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Subject[PATCH net v2 1/1] net: phy: Don't trigger state machine while in suspend
Upon system sleep, mdio_bus_phy_suspend() stops the phy_state_machine(),
but subsequent interrupts may retrigger it:

They may have been left enabled to facilitate wakeup and are not
quiesced until the ->suspend_noirq() phase. Unwanted interrupts may
hence occur between mdio_bus_phy_suspend() and dpm_suspend_noirq(),
as well as between dpm_resume_noirq() and mdio_bus_phy_resume().

Retriggering the phy_state_machine() through an interrupt is not only
undesirable for the reason given in mdio_bus_phy_suspend() (freezing it
midway with phydev->lock held), but also because the PHY may be
inaccessible after it's suspended: Accesses to USB-attached PHYs are
blocked once usb_suspend_both() clears the can_submit flag and PHYs on
PCI network cards may become inaccessible upon suspend as well.

Amend phy_interrupt() to avoid triggering the state machine if the PHY
is suspended. Signal wakeup instead if the attached net_device or its
parent has been configured as a wakeup source. (Those conditions are
identical to mdio_bus_phy_may_suspend().) Postpone handling of the
interrupt until the PHY has resumed.

Before stopping the phy_state_machine() in mdio_bus_phy_suspend(),
wait for a concurrent phy_interrupt() to run to completion. That is
necessary because phy_interrupt() may have checked the PHY's suspend
status before the system sleep transition commenced and it may thus
retrigger the state machine after it was stopped.

Likewise, after re-enabling interrupt handling in mdio_bus_phy_resume(),
wait for a concurrent phy_interrupt() to complete to ensure that
interrupts which it postponed are properly rerun.

Link: https://lore.kernel.org/netdev/a5315a8a-32c2-962f-f696-de9a26d30091@samsung.com/
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
---
drivers/net/phy/phy.c | 23 +++++++++++++++++++++++
drivers/net/phy/phy_device.c | 23 +++++++++++++++++++++++
include/linux/phy.h | 6 ++++++
3 files changed, 52 insertions(+)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index ef62f357b76d..8d3ee3a6495b 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -31,6 +31,7 @@
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/atomic.h>
+#include <linux/suspend.h>
#include <net/netlink.h>
#include <net/genetlink.h>
#include <net/sock.h>
@@ -976,6 +977,28 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
struct phy_driver *drv = phydev->drv;
irqreturn_t ret;

+ /* Wakeup interrupts may occur during a system sleep transition.
+ * Postpone handling until the PHY has resumed.
+ */
+ if (IS_ENABLED(CONFIG_PM_SLEEP) && phydev->irq_suspended) {
+ struct net_device *netdev = phydev->attached_dev;
+
+ if (netdev) {
+ struct device *parent = netdev->dev.parent;
+
+ if (netdev->wol_enabled)
+ pm_system_wakeup();
+ else if (device_may_wakeup(&netdev->dev))
+ pm_wakeup_dev_event(&netdev->dev, 0, true);
+ else if (parent && device_may_wakeup(parent))
+ pm_wakeup_dev_event(parent, 0, true);
+ }
+
+ phydev->irq_rerun = 1;
+ disable_irq_nosync(irq);
+ return IRQ_HANDLED;
+ }
+
mutex_lock(&phydev->lock);
ret = drv->handle_interrupt(phydev);
mutex_unlock(&phydev->lock);
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 431a8719c635..46acddd865a7 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -278,6 +278,15 @@ static __maybe_unused int mdio_bus_phy_suspend(struct device *dev)
if (phydev->mac_managed_pm)
return 0;

+ /* Wakeup interrupts may occur during the system sleep transition when
+ * the PHY is inaccessible. Set flag to postpone handling until the PHY
+ * has resumed. Wait for concurrent interrupt handler to complete.
+ */
+ if (phy_interrupt_is_valid(phydev)) {
+ phydev->irq_suspended = 1;
+ synchronize_irq(phydev->irq);
+ }
+
/* We must stop the state machine manually, otherwise it stops out of
* control, possibly with the phydev->lock held. Upon resume, netdev
* may call phy routines that try to grab the same lock, and that may
@@ -315,6 +324,20 @@ static __maybe_unused int mdio_bus_phy_resume(struct device *dev)
if (ret < 0)
return ret;
no_resume:
+ if (phy_interrupt_is_valid(phydev)) {
+ phydev->irq_suspended = 0;
+ synchronize_irq(phydev->irq);
+
+ /* Rerun interrupts which were postponed by phy_interrupt()
+ * because they occurred during the system sleep transition.
+ */
+ if (phydev->irq_rerun) {
+ phydev->irq_rerun = 0;
+ enable_irq(phydev->irq);
+ irq_wake_thread(phydev->irq, phydev);
+ }
+ }
+
if (phydev->attached_dev && phydev->adjust_link)
phy_start_machine(phydev);

diff --git a/include/linux/phy.h b/include/linux/phy.h
index 508f1149665b..b09f7d36cff2 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -572,6 +572,10 @@ struct macsec_ops;
* @mdix_ctrl: User setting of crossover
* @pma_extable: Cached value of PMA/PMD Extended Abilities Register
* @interrupts: Flag interrupts have been enabled
+ * @irq_suspended: Flag indicating PHY is suspended and therefore interrupt
+ * handling shall be postponed until PHY has resumed
+ * @irq_rerun: Flag indicating interrupts occurred while PHY was suspended,
+ * requiring a rerun of the interrupt handler after resume
* @interface: enum phy_interface_t value
* @skb: Netlink message for cable diagnostics
* @nest: Netlink nest used for cable diagnostics
@@ -626,6 +630,8 @@ struct phy_device {

/* Interrupts are enabled */
unsigned interrupts:1;
+ unsigned irq_suspended:1;
+ unsigned irq_rerun:1;

enum phy_state state;

--
2.35.2
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