[PATCH] net/ethernet/freescale: rework quiesce/activate for ucc_geth

[PATCH] net/ethernet/freescale: rework quiesce/activate for ucc_geth

[Valentin Longchamp]

ugeth_quiesce/activate are used to halt the controller when there is a
link change that requires to reconfigure the mac.

The previous implementation called netif_device_detach(). This however
causes the initial activation of the netdevice to fail precisely because
it's detached. For details, see [1].

A possible workaround was the revert of commit
net: linkwatch: add check for netdevice being present to linkwatch_do_dev
However, the check introduced in the above commit is correct and shall be
kept.

The netif_device_detach() is thus replaced with
netif_tx_stop_all_queues() that prevents any tranmission. This allows to
perform mac config change required by the link change, without detaching
the corresponding netdevice and thus not preventing its initial
activation.

[1] https://lists.openwall.net/netdev/2020/01/08/201

Signed-off-by: Valentin Longchamp <valentin@longchamp.me>
Acked-by: Matteo Ghidoni <matteo.ghidoni@ch.abb.com>
---
 drivers/net/ethernet/freescale/ucc_geth.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/freescale/ucc_geth.c b/drivers/net/ethernet/freescale/ucc_geth.c
index 6e5f6dd169b5..552e7554a9f8 100644
--- a/drivers/net/ethernet/freescale/ucc_geth.c
+++ b/drivers/net/ethernet/freescale/ucc_geth.c
@@ -42,6 +42,7 @@
 #include <soc/fsl/qe/ucc.h>
 #include <soc/fsl/qe/ucc_fast.h>
 #include <asm/machdep.h>
+#include <net/sch_generic.h>
 
 #include "ucc_geth.h"
 
@@ -1548,11 +1549,8 @@ static int ugeth_disable(struct ucc_geth_private *ugeth, enum comm_dir mode)
 
 static void ugeth_quiesce(struct ucc_geth_private *ugeth)
 {
-	/* Prevent any further xmits, plus detach the device. */
-	netif_device_detach(ugeth->ndev);
-
-	/* Wait for any current xmits to finish. */
-	netif_tx_disable(ugeth->ndev);
+	/* Prevent any further xmits */
+	netif_tx_stop_all_queues(ugeth->ndev);
 
 	/* Disable the interrupt to avoid NAPI rescheduling. */
 	disable_irq(ugeth->ug_info->uf_info.irq);
@@ -1565,7 +1563,10 @@ static void ugeth_activate(struct ucc_geth_private *ugeth)
 {
 	napi_enable(&ugeth->napi);
 	enable_irq(ugeth->ug_info->uf_info.irq);
-	netif_device_attach(ugeth->ndev);
+
+	/* allow to xmit again  */
+	netif_tx_wake_all_queues(ugeth->ndev);
+	__netdev_watchdog_up(ugeth->ndev);
 }
 
 /* Called every time the controller might need to be made
-- 
2.25.1

Re: [PATCH] net/ethernet/freescale: rework quiesce/activate for ucc_geth

[David Miller]

From: Valentin Longchamp <valentin@longchamp.me>
Date: Wed, 20 May 2020 17:53:50 +0200

> ugeth_quiesce/activate are used to halt the controller when there is a
> link change that requires to reconfigure the mac.
> 
> The previous implementation called netif_device_detach(). This however
> causes the initial activation of the netdevice to fail precisely because
> it's detached. For details, see [1].
> 
> A possible workaround was the revert of commit
> net: linkwatch: add check for netdevice being present to linkwatch_do_dev
> However, the check introduced in the above commit is correct and shall be
> kept.
> 
> The netif_device_detach() is thus replaced with
> netif_tx_stop_all_queues() that prevents any tranmission. This allows to
> perform mac config change required by the link change, without detaching
> the corresponding netdevice and thus not preventing its initial
> activation.
> 
> [1] https://lists.openwall.net/netdev/2020/01/08/201
> 
> Signed-off-by: Valentin Longchamp <valentin@longchamp.me>
> Acked-by: Matteo Ghidoni <matteo.ghidoni@ch.abb.com>

Applied, thanks.

Re: [PATCH] net/ethernet/freescale: rework quiesce/activate for ucc_geth

[Valentin Longchamp]

Le 23.05.2020 à 00:50, David Miller a écrit :
> From: Valentin Longchamp <valentin@longchamp.me>
> Date: Wed, 20 May 2020 17:53:50 +0200
> 
>> ugeth_quiesce/activate are used to halt the controller when there is a
>> link change that requires to reconfigure the mac.
>>
>> The previous implementation called netif_device_detach(). This however
>> causes the initial activation of the netdevice to fail precisely because
>> it's detached. For details, see [1].
>>
>> A possible workaround was the revert of commit
>> net: linkwatch: add check for netdevice being present to linkwatch_do_dev
>> However, the check introduced in the above commit is correct and shall be
>> kept.
>>
>> The netif_device_detach() is thus replaced with
>> netif_tx_stop_all_queues() that prevents any tranmission. This allows to
>> perform mac config change required by the link change, without detaching
>> the corresponding netdevice and thus not preventing its initial
>> activation.
>>
>> [1] https://lists.openwall.net/netdev/2020/01/08/201
>>
>> Signed-off-by: Valentin Longchamp <valentin@longchamp.me>
>> Acked-by: Matteo Ghidoni <matteo.ghidoni@ch.abb.com>
> 
> Applied, thanks.
> 

Thanks David.

May I suggest that this get backported to stable until (including) the 
4.19 stable release ?

As the above mentioned commit, merged for 4.19,
124eee3f6955 net: linkwatch: add check for netdevice being present to 
linkwatch_do_dev
does indeed break the ucc_geth driver, this patch can be considered as a 
bugfix that should be taken into account for stable.