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SubjectRe: [PATCH net v2 1/1] net: phy: Don't trigger state machine while in suspend
On Wed, Jun 8, 2022 at 11:57 AM Lukas Wunner <lukas@wunner.de> wrote:
>
> 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>

Looks reasonable to me.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
> 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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