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Subject: Re: [PATCH] net: bcmgenet: Fix attaching to PYH failed on RPi 4B
From:   Florian Fainelli <f.fainelli@gmail.com>
To:     Andrew Lunn <andrew@lunn.ch>, Jian-Hong Pan <jhp@endlessos.org>
Cc:     Doug Berger <opendmb@gmail.com>,
        Stefan Wahren <stefan.wahren@i2se.com>,
        bcm-kernel-feedback-list@broadcom.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux@endlessos.org,
        linux-rpi-kernel@lists.infradead.org
References: <20210621103310.186334-1-jhp@endlessos.org>
 <YNCPcmEPuwdwoLto@lunn.ch> <35f4baae-a6e1-c87d-279c-74f8c18bb5d1@gmail.com>
Message-ID: <0f0b2647-ba50-a247-3b6e-aed1e1c77f67@gmail.com>
Date:   Mon, 21 Jun 2021 09:47:21 -0700
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On 6/21/21 9:37 AM, Florian Fainelli wrote:
> On 6/21/21 6:09 AM, Andrew Lunn wrote:
>> On Mon, Jun 21, 2021 at 06:33:11PM +0800, Jian-Hong Pan wrote:
>>> The Broadcom UniMAC MDIO bus comes too late. So, GENET cannot find the
>>> ethernet PHY on UniMAC MDIO bus. This leads GENET fail to attach the
>>> PHY.
>>>
>>> bcmgenet fd580000.ethernet: GENET 5.0 EPHY: 0x0000
>>> ...
>>> could not attach to PHY
>>> bcmgenet fd580000.ethernet eth0: failed to connect to PHY
>>> uart-pl011 fe201000.serial: no DMA platform data
>>> libphy: bcmgenet MII bus: probed
>>> ...
>>> unimac-mdio unimac-mdio.-19: Broadcom UniMAC MDIO bus
>>>
>>> This patch makes GENET try to connect the PHY up to 3 times. Also, waits
>>> a while between each time for mdio-bcm-unimac module's loading and
>>> probing.
>>
>> Don't loop. Return -EPROBE_DEFER. The driver core will then probed the
>> driver again later, by which time, the MDIO bus driver should of
>> probed.
> 
> This is unlikely to work because GENET register the mdio-bcm-unimac
> platform device so we will likely run into a chicken and egg problem,
> though surprisingly I have not seen this on STB platforms where GENET is
> used, I will try building everything as a module like you do. Can you
> see if the following helps:
> 
> diff --git a/drivers/net/mdio/mdio-bcm-unimac.c
> b/drivers/net/mdio/mdio-bcm-unimac.c
> index bfc9be23c973..d1844ef3724a 100644
> --- a/drivers/net/mdio/mdio-bcm-unimac.c
> +++ b/drivers/net/mdio/mdio-bcm-unimac.c
> @@ -351,6 +351,7 @@ static struct platform_driver unimac_mdio_driver = {
>                 .pm = &unimac_mdio_pm_ops,
>         },
>         .probe  = unimac_mdio_probe,
> +       .probe_type = PROBE_FORCE_SYNCHRONOUS,
>         .remove = unimac_mdio_remove,
>  };
>  module_platform_driver(unimac_mdio_driver);

This won't build try this instead:

diff --git a/drivers/net/mdio/mdio-bcm-unimac.c
b/drivers/net/mdio/mdio-bcm-unimac.c
index bfc9be23c973..53fecb53cd65 100644
--- a/drivers/net/mdio/mdio-bcm-unimac.c
+++ b/drivers/net/mdio/mdio-bcm-unimac.c
@@ -349,6 +349,7 @@ static struct platform_driver unimac_mdio_driver = {
                .name = UNIMAC_MDIO_DRV_NAME,
                .of_match_table = unimac_mdio_ids,
                .pm = &unimac_mdio_pm_ops,
+               .probe_type = PROBE_FORCE_SYNCHRONOUS,
        },
        .probe  = unimac_mdio_probe,
        .remove = unimac_mdio_remove,
-- 
Florian