[PATCH net] net: phy: Warn about incorrect mdio_bus_phy_resume() state

Florian Fainelli
2022-08-01T23:34:13Z

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>
---
drivers/net/phy/phy_device.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 46acddd865a7..608de5a94165 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -316,6 +316,12 @@ static __maybe_unused int mdio_bus_phy_resume(struct device *dev)

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;
--
2.25.1