[PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[Frank Li]

reproduce steps
 1. flood ping from other machine
 	ping -f -s 41000 IP
 2. run below script
    while [ 1 ]; do ethtool -s eth0 autoneg off;
    sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;

You can see oops in one hour.

The reason is fec_restart clear BD but NAPI may use it.
The solution is disable NAPI and stop xmit when reset BD.
disable NAPI may sleep, so fec_restart can't be call in
atomic context.

Signed-off-by: Frank Li <Frank.Li@freescale.com>
---
Change from v1 to v2
 * Add netif_tx_lock(ndev) to avoid xmit runing when reset hardware
Change from v2 to v3
 * Move put real statements after function variable declarations according to David's comments
 * Remove lock in adjust_link according to Lucas Stach's comments
 
 drivers/net/ethernet/freescale/fec.c |   42 +++++++++++++++++++++++++---------
 drivers/net/ethernet/freescale/fec.h |    3 +-
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec.c b/drivers/net/ethernet/freescale/fec.c
index 73195f6..5a9345c 100644
--- a/drivers/net/ethernet/freescale/fec.c
+++ b/drivers/net/ethernet/freescale/fec.c
@@ -407,6 +407,12 @@ fec_restart(struct net_device *ndev, int duplex)
 	u32 rcntl = OPT_FRAME_SIZE | 0x04;
 	u32 ecntl = 0x2; /* ETHEREN */
 
+	if (netif_running(ndev)) {
+		napi_disable(&fep->napi);
+		netif_stop_queue(ndev);
+		netif_tx_lock(ndev);
+	}
+
 	/* Whack a reset.  We should wait for this. */
 	writel(1, fep->hwp + FEC_ECNTRL);
 	udelay(10);
@@ -559,6 +565,12 @@ fec_restart(struct net_device *ndev, int duplex)
 
 	/* Enable interrupts we wish to service */
 	writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
+
+	if (netif_running(ndev)) {
+		napi_enable(&fep->napi);
+		netif_wake_queue(ndev);
+		netif_tx_unlock(ndev);
+	}
 }
 
 static void
@@ -598,8 +610,20 @@ fec_timeout(struct net_device *ndev)
 
 	ndev->stats.tx_errors++;
 
-	fec_restart(ndev, fep->full_duplex);
-	netif_wake_queue(ndev);
+	fep->timeout = 1;
+	schedule_delayed_work(&fep->delay_work, msecs_to_jiffies(1));
+}
+
+static void fec_enet_work(struct work_struct *work)
+{
+	struct fec_enet_private *fep =
+		container_of(work, struct fec_enet_private, delay_work.work);
+
+	if (fep->timeout) {
+		fep->timeout = 0;
+		fec_restart(fep->netdev, fep->full_duplex);
+		netif_wake_queue(fep->netdev);
+	}
 }
 
 static void
@@ -970,16 +994,12 @@ static void fec_enet_adjust_link(struct net_device *ndev)
 {
 	struct fec_enet_private *fep = netdev_priv(ndev);
 	struct phy_device *phy_dev = fep->phy_dev;
-	unsigned long flags;
-
 	int status_change = 0;
 
-	spin_lock_irqsave(&fep->hw_lock, flags);
-
 	/* Prevent a state halted on mii error */
 	if (fep->mii_timeout && phy_dev->state == PHY_HALTED) {
 		phy_dev->state = PHY_RESUMING;
-		goto spin_unlock;
+		goto exit;
 	}
 
 	if (phy_dev->link) {
@@ -995,7 +1015,6 @@ static void fec_enet_adjust_link(struct net_device *ndev)
 			fep->speed = phy_dev->speed;
 			status_change = 1;
 		}
-
 		/* if any of the above changed restart the FEC */
 		if (status_change)
 			fec_restart(ndev, phy_dev->duplex);
@@ -1007,11 +1026,10 @@ static void fec_enet_adjust_link(struct net_device *ndev)
 		}
 	}
 
-spin_unlock:
-	spin_unlock_irqrestore(&fep->hw_lock, flags);
-
+exit:
 	if (status_change)
 		phy_print_status(phy_dev);
+
 }
 
 static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
@@ -1882,6 +1900,7 @@ fec_probe(struct platform_device *pdev)
 	if (ret)
 		goto failed_register;
 
+	INIT_DELAYED_WORK(&fep->delay_work, fec_enet_work);
 	return 0;
 
 failed_register:
@@ -1918,6 +1937,7 @@ fec_drv_remove(struct platform_device *pdev)
 	struct resource *r;
 	int i;
 
+	cancel_delayed_work_sync(&fep->delay_work);
 	unregister_netdev(ndev);
 	fec_enet_mii_remove(fep);
 	del_timer_sync(&fep->time_keep);
diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
index eb43729..a367b21 100644
--- a/drivers/net/ethernet/freescale/fec.h
+++ b/drivers/net/ethernet/freescale/fec.h
@@ -260,7 +260,8 @@ struct fec_enet_private {
 	int hwts_rx_en;
 	int hwts_tx_en;
 	struct timer_list time_keep;
-
+	struct delayed_work delay_work;
+	int timeout;
 };
 
 void fec_ptp_init(struct net_device *ndev, struct platform_device *pdev);
-- 
1.7.1

Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[David Miller]

From: Frank Li <Frank.Li@freescale.com>
Date: Thu, 2 May 2013 08:55:38 +0800

> reproduce steps
>  1. flood ping from other machine
>  	ping -f -s 41000 IP
>  2. run below script
>     while [ 1 ]; do ethtool -s eth0 autoneg off;
>     sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;
> 
> You can see oops in one hour.
> 
> The reason is fec_restart clear BD but NAPI may use it.
> The solution is disable NAPI and stop xmit when reset BD.
> disable NAPI may sleep, so fec_restart can't be call in
> atomic context.
> 
> Signed-off-by: Frank Li <Frank.Li@freescale.com>

Please respin this against the current 'net' tree.

Thanks!

Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[Frank Li]

2013/5/3 David Miller <davem@davemloft.net>:
> From: Frank Li <Frank.Li@freescale.com>
> Date: Thu, 2 May 2013 08:55:38 +0800
>
>> reproduce steps
>>  1. flood ping from other machine
>>       ping -f -s 41000 IP
>>  2. run below script
>>     while [ 1 ]; do ethtool -s eth0 autoneg off;
>>     sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;
>>
>> You can see oops in one hour.
>>
>> The reason is fec_restart clear BD but NAPI may use it.
>> The solution is disable NAPI and stop xmit when reset BD.
>> disable NAPI may sleep, so fec_restart can't be call in
>> atomic context.
>>
>> Signed-off-by: Frank Li <Frank.Li@freescale.com>
>
> Please respin this against the current 'net' tree.

MX6 can't bootup at net and net-next tree.
I am identifying the reason.

>
> Thanks!

Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[Lucas Stach]

Hi Frank,

Am Donnerstag, den 02.05.2013, 08:55 +0800 schrieb Frank Li:
> reproduce steps
>  1. flood ping from other machine
>  	ping -f -s 41000 IP
>  2. run below script
>     while [ 1 ]; do ethtool -s eth0 autoneg off;
>     sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;
> 
> You can see oops in one hour.
> 
> The reason is fec_restart clear BD but NAPI may use it.
> The solution is disable NAPI and stop xmit when reset BD.
> disable NAPI may sleep, so fec_restart can't be call in
> atomic context.
> 
> Signed-off-by: Frank Li <Frank.Li@freescale.com>
> ---
> Change from v1 to v2
>  * Add netif_tx_lock(ndev) to avoid xmit runing when reset hardware
> Change from v2 to v3
>  * Move put real statements after function variable declarations according to David's comments
>  * Remove lock in adjust_link according to Lucas Stach's comments
>  
>  drivers/net/ethernet/freescale/fec.c |   42 +++++++++++++++++++++++++---------
>  drivers/net/ethernet/freescale/fec.h |    3 +-
>  2 files changed, 33 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec.c b/drivers/net/ethernet/freescale/fec.c
> index 73195f6..5a9345c 100644
> --- a/drivers/net/ethernet/freescale/fec.c
> +++ b/drivers/net/ethernet/freescale/fec.c
> @@ -407,6 +407,12 @@ fec_restart(struct net_device *ndev, int duplex)
>  	u32 rcntl = OPT_FRAME_SIZE | 0x04;
>  	u32 ecntl = 0x2; /* ETHEREN */
>  
> +	if (netif_running(ndev)) {
> +		napi_disable(&fep->napi);
> +		netif_stop_queue(ndev);
> +		netif_tx_lock(ndev);
> +	}
> +
You did not address the comment from Ben Hutchings here. To make sure we
are not triggering the netdev watchdog immediately when calling
netif_stop_queue() we must call netif_device_detach() when entering the
fec_restart and netif_device_attach() when leaving.

fec_restart gets called when duplex or phy speed changes, not only in
response to a link up/down change.

>  	/* Whack a reset.  We should wait for this. */
>  	writel(1, fep->hwp + FEC_ECNTRL);
>  	udelay(10);
> @@ -559,6 +565,12 @@ fec_restart(struct net_device *ndev, int duplex)
>  
>  	/* Enable interrupts we wish to service */
>  	writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
> +
> +	if (netif_running(ndev)) {
> +		napi_enable(&fep->napi);
> +		netif_wake_queue(ndev);
> +		netif_tx_unlock(ndev);
> +	}
>  }
>  
>  static void
> @@ -598,8 +610,20 @@ fec_timeout(struct net_device *ndev)
>  
>  	ndev->stats.tx_errors++;
>  
> -	fec_restart(ndev, fep->full_duplex);
> -	netif_wake_queue(ndev);
> +	fep->timeout = 1;
> +	schedule_delayed_work(&fep->delay_work, msecs_to_jiffies(1));
> +}
Okay, I understand you want to reuse this workqueue to do other things
which might require delayed work so a delay workqueue is fine, but
really use a delay of 0 here.

schedule_delayed_work() internally calls down to queue_delayed_work_on()
where the documentation states: "If delay is zero and dwork is idle, it
will be scheduled for immediate execution.", so this is the right thing
to do here.

> +
> +static void fec_enet_work(struct work_struct *work)
> +{
> +	struct fec_enet_private *fep =
> +		container_of(work, struct fec_enet_private, delay_work.work);
> +
> +	if (fep->timeout) {
> +		fep->timeout = 0;
> +		fec_restart(fep->netdev, fep->full_duplex);
> +		netif_wake_queue(fep->netdev);
> +	}
>  }
>  
>  static void
> @@ -970,16 +994,12 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>  {
>  	struct fec_enet_private *fep = netdev_priv(ndev);
>  	struct phy_device *phy_dev = fep->phy_dev;
> -	unsigned long flags;
> -
>  	int status_change = 0;
>  
> -	spin_lock_irqsave(&fep->hw_lock, flags);
> -
>  	/* Prevent a state halted on mii error */
>  	if (fep->mii_timeout && phy_dev->state == PHY_HALTED) {
>  		phy_dev->state = PHY_RESUMING;
> -		goto spin_unlock;
> +		goto exit;
If we bail out here there is zero chance that we detect a link change,
so drop the label and just return here.

>  	}
>  
>  	if (phy_dev->link) {
> @@ -995,7 +1015,6 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>  			fep->speed = phy_dev->speed;
>  			status_change = 1;
>  		}
> -
Unnecessary whitespace change.

>  		/* if any of the above changed restart the FEC */
>  		if (status_change)
>  			fec_restart(ndev, phy_dev->duplex);
> @@ -1007,11 +1026,10 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>  		}
>  	}
>  
> -spin_unlock:
> -	spin_unlock_irqrestore(&fep->hw_lock, flags);
> -
You are eliminating all users of the hw_lock, so please remove it
altogether. Eliminate it from the fec_enet_private struct and the init
in fec_enet_init().

> +exit:
>  	if (status_change)
>  		phy_print_status(phy_dev);
> +
>  }
>  
>  static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
> @@ -1882,6 +1900,7 @@ fec_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto failed_register;
>  
> +	INIT_DELAYED_WORK(&fep->delay_work, fec_enet_work);
>  	return 0;
>  
>  failed_register:
> @@ -1918,6 +1937,7 @@ fec_drv_remove(struct platform_device *pdev)
>  	struct resource *r;
>  	int i;
>  
> +	cancel_delayed_work_sync(&fep->delay_work);
>  	unregister_netdev(ndev);
>  	fec_enet_mii_remove(fep);
>  	del_timer_sync(&fep->time_keep);
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index eb43729..a367b21 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -260,7 +260,8 @@ struct fec_enet_private {
>  	int hwts_rx_en;
>  	int hwts_tx_en;
>  	struct timer_list time_keep;
> -
> +	struct delayed_work delay_work;
> +	int timeout;
I suspect you are going to add more variables like this in the future if
you are using the workqueue more extensively. This is a massive
pollution of the fec_enet_private struct. Please make this a bitfield
with a proper define for the timeout, so we can reuse one variable for
different tasks, or even split this out into it's own struct for the
delayed tasks.

>  };
>  
>  void fec_ptp_init(struct net_device *ndev, struct platform_device *pdev);

-- 
Pengutronix e.K.                           | Lucas Stach                 |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[Frank Li]

2013/5/6 Lucas Stach <l.stach@pengutronix.de>:
> Hi Frank,
>
> Am Donnerstag, den 02.05.2013, 08:55 +0800 schrieb Frank Li:
>> reproduce steps
>>  1. flood ping from other machine
>>       ping -f -s 41000 IP
>>  2. run below script
>>     while [ 1 ]; do ethtool -s eth0 autoneg off;
>>     sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;
>>
>> You can see oops in one hour.
>>
>> The reason is fec_restart clear BD but NAPI may use it.
>> The solution is disable NAPI and stop xmit when reset BD.
>> disable NAPI may sleep, so fec_restart can't be call in
>> atomic context.
>>
>> Signed-off-by: Frank Li <Frank.Li@freescale.com>
>> ---
>> Change from v1 to v2
>>  * Add netif_tx_lock(ndev) to avoid xmit runing when reset hardware
>> Change from v2 to v3
>>  * Move put real statements after function variable declarations according to David's comments
>>  * Remove lock in adjust_link according to Lucas Stach's comments
>>
>>  drivers/net/ethernet/freescale/fec.c |   42 +++++++++++++++++++++++++---------
>>  drivers/net/ethernet/freescale/fec.h |    3 +-
>>  2 files changed, 33 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/freescale/fec.c b/drivers/net/ethernet/freescale/fec.c
>> index 73195f6..5a9345c 100644
>> --- a/drivers/net/ethernet/freescale/fec.c
>> +++ b/drivers/net/ethernet/freescale/fec.c
>> @@ -407,6 +407,12 @@ fec_restart(struct net_device *ndev, int duplex)
>>       u32 rcntl = OPT_FRAME_SIZE | 0x04;
>>       u32 ecntl = 0x2; /* ETHEREN */
>>
>> +     if (netif_running(ndev)) {
>> +             napi_disable(&fep->napi);
>> +             netif_stop_queue(ndev);
>> +             netif_tx_lock(ndev);
>> +     }
>> +
> You did not address the comment from Ben Hutchings here. To make sure we
> are not triggering the netdev watchdog immediately when calling
> netif_stop_queue() we must call netif_device_detach() when entering the
> fec_restart and netif_device_attach() when leaving.

Accepted.

>
> fec_restart gets called when duplex or phy speed changes, not only in
> response to a link up/down change.

Yes.
>
>>       /* Whack a reset.  We should wait for this. */
>>       writel(1, fep->hwp + FEC_ECNTRL);
>>       udelay(10);
>> @@ -559,6 +565,12 @@ fec_restart(struct net_device *ndev, int duplex)
>>
>>       /* Enable interrupts we wish to service */
>>       writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
>> +
>> +     if (netif_running(ndev)) {
>> +             napi_enable(&fep->napi);
>> +             netif_wake_queue(ndev);
>> +             netif_tx_unlock(ndev);
>> +     }
>>  }
>>
>>  static void
>> @@ -598,8 +610,20 @@ fec_timeout(struct net_device *ndev)
>>
>>       ndev->stats.tx_errors++;
>>
>> -     fec_restart(ndev, fep->full_duplex);
>> -     netif_wake_queue(ndev);
>> +     fep->timeout = 1;
>> +     schedule_delayed_work(&fep->delay_work, msecs_to_jiffies(1));
>> +}
> Okay, I understand you want to reuse this workqueue to do other things
> which might require delayed work so a delay workqueue is fine, but
> really use a delay of 0 here.
>
> schedule_delayed_work() internally calls down to queue_delayed_work_on()
> where the documentation states: "If delay is zero and dwork is idle, it
> will be scheduled for immediate execution.", so this is the right thing
> to do here.

Accepted.

>
>> +
>> +static void fec_enet_work(struct work_struct *work)
>> +{
>> +     struct fec_enet_private *fep =
>> +             container_of(work, struct fec_enet_private, delay_work.work);
>> +
>> +     if (fep->timeout) {
>> +             fep->timeout = 0;
>> +             fec_restart(fep->netdev, fep->full_duplex);
>> +             netif_wake_queue(fep->netdev);
>> +     }
>>  }
>>
>>  static void
>> @@ -970,16 +994,12 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>>  {
>>       struct fec_enet_private *fep = netdev_priv(ndev);
>>       struct phy_device *phy_dev = fep->phy_dev;
>> -     unsigned long flags;
>> -
>>       int status_change = 0;
>>
>> -     spin_lock_irqsave(&fep->hw_lock, flags);
>> -
>>       /* Prevent a state halted on mii error */
>>       if (fep->mii_timeout && phy_dev->state == PHY_HALTED) {
>>               phy_dev->state = PHY_RESUMING;
>> -             goto spin_unlock;
>> +             goto exit;
> If we bail out here there is zero chance that we detect a link change,
> so drop the label and just return here.
>
Accepted

>>       }
>>
>>       if (phy_dev->link) {
>> @@ -995,7 +1015,6 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>>                       fep->speed = phy_dev->speed;
>>                       status_change = 1;
>>               }
>> -
> Unnecessary whitespace change.

Accepted

>
>>               /* if any of the above changed restart the FEC */
>>               if (status_change)
>>                       fec_restart(ndev, phy_dev->duplex);
>> @@ -1007,11 +1026,10 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>>               }
>>       }
>>
>> -spin_unlock:
>> -     spin_unlock_irqrestore(&fep->hw_lock, flags);
>> -
> You are eliminating all users of the hw_lock, so please remove it
> altogether. Eliminate it from the fec_enet_private struct and the init
> in fec_enet_init().

Accepted

>
>> +exit:
>>       if (status_change)
>>               phy_print_status(phy_dev);
>> +
>>  }
>>
>>  static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
>> @@ -1882,6 +1900,7 @@ fec_probe(struct platform_device *pdev)
>>       if (ret)
>>               goto failed_register;
>>
>> +     INIT_DELAYED_WORK(&fep->delay_work, fec_enet_work);
>>       return 0;
>>
>>  failed_register:
>> @@ -1918,6 +1937,7 @@ fec_drv_remove(struct platform_device *pdev)
>>       struct resource *r;
>>       int i;
>>
>> +     cancel_delayed_work_sync(&fep->delay_work);
>>       unregister_netdev(ndev);
>>       fec_enet_mii_remove(fep);
>>       del_timer_sync(&fep->time_keep);
>> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
>> index eb43729..a367b21 100644
>> --- a/drivers/net/ethernet/freescale/fec.h
>> +++ b/drivers/net/ethernet/freescale/fec.h
>> @@ -260,7 +260,8 @@ struct fec_enet_private {
>>       int hwts_rx_en;
>>       int hwts_tx_en;
>>       struct timer_list time_keep;
>> -
>> +     struct delayed_work delay_work;
>> +     int timeout;
> I suspect you are going to add more variables like this in the future if
> you are using the workqueue more extensively. This is a massive
> pollution of the fec_enet_private struct. Please make this a bitfield
> with a proper define for the timeout, so we can reuse one variable for
> different tasks, or even split this out into it's own struct for the
> delayed tasks.

Bit | & is not atomic.
So I prefer use two variable. the real work in delay work is very
simple for future workaround.

>
>>  };
>>
>>  void fec_ptp_init(struct net_device *ndev, struct platform_device *pdev);
>
> --
> Pengutronix e.K.                           | Lucas Stach                 |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
>

Re: [PATCH v3 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

[Lucas Stach]

Am Montag, den 06.05.2013, 17:56 +0800 schrieb Frank Li:
> 2013/5/6 Lucas Stach <l.stach@pengutronix.de>:
> > Hi Frank,
> >
> > Am Donnerstag, den 02.05.2013, 08:55 +0800 schrieb Frank Li:
[...]
> >> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> >> index eb43729..a367b21 100644
> >> --- a/drivers/net/ethernet/freescale/fec.h
> >> +++ b/drivers/net/ethernet/freescale/fec.h
> >> @@ -260,7 +260,8 @@ struct fec_enet_private {
> >>       int hwts_rx_en;
> >>       int hwts_tx_en;
> >>       struct timer_list time_keep;
> >> -
> >> +     struct delayed_work delay_work;
> >> +     int timeout;
> > I suspect you are going to add more variables like this in the future if
> > you are using the workqueue more extensively. This is a massive
> > pollution of the fec_enet_private struct. Please make this a bitfield
> > with a proper define for the timeout, so we can reuse one variable for
> > different tasks, or even split this out into it's own struct for the
> > delayed tasks.
> 
> Bit | & is not atomic.
> So I prefer use two variable. the real work in delay work is very
> simple for future workaround.

Ah yes, that's right. Could you then please change the type of the
variable to bool to make it clear that nothing other than true/false
should go into this?

I would still prefer to group the delayed work related things together
in one struct to make the driver more readable overall. Like this:
struct fec_delayed_work {
	struct delayed_work delay_work;
	bool timeout;
	bool future_workaround;
	bool more_delayed_things;
};
And just include this struct in fec_enet_private.

-- 
Pengutronix e.K.                           | Lucas Stach                 |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |