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Date:	Sun, 22 Jun 2014 08:55:14 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"fugang.duan@...escale.com" <fugang.duan@...escale.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"netdev@...r.kernel.org" <netdev@...r.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@...escale.com wrote:
> From: Russell King <rmk@....linux.org.uk> Data: Friday, June 20, 2014 8:13 PM
> >To: linux-arm-kernel@...ts.infradead.org
> >Cc: Duan Fugang-B38611; netdev@...r.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.
> >
> >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.
> >
> >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 <rmk+kernel@....linux.org.uk>
> >---
> > 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)
> > 		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.

-- 
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
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