[PATCH 5.15 058/244] net: phy: Warn about incorrect mdio_bus_phy_resume() state

Greg Kroah-Hartman
2022-08-23T09:49:05Z

From: Florian Fainelli <f.fainelli@gmail.com>

commit 744d23c71af39c7dc77ac7c3cac87ae86a181a85 upstream.

Calling mdio_bus_phy_resume() with neither the PHY state machine set to
PHY_HALTED nor phydev->mac_managed_pm set to true is a good indication
that we can produce a race condition looking like this:

CPU0 CPU1
bcmgenet_resume
-> phy_resume
-> phy_init_hw
-> phy_start
-> phy_resume
phy_start_aneg()
mdio_bus_phy_resume
-> phy_resume
-> phy_write(..., BMCR_RESET)
-> usleep() -> phy_read()

with the phy_resume() function triggering a PHY behavior that might have
to be worked around with (see bf8bfc4336f7 ("net: phy: broadcom: Fix
brcm_fet_config_init()") for instance) that ultimately leads to an error
reading from the PHY.

Fixes: fba863b81604 ("net: phy: make PHY PM ops a no-op if MAC driver manages PHY PM")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220801233403.258871-1-f.fainelli@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/phy/phy_device.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -315,6 +315,12 @@ static __maybe_unused int mdio_bus_phy_r

phydev->suspended_by_mdio_bus = 0;

+ /* If we managed to get here with the PHY state machine in a state other
+ * than PHY_HALTED this is an indication that something went wrong and
+ * we should most likely be using MAC managed PM and we are not.
+ */
+ WARN_ON(phydev->state != PHY_HALTED && !phydev->mac_managed_pm);
+
ret = phy_init_hw(phydev);
if (ret < 0)
return ret;