linux-kernel - [PATCH] fix PHY polling system blocking

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Message-ID: <1267396749.20057.62.camel@wall-e>
Date:	Sun, 28 Feb 2010 23:39:09 +0100
From:	Stefani Seibold <stefani@...bold.net>
To:	linux-kernel <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] fix PHY polling system blocking

This patch fix the PHY poller, which can block the whole system. On a
Freescale PPC 834x this result in a delay of 450 us due the slow
communication with the PHY chip.

For PHY chips without interrupts, the status of the ethernet will be
polled every 2 sec. The poll function will read some register of the MII
PHY. The time between the sending the MII_READ_COMMAND and receiving the
result is more the 100 us on a PPC 834x.
   
The patch modifies the poller a lit bit. Only a link status state change
will result in a successive detection of the connection type. The poll
cycle on the other hand will be increased to every seconds.

Together this patch will prevent a blocking of nearly 400 us every two
seconds of the whole system on a PPC 834x.

The patch is against kernel 2.6.33. Please merge it.

Signed-off-by: Stefani Seibold <stefani@...bold.net>
---
 phy.c        |    5 ++---
 phy_device.c |   12 +++++++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

diff -u -N -r -p linux-2.6.33.orig/drivers/net/phy/phy.c linux-2.6.33/drivers/net//phy/phy.c
--- linux-2.6.33.orig/drivers/net/phy/phy.c	2010-02-24 19:52:17.000000000 +0100
+++ linux-2.6.33/drivers/net//phy/phy.c	2010-02-28 22:53:14.725464101 +0100
@@ -871,9 +871,8 @@ void phy_state_machine(struct work_struc
 		case PHY_RUNNING:
 			/* Only register a CHANGE if we are
 			 * polling */
-			if (PHY_POLL == phydev->irq)
-				phydev->state = PHY_CHANGELINK;
-			break;
+			if (PHY_POLL != phydev->irq)
+				break;
 		case PHY_CHANGELINK:
 			err = phy_read_status(phydev);
 
diff -u -N -r -p linux-2.6.33.orig/drivers/net/phy/phy_device.c linux-2.6.33/drivers/net//phy/phy_device.c
--- linux-2.6.33.orig/drivers/net/phy/phy_device.c	2010-02-24 19:52:17.000000000 +0100
+++ linux-2.6.33/drivers/net//phy/phy_device.c	2010-02-28 22:53:14.726464145 +0100
@@ -161,7 +161,7 @@ struct phy_device* phy_device_create(str
 	dev->speed = 0;
 	dev->duplex = -1;
 	dev->pause = dev->asym_pause = 0;
-	dev->link = 1;
+	dev->link = 0;
 	dev->interface = PHY_INTERFACE_MODE_GMII;
 
 	dev->autoneg = AUTONEG_ENABLE;
@@ -694,10 +694,16 @@ int genphy_update_link(struct phy_device
 	if (status < 0)
 		return status;
 
-	if ((status & BMSR_LSTATUS) == 0)
+	if ((status & BMSR_LSTATUS) == 0) {
+		if (phydev->link==0)
+			return 1;
 		phydev->link = 0;
-	else
+	}
+	else {
+		if (phydev->link==1)
+			return 1;
 		phydev->link = 1;
+	}
 
 	return 0;
 }


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