[net-next,v2] net: phy: phy_device: fix PHY WOL enabled, PM failed to suspend

[Youwan Wang]

>> If the PHY of the mido bus is enabled with Wake-on-LAN (WOL),
>> we cannot suspend the PHY. Although the WOL status has been
>> checked in phy_suspend(), returning -EBUSY(-16) would cause
>> the Power Management (PM) to fail to suspend. Since
>> phy_suspend() is an exported symbol (EXPORT_SYMBOL),
>> timely error reporting is needed. Therefore, an additional
>> check is performed here. If the PHY of the mido bus is enabled
>> with WOL, we skip calling phy_suspend() to avoid PM failure.
>>
>> Thank you all for your analysis.
>> I am using the Linux kernel version 6.6, the current system is
>> utilizing ACPI firmware. However, in terms of configuration,
>> the system only includes MAC layer configuration while lacking
>> PHY configuration. Furthermore, it has been observed that the
>> phydev->attached_dev is NULL
>>
>> Is it possible to add a judgment about netdev is NULL?
>> if (!netdev && phydev->wol_enabled &&
>>     !(phydrv->flags & PHY_ALWAYS_CALL_SUSPEND))

>Comments like this should be placed below the --- so they don't make
>it into the commit message.

>Why is phydev->attached_dev NULL? Was a MAC never attached to the PHY?
>Has the MAC disconnected the PHY as part of the suspend? It would be
>odd that a device being used for WoL would disconnect the PHY.

it has been observed that the phydev->attached_dev is NULL, phydev is
"stmmac-0:01", it not attached, but it will affect suspend and resume.
The actually attached "stmmac-0:00" will not dpm_run_callback():
mdio_bus_phy_suspend().

log:
[    5.932502] YT8521 Gigabit Ethernet stmmac-0:00: attached PHY driver
(mii_bus:phy_addr=stmmac-0:00, irq=POLL)
[    5.932512] YT8521 Gigabit Ethernet stmmac-0:01: attached PHY driver
(mii_bus:phy_addr=stmmac-0:01, irq=POLL)
[   24.566289] YT8521 Gigabit Ethernet stmmac-0:00: yt8521_read_status,
link down, media: UTP

>>
>> log:
>> [  322.631362] OOM killer disabled.
>> [  322.631364] Freezing remaining freezable tasks
>> [  322.632536] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
>> [  322.632540] printk: Suspending console(s) (use no_console_suspend to debug)
>> [  322.633052] YT8521 Gigabit Ethernet stmmac-0:01:
>> PM: dpm_run_callback(): mdio_bus_phy_suspend+0x0/0x110 [libphy] returns -16
>> [  322.633071] YT8521 Gigabit Ethernet stmmac-0:01:
>> PM: failed to suspend: error -16
>> [  322.669699] PM: Some devices failed to suspend, or early wake event detected
>> [  322.669949] OOM killer enabled.
>> [  322.669951] Restarting tasks ... done.
>> [  322.671008] random: crng reseeded on system resumption
>> [  322.671014] PM: suspend exit
>>
>> If the YT8521 driver adds phydrv->flags, ask the YT8521 driver to process
>> WOL at suspend and resume time, the phydev->suspended_by_mdio_bus=1
>> flag would cause the resume failure.
>>
>> log:
>> [  260.814763] YT8521 Gigabit Ethernet stmmac-0:01:
>> PM: dpm_run_callback():mdio_bus_phy_resume+0x0/0x160 [libphy] returns -95
>> [  260.814782] YT8521 Gigabit Ethernet stmmac-0:01:
>> PM: failed to resume: error -95

>-95 is EOPNOTSUPP. Where is that coming from?

yt8511_config_init() -> ret = -EOPNOTSUPP;

Signed-off-by: Youwan Wang <youwan@xxxxxxxxxxxx>
---
 drivers/net/phy/phy_device.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 2ce74593d6e4..0564decf701f 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -270,6 +270,7 @@ static DEFINE_MUTEX(phy_fixup_lock);
 
 static bool mdio_bus_phy_may_suspend(struct phy_device *phydev)
 {
+	struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
 	struct device_driver *drv = phydev->mdio.dev.driver;
 	struct phy_driver *phydrv = to_phy_driver(drv);
 	struct net_device *netdev = phydev->attached_dev;
@@ -277,6 +278,15 @@ static bool mdio_bus_phy_may_suspend(struct phy_device *phydev)
 	if (!drv || !phydrv->suspend)
 		return false;
 
+	/* If the PHY on the mido bus is not attached but has WOL enabled
+	 * we cannot suspend the PHY.
+	 */
+	phy_ethtool_get_wol(phydev, &wol);
+	phydev->wol_enabled = !!(wol.wolopts);
+	if (!netdev && phydev->wol_enabled &&
+	    !(phydrv->flags & PHY_ALWAYS_CALL_SUSPEND))
+		return false;
+
 	/* PHY not attached? May suspend if the PHY has not already been
 	 * suspended as part of a prior call to phy_disconnect() ->
 	 * phy_detach() -> phy_suspend() because the parent netdev might be the
-- 
2.25.1