netdev - Re: [PATCH net] net: phy: replace preliminary fix for PHY driver sometimes not binding to the device

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Message-Id: <20181228.130210.1182302358435035456.davem@davemloft.net>
Date:   Fri, 28 Dec 2018 13:02:10 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     hkallweit1@...il.com
Cc:     andrew@...n.ch, f.fainelli@...il.com, gregkh@...uxfoundation.org,
        rafael@...nel.org, netdev@...r.kernel.org, norbert.jurkeit@....de,
        frank@...wford.emu.id.au
Subject: Re: [PATCH net] net: phy: replace preliminary fix for PHY driver
 sometimes not binding to the device

From: Heiner Kallweit <hkallweit1@...il.com>
Date: Mon, 24 Dec 2018 12:21:12 +0100

> phy_device_create() uses request_module() to load the PHY driver module
> based on the PHY ID of the device. There is some timing issue which
> sometimes prevents the PHY driver to bind to the device. In such cases
> the genphy driver is used what can cause problems if genphy isn't
> compatible with the respective PHY.
> It turned out that the first fix can fix the issue in some but not all
> cases. Moving the call to device_initialize() before the call to
> request_module() was reported to fix the issue.
> I can't explain where the root cause of the issue is and why this fix
> works. AFAICS device_initialize() just initializes the device struct
> w/o doing anything that could interfere with e.g. bus_add_driver().
> This patch removes the first preliminary fix attempt.
> 
> Reference:
> https://bugzilla.redhat.com/show_bug.cgi?id=1650984
> 
> Fixes: c85ddecae6e5 ("net: phy: add workaround for issue where PHY driver doesn't bind to the device")
> Tested-by: Norbert Jurkeit <norbert.jurkeit@....de>
> Tested-by: Frank Crawford <frank@...wford.emu.id.au>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>

I can't see any way this can make a difference.  I'm really stumped
and even if it did fix all of the issues people are seeing I wouldn't
want to apply this patch.

We need to know why, and put the why into the commit log message.

Thanks.