Message-ID: <8d26c979-62ba-3263-2a13-3e872c535707@samsung.com>
Date:   Thu, 26 May 2022 12:34:40 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Lukas Wunner <lukas@...ner.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>
Cc:     netdev@...r.kernel.org,
        Steve Glendinning <steve.glendinning@...well.net>,
        UNGLinuxDriver@...rochip.com, Oliver Neukum <oneukum@...e.com>,
        Andre Edich <andre.edich@...rochip.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Martyn Welch <martyn.welch@...labora.com>,
        Gabriel Hojda <ghojda@...urs.ro>,
        Christoph Fritz <chf.fritz@...glemail.com>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>,
        Ferry Toth <fntoth@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH net] net: phy: Don't trigger state machine while in
 suspend

Hi Lukas,

On 26.05.2022 11:28, Lukas Wunner 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().
>
> 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.
>
> Fixes: 1ce8b37241ed ("usbnet: smsc95xx: Forward PHY interrupts to PHY driver to avoid polling")

I'm not sure if this is a right commit here. It revealed the issue, but 
it is not directly related to the net/phy code.

> Link: https://lore.kernel.org/netdev/a5315a8a-32c2-962f-f696-de9a26d30091@samsung.com/
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Lukas Wunner <lukas@...ner.de>

Tested-by: Marek Szyprowski <m.szyprowski@...sung.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;
>   

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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