On Fri, Jun 28, 2024 at 02:03:18PM +0800, Youwan Wang wrote:
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.
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.
I think the reason this is happening is because the PHY has WoL enabled
on it without the kernel/netdev driver being aware that WoL is enabled.
Thus, mdio_bus_phy_may_suspend() returns true, allowing the suspend to
happen, but then we find unexpectedly that WoL is enabled on the PHY.
However, whenever a user configures WoL, netdev->wol_enabled will be
set when _any_ WoL mode is enabled and cleared only if all WoL modes
are disabled.
Thus, what we have is a de-sync between the kernel state and hardware
state, leading to the suspend failing.
I don't see anything in the motorcomm driver that requires suspend
if WoL is enabled - yt8521_suspend() first checks to see whether WoL
is enabled, and exits if it is.
Andrew - how do you feel about reading the WoL state from the PHY and
setting netdev->wol_enabled if any WoL is enabled on the PHY? That
would mean that the netdev's WoL state is consistent with the PHY
whether or not the user has configured WoL.