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Date:   Mon, 21 Jun 2021 15:09:06 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Jian-Hong Pan <jhp@endlessos.org>
Cc:     Doug Berger <opendmb@gmail.com>,
        Florian Fainelli <f.fainelli@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
Subject: Re: [PATCH] net: bcmgenet: Fix attaching to PYH failed on RPi 4B
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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.

	Andrew