linux-kernel - Re: [PATCH net-next v1 4/4] net: phy: mxl-gpy: disable interrupts on GPY215 by default

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Date:   Tue, 20 Dec 2022 22:39:15 +0100
From:   Michael Walle <michael@...le.cc>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Xu Liang <lxu@...linear.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v1 4/4] net: phy: mxl-gpy: disable interrupts on
 GPY215 by default

Am 2022-12-20 14:33, schrieb Andrew Lunn:
>> > > > I think a better place for this test is in gpy_config_intr(), return
>> > > > -EOPNOTSUPP. phy_enable_interrupts() failing should then cause
>> > > > phy_request_interrupt() to use polling.
>> > >
>> > > Which will then print a warning, which might be misleading.
>> > > Or we disable the warning if -EOPNOTSUPP is returned?
>> >
>> > Disabling the warning is the right thing to do.
>> 
>> There is more to this. .config_intr() is also used in
>> phy_init_hw() and phy_drv_supports_irq(). The latter would
>> still return true in our case. I'm not sure that is correct.
>> 
>> After trying your suggestion, I'm still in favor of somehow
>> tell the phy core to force polling mode during probe() of the
>> driver.
> 
> The problem is that the MAC can set the interrupt number after the PHY
> probe has been called. e.g.
> 
> https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c#L524
> 
> The interrupt needs to be set by the time the PHY is connected to the
> MAC, which is often in the MAC open method, much later than the PHY
> probe.

Ok, then phydev->irq should be updated within the phy_attach_direct().
Something like the following:

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index e865be3d7f01..c6c5830f5214 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1537,6 +1537,14 @@ int phy_attach_direct(struct net_device *dev, 
struct phy_device *phydev,

         phydev->interrupts = PHY_INTERRUPT_DISABLED;

+       /* PHYs can request to use poll mode even though they have an
+        * associated interrupt line. This could be the case if they
+        * detect a broken interrupt handling.
+        */
+       if (phydev->drv->force_polling_mode &&
+           phydev->drv->force_polling_mode(phydev))
+               phydev->irq = PHY_POLL;
+
         /* Port is set to PORT_TP by default and the actual PHY driver 
will set
          * it to different value depending on the PHY configuration. If 
we have
          * the generic PHY driver we can't figure it out, thus set the 
old

That callback could be too specifc, I don't know. We could also have
phydev->drv->pre_attach() which then can update the phydev->irq itself.

Btw. the phy_attached_info() in the stmmac seems to be a leftover
from before the phylink conversion. phylink will print a similar info
but when the PHY is actually attached.

-michael