linux-kernel - Re: [PATCH] of_mdio: Fix broken PHY IRQ in case of probe deferral

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Message-ID: <CAMuHMdW_ZSn_nXSNRTHQwFioRD5UTotxKgm1eMqAP06n+cWv+g@mail.gmail.com>
Date:   Thu, 18 May 2017 18:13:24 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Florian Fainelli <f.fainelli@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of_mdio: Fix broken PHY IRQ in case of probe deferral

Hi Andrew,

On Thu, May 18, 2017 at 6:09 PM, Andrew Lunn <andrew@...n.ch> wrote:
> On Thu, May 18, 2017 at 02:59:05PM +0200, Geert Uytterhoeven wrote:
>> If an Ethernet PHY is initialized before the interrupt controller it is
>> connected to, a message like the following is printed:
>>
>>     irq: no irq domain found for /interrupt-controller@...c0000 !
>>
>> However, the actual error is ignored, leading to a non-functional (-1)
>> PHY interrupt later:
>>
>>     Micrel KSZ8041RNLI ee700000.ethernet-ffffffff:01: attached PHY driver [Micrel KSZ8041RNLI] (mii_bus:phy_addr=ee700000.ethernet-ffffffff:01, irq=-1)
>>
>> Depending on whether the PHY driver will fall back to polling, Ethernet
>> may or may not work.
>>
>> To fix this:
>>   1. Switch of_mdiobus_register_phy() from irq_of_parse_and_map() to
>>      of_irq_get().
>>      Unlike the former, the latter returns -EPROBE_DEFER if the
>>      interrupt controller is not yet available, so this condition can be
>>      detected.
>>      Other errors are handled the same as before, i.e. use the passed
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>      mdio->irq[addr] as interrupt.
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>   2. Propagate and handle errors from of_mdiobus_register_phy() and
>>      of_mdiobus_register_device().
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
>> ---
>> Seen on r8a7791/koelsch when using the new CPG/MSSR clock driver.
>> I assume it always happened on RZ/G1 in mainline.
>> ---
>>  drivers/of/of_mdio.c | 39 +++++++++++++++++++++++++++------------
>>  1 file changed, 27 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
>> index 7e4c80f9b6cda0d3..f9ac2893f56184be 100644
>> --- a/drivers/of/of_mdio.c
>> +++ b/drivers/of/of_mdio.c
>> @@ -44,7 +44,7 @@ static int of_get_phy_id(struct device_node *device, u32 *phy_id)
>>       return -EINVAL;
>>  }
>>
>> -static void of_mdiobus_register_phy(struct mii_bus *mdio,
>> +static int of_mdiobus_register_phy(struct mii_bus *mdio,
>>                                   struct device_node *child, u32 addr)
>>  {
>>       struct phy_device *phy;
>> @@ -60,9 +60,13 @@ static void of_mdiobus_register_phy(struct mii_bus *mdio,
>>       else
>>               phy = get_phy_device(mdio, addr, is_c45);
>>       if (IS_ERR(phy))
>> -             return;
>> +             return PTR_ERR(phy);
>>
>> -     rc = irq_of_parse_and_map(child, 0);
>> +     rc = of_irq_get(child, 0);
>> +     if (rc == -EPROBE_DEFER) {
>> +             phy_device_free(phy);
>> +             return rc;
>> +     }
>
> Maybe this should be consistent. All other places there is an error,
> you return it. Here however, you only return the error if it is
> EPROBE_DEFER.

That's because of the "else" branch in the code below:

        if (rc > 0) {
                phy->irq = rc;
                mdio->irq[addr] = rc;
        } else {
                phy->irq = mdio->irq[addr];
        }

cfr. the marked part of the patch description.
I didn't want to change that behavior, as it's not clear to me why it's handled
that way.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds