th IRQ: "pps": pps
> > > >
> > > > However, the i.MX8MQ and compatible SoCs do not use the
> > > > "interrupt-names" property and specify the IRQs in the wrong order:
> > > >
> > > > - 1st IRQ: queue1
> > > > - 2nd IRQ: queue2
> > > > - 3rd IRQ: queue0 + other IRQs
> > > > - 4th IRQ: pps
> > > >
> > > > First rename the quirk from FEC_QUIRK_WAKEUP_FROM_INT2 to
> > > > FEC_QUIRK_INT2_IS_MAIN_IRQ, to better reflect it's functionality.
> > > >
> > > > If the FEC_QUIRK_INT2_IS_MAIN_IRQ quirk is active, put the IRQs back
> > > > in the correct order, this is done in fec_probe().
> > > >
> > >
> > > I think FEC_QUIRK_INT2_IS_MAIN_IRQ or FEC_QUIRK_WAKEUP_FROM_INT2
> > > is *NO* needed anymore. Actually, INT2 is also the main IRQ for i.MX8QM
> > and
> > > its compatible SoCs, but i.MX8QM uses a different solution. I don't know
> > why
> > > there are two different ways of doing it, as I don't know the history. But you
> > can
> > > refer to the solution of i.MX8QM, which I think is more suitable.
> > >
> > > See arch/arm64/boot/dts/freescale/imx8-ss-conn.dtsi, the IRQ 258 is
> > > placed first.
> > 
> > Yes, that is IMHO the correct description of the IP core, but the
> > i.MX8M/N/Q DTS have the wrong order of IRQs. And for compatibility
> > reasons (fixed DTS with old driver) it's IMHO not possible to change the
> > DTS.
> > 
> 
> I don't think it is a correct behavior for old drivers to use new DTBs or new
> drivers to use old DTBs. Maybe you are correct, Frank also asked the same
> question, let's see how Frank responded.

DTBs should be considered stable ABI.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
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