netdev - Re: [PATCH net-next 03/14] net: stmmac: remove SGMII/RGMII/SMII interrupt handling

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Message-ID: <aPAcRNeFa5heydq7@shell.armlinux.org.uk>
Date: Wed, 15 Oct 2025 23:12:20 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Abhishek Chauhan <quic_abchauha@...cinc.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
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	Andrew Lunn <andrew+netdev@...n.ch>,
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	Yu-Chun Lin <eleanor15x@...il.com>
Subject: Re: [PATCH net-next 03/14] net: stmmac: remove SGMII/RGMII/SMII
 interrupt handling

On Wed, Oct 15, 2025 at 11:35:40PM +0200, Andrew Lunn wrote:
> On Wed, Oct 15, 2025 at 03:20:12PM +0100, Russell King (Oracle) wrote:
> > Now that the only use for the interrupt is to clear it and increment a
> > statistic counter (which is not that relevant anymore) remove all this
> > code and ensure that the interrupt remains disabled to avoid a stuck
> > interrupt.
> 
> Will this interrupt come back later, as part of the PCS? Or will the
> PCS be polled?

It depends whether it has any users - given the scrappy nature of all
this, and the fact it's never been properly implemented, I need to
hear from the platform glue people to really know what's going on.

Right now, all I'm doing is removing loads of code that has been proven
to be broken, and re-implementing what is left in a way that will work
for people who are using the internal PCS (in other words, where the
STMMAC_FLAG_HAS_INTEGRATED_PCS was set which disabled much of the
broken code anyway.)

> This leaves this counter unused, as you said. It does not look trivial
> to remove it, it is part of the statistics ABI. But if the interrupt
> comes back in a later patch, this counter could also be brought back
> to life?

Sadly, it's not quite unused - see dwmac-sun8i.c:

        if (v & EMAC_RGMII_STA_INT)
                x->irq_rgmii_n++;

This is more than glue, but is almost an entire core implementation as
well - the original commit introducing it says:

    The dwmac-sun8i is a heavy hacked version of stmmac hardware by
    allwinner.
    In fact the only common part is the descriptor management and the first
    register function.

So, rather than remove the statistic entirely, as I'm not touching this
hacked version, I decided to keep the statistic counter as there is
still something using it.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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