[PATCH net v4 0/5] net: phy: postpone PHY interrupts during sleep with MAC-managed PM

[Igor Velkov via B4 Relay]

When the MAC driver manages PHY PM, phylib never sets irq_suspended, and
a PHY interrupt during the sleep transition runs the PHY driver's
handler while the MDIO bus may be powered down. On Helios64 (dwmac-rk)
this hangs the board on suspend as well as on resume.

mac_managed_pm hands phy_suspend(), phy_resume() and the state machine
to the MAC driver, since commit fba863b81604 ("net: phy: make PHY PM
ops a no-op if MAC driver manages PHY PM"); the PHY interrupt stays
with phylib, and so does postponing it.

Patches 1-4 fix the postponing that phylib applies to other PHYs, so
that patch 5 can extend it to MAC-managed ones. Patch 1 moves the two
flags out of a bitfield they share with the link state written under
phydev->lock. Patch 2 lets only one run of the handler disable the line
when an edge reruns the IRQ thread. Patch 3 keeps that disable balanced
when phy_free_interrupt() runs during the transition. Patch 4 undoes
the postponing when a PHY PM callback fails. Patch 5 sets
irq_suspended for MAC-managed PHYs too and decides the wakeup event of
a postponed interrupt before the device that owns the MDIO bus
suspends.

Not covered: MDIO accesses from closing or opening the interface
during the transition, and a MAC resume that fails to power the bus
up. On a shared line, a postponed PHY interrupt disables the line for
its other users until the PHY resumes; patch 5 extends that to
MAC-managed PHYs.

With Wake-on-LAN, any postponed interrupt reports a system wakeup, so a
PHY that does not mask its link interrupt in suspend can abort suspend
when the MAC stops it. RTL8211F masks it when it is a wakeup source;
other PHYs were not tested. Tested only on Helios64 (dwmac-rk,
RTL8211F).

Changes in v4:
- new patches 2-4, one pre-existing defect each
- patch 2: an edge that reruns the IRQ thread no longer disables the
  line twice
- patch 3: phy_free_interrupt() during the transition keeps the line
  balanced (Sashiko on v3)
- patch 4: a failing PHY PM callback no longer leaves the interrupt
  postponed (Sashiko on v2 and v3)
- patch 5: the wakeup event is decided in mdio_bus_phy_suspend(), where
  phy_may_wakeup() can still read the PHY (Sashiko on v3); Fixes: now
  points at the stmmac commit that took its PHYs out of postponing
- v3 asked phylib or phylink_suspend(): phylib, as macb sets
  mac_managed_pm but suspends with phylink_stop()
- tests rerun on v4
- Link to v3: https://lore.kernel.org/r/20261029-b4-phylib-mac-pm-irq-v3-v3-0-5907045f3210@iav.lv

Not changed: a nested threaded PHY interrupt is not replayed
(irq_wake_thread() has no thread to wake), as before this series. Not
in this series: mdio_bus_phy_may_suspend() does not ask
phy_may_wakeup() about an attached PHY.

Changes in v3:
- with mac_managed_pm, a postponed interrupt signals a wakeup event only
  with Wake-on-LAN; with MAC power/wakeup enabled and no WoL, v2 aborted
  s2idle on Helios64 3 of 3 times, v3 0 of 3 (reported by Sashiko)
- phy_free_interrupt(): stop postponing and re-enable the line before
  free_irq(), not after it (reported by Sashiko)
- mdio_bus_phy_suspend() comment narrowed to the MDIO bus (reported by
  Sashiko)
- patch 1: Andrew suggested taking phydev->lock in phy_interrupt();
  the commit message says why that does not close the race
- tests rerun on v3
- Link to v2: https://lore.kernel.org/r/20261026045343.837889-1-iav@iav.lv

Signed-off-by: Igor Velkov <iav at iav.lv>
---
Igor Velkov (5):
      net: phy: move irq_suspended and irq_rerun out of the bitfield
      net: phy: disable the line of a postponed PHY interrupt only once
      net: phy: balance a postponed PHY interrupt when the interrupt is freed
      net: phy: stop postponing PHY interrupts when a PHY PM callback fails
      net: phy: postpone PHY interrupts during sleep with MAC-managed PM

 drivers/net/phy/phy.c        |  46 ++++++++++++----
 drivers/net/phy/phy_device.c | 125 ++++++++++++++++++++++++++++++++++---------
 include/linux/phy.h          |  36 ++++++++++---
 3 files changed, 164 insertions(+), 43 deletions(-)
---
base-commit: fcc00b15cb21a6de76826e5012b2c758505f5e65
change-id: 20261029-b4-phylib-mac-pm-irq-v3-f656d4e1c64f

Best regards,
-- 
Igor Velkov <iav at iav.lv>