RE: [PATCH RFC 18/30] net: fec: remove inappropriate calls around fec_restart()

From: Russell King - ARM Linux <redacted> Data: Sunday, June 22, 2014 3:55 PM

To: Duan Fugang-B38611
Cc: linux-arm-kernel@lists.infradead.org; netdev@vger.kernel.org
Subject: Re: [PATCH RFC 18/30] net: fec: remove inappropriate calls around
fec_restart()

On Sun, Jun 22, 2014 at 06:54:28AM +0000, fugang.duan@freescale.com wrote:

quoted

From: Russell King <redacted> Data: Friday, June 20, 2014
8:13 PM

quoted

To: linux-arm-kernel@lists.infradead.org
Cc: Duan Fugang-B38611; netdev@vger.kernel.org
Subject: [PATCH RFC 18/30] net: fec: remove inappropriate calls
around
fec_restart()

This is the second stage to "move calls to quiesce/resume packet
processing out of fec_restart()", where we remove calls which are not
appropriate to the call site.

In the majority of cases, there is no need to detach and reattach the
interface as we are holding the queue xmit lock across the reset.
The exception to that is in fec_resume(), where we are already
detached by the suspend function.  Here, we can remove the call to

detach the interface.

quoted

quoted

We also do not need to stop the transmit queue.  Holding the xmit
lock is enough to ensure that the transmit packet processing is not
running while we perform our task.  However, since fec_restart()
always cleans the rings, we call netif_wake_queue() (or
netif_device_attach() in the case of resume) just before dropping the

xmit lock.  This prevents the watchdog firing.

quoted

quoted

Lastly, always call napi_enable() after the device has been
reattached in the resume path so that we know that the transmit
packet processing is already in an enabled state, so we don't call
netif_wake_queue() while detached.

Signed-off-by: Russell King <redacted>
---
drivers/net/ethernet/freescale/fec_main.c | 26
++++++--------------------
1 file changed, 6 insertions(+), 20 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c

b/drivers/net/ethernet/freescale/fec_main.c
index 4a295b4bfb94..49c154af6da2 100644

--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c

@@ -1058,15 +1058,12 @@ static void fec_enet_work(struct work_struct

*work)

quoted

quoted

		fep->delay_work.timeout = false;
		rtnl_lock();
		if (netif_device_present(ndev) || netif_running(ndev)) {
-			netif_device_detach(ndev);
			napi_disable(&fep->napi);
-			netif_tx_disable(ndev);
			netif_tx_lock_bh(ndev);
			fec_restart(ndev, fep->full_duplex);
-			netif_tx_unlock_bh(ndev);
			netif_wake_queue(ndev);
+			netif_tx_unlock_bh(ndev);
			napi_enable(&fep->napi);
-			netif_device_attach(ndev);
		}
		rtnl_unlock();
	}

@@ -1524,15 +1521,12 @@ static void fec_enet_adjust_link(struct

net_device
*ndev)

		/* if any of the above changed restart the FEC */
		if (status_change) {
-			netif_device_detach(ndev);
			napi_disable(&fep->napi);
-			netif_tx_disable(ndev);
			netif_tx_lock_bh(ndev);
			fec_restart(ndev, phy_dev->duplex);
-			netif_tx_unlock_bh(ndev);
			netif_wake_queue(ndev);
+			netif_tx_unlock_bh(ndev);
			napi_enable(&fep->napi);
-			netif_device_attach(ndev);
		}
	} else {
		if (fep->link) {

@@ -1919,15 +1913,12 @@ static int fec_enet_set_pauseparam(struct

net_device *ndev,
		phy_start_aneg(fep->phy_dev);
	}
	if (netif_running(ndev)) {
-		netif_device_detach(ndev);
		napi_disable(&fep->napi);
-		netif_tx_disable(ndev);
		netif_tx_lock_bh(ndev);
		fec_restart(ndev, fep->full_duplex);
-		netif_tx_unlock_bh(ndev);
		netif_wake_queue(ndev);
+		netif_tx_unlock_bh(ndev);
		napi_enable(&fep->napi);
-		netif_device_attach(ndev);
	}

	return 0;

@@ -2372,15 +2363,12 @@ static int fec_set_features(struct net_device

*netdev,

		if (netif_running(netdev)) {
			fec_stop(netdev);
-			netif_device_detach(netdev);
			napi_disable(&fep->napi);
-			netif_tx_disable(netdev);
			netif_tx_lock_bh(netdev);
			fec_restart(netdev, fep->phy_dev->duplex);
-			netif_tx_unlock_bh(netdev);
			netif_wake_queue(netdev);
+			netif_tx_unlock_bh(netdev);
			napi_enable(&fep->napi);
-			netif_device_attach(netdev);
		}
	}

@@ -2748,15 +2736,13 @@ fec_resume(struct device *dev)

	rtnl_lock();
	if (netif_running(ndev)) {
-		netif_device_detach(ndev);
		napi_disable(&fep->napi);
-		netif_tx_disable(ndev);
		netif_tx_lock_bh(ndev);
		fec_restart(ndev, fep->full_duplex);
+		netif_device_attach(ndev);
		netif_tx_unlock_bh(ndev);
-		netif_wake_queue(ndev);
-		napi_enable(&fep->napi);
		netif_device_attach(ndev);
+		napi_enable(&fep->napi);
		phy_start(fep->phy_dev);
	}
	rtnl_unlock();
--

Patch #17 anc #18 can merge to one patch.

While you can merge various patches together into a single patch, the
question is whether it's the right thing to do.

I kept 17 and 18 separate as 17 is merely moving the calls out without
modification, whereas 18 is changing the functionality.

That makes 17 easy to review - from the reviewer perspective, it's a case
of ensuring that the calls are all placed at the fec_restart() callsite.
Once that's done, then each callsite can be considered on its own merit
for the changes in patch 18.

Understand.

Thanks,
Andy