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

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Date:   Sun, 6 Jan 2019 16:45:22 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Norbert Jurkeit <norbert.jurkeit@....de>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Frank Crawford <frank@...wford.emu.id.au>
Subject: Re: [PATCH net] net: phy: replace preliminary fix for PHY driver
 sometimes not binding to the device

On 29.12.2018 17:59, Norbert Jurkeit wrote:
> Am 29.12.18 um 16:44 schrieb Heiner Kallweit:
>>
>> I don't think this patch can have any impact on the issue. Maybe WoL is still active from previous test?
>> Manual WoL settings may survive a reboot, you can disable WoL by "ethtool -s <if> wol d".
> 
> In theory I agree, but we have seen before that it can not be predicted or logically explained which kernel build suffers from the issue or does not. WoL is definitely off. When it was enabled, the LED already turned on with the BIOS diagnostics screen and not at the end of the boot process as observed with the patched kernel.
> 
>>
>> What could be helpful in addition: I provided a patch with some debug output in comment 106
>> in the bug ticket (https://bugzilla.redhat.com/show_bug.cgi?id=1650984).
>> If you could apply this, trigger a fail scenario, and attach the full dmesg to the bug ticket.
> I just tried the Fedora kernel provided in comment 107. Unfortunately the fault neither shows up with this kernel nor with the stock Fedora kernel 4.19.12 it is based on. I will further try to find a kernel which fails to bring up the link AND provides some useful debug information but can't anticipate if and when.
>> Thanks a lot!
> You are welcome ;-)
> 
> 

Just by chance I came across the concept of MODULE_SOFTDEP. This is
basically in driver code what people did as a workaround manually in
the modprobe config files. It ensures that the PHY driver module is
loaded before the network driver. It's still a workaround but the
most elegant I can think of. I'm pretty sure this reliably avoids
the issue, but: could you please test?

If it works, then what I list below as one patch would be splitted:
1. add MODULE_SOFTDEP to r8169
2. remove preliminary fix

Thanks, Heiner


diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 298930d39..4c1485a42 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -706,6 +706,7 @@ module_param(use_dac, int, 0);
 MODULE_PARM_DESC(use_dac, "Enable PCI DAC. Unsafe on 32 bit PCI slot.");
 module_param_named(debug, debug.msg_enable, int, 0);
 MODULE_PARM_DESC(debug, "Debug verbosity level (0=none, ..., 16=all)");
+MODULE_SOFTDEP("pre: realtek");
 MODULE_LICENSE("GPL");
 MODULE_FIRMWARE(FIRMWARE_8168D_1);
 MODULE_FIRMWARE(FIRMWARE_8168D_2);
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 9560a2b84..80be72844 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2259,14 +2259,6 @@ int phy_driver_register(struct phy_driver *new_driver, struct module *owner)
 	new_driver->mdiodrv.driver.remove = phy_remove;
 	new_driver->mdiodrv.driver.owner = owner;
 
-	/* The following works around an issue where the PHY driver doesn't bind
-	 * to the device, resulting in the genphy driver being used instead of
-	 * the dedicated driver. The root cause of the issue isn't known yet
-	 * and seems to be in the base driver core. Once this is fixed we may
-	 * remove this workaround.
-	 */
-	new_driver->mdiodrv.driver.probe_type = PROBE_FORCE_SYNCHRONOUS;
-
 	retval = driver_register(&new_driver->mdiodrv.driver);
 	if (retval) {
 		pr_err("%s: Error %d in registering driver\n",
-- 
2.20.1