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Date:	Wed, 6 Feb 2008 22:08:17 -0800
From:	David Brownell <david-b@...bell.net>
To:	Claudio Lanconelli <lanconelli.claudio@...ar.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [patch 2.6.24-git] net/enc28j60: low power mode

On Wednesday 06 February 2008, Claudio Lanconelli wrote:
> > +		for (;;) {
> > +			tmp = nolock_regb_read(priv, ESTAT);
> > +			if (!(tmp & ESTAT_RXBUSY))
> > +				break;
> > +		}
> >   
> Avoid infinite waiting loops, please.
> Look at enc28j60_phy_read() for example.

Updated patch is appended.

==========	CUT HERE
Keep enc28j60 chips in low-power mode when they're not in use.
At typically 120 mA, these chips run hot even when idle; this
low power mode cuts that power usage by a factor of around 100.

This version provides a generic routine to poll a register until
its masked value equals some value ... e.g. bit set or cleared.
It's basically what the previous wait_phy_ready() did, but this
version is generalized to support the handshaking needed to
enter and exit low power mode.

Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>
---
 drivers/net/enc28j60.c |   70 ++++++++++++++++++++++++++++++++++++++-----------
 1 files changed, 55 insertions(+), 15 deletions(-)

--- a/drivers/net/enc28j60.c
+++ b/drivers/net/enc28j60.c
@@ -400,26 +400,31 @@ enc28j60_packet_write(struct enc28j60_ne
 	mutex_unlock(&priv->lock);
 }
 
-/*
- * Wait until the PHY operation is complete.
- */
-static int wait_phy_ready(struct enc28j60_net *priv)
+static unsigned long msec20_to_jiffies;
+
+static int poll_ready(struct enc28j60_net *priv, u8 reg, u8 mask, u8 val)
 {
-	unsigned long timeout = jiffies + 20 * HZ / 1000;
-	int ret = 1;
+	unsigned long timeout = jiffies + msec20_to_jiffies;
 
 	/* 20 msec timeout read */
-	while (nolock_regb_read(priv, MISTAT) & MISTAT_BUSY) {
+	while ((nolock_regb_read(priv, reg) & mask) != val) {
 		if (time_after(jiffies, timeout)) {
 			if (netif_msg_drv(priv))
-				printk(KERN_DEBUG DRV_NAME
-					": PHY ready timeout!\n");
-			ret = 0;
-			break;
+				dev_dbg(&priv->spi->dev,
+					"reg %02x ready timeout!\n", reg);
+			return -ETIMEDOUT;
 		}
 		cpu_relax();
 	}
-	return ret;
+	return 0;
+}
+
+/*
+ * Wait until the PHY operation is complete.
+ */
+static int wait_phy_ready(struct enc28j60_net *priv)
+{
+	return poll_ready(priv, MISTAT, MISTAT_BUSY, 0) ? 0 : 1;
 }
 
 /*
@@ -594,6 +599,31 @@ static void nolock_txfifo_init(struct en
 	nolock_regw_write(priv, ETXNDL, end);
 }
 
+/*
+ * Low power mode shrinks power consumption about 100x, so we'd like
+ * the chip to be in that mode whenever it's inactive.
+ */
+static void enc28j60_lowpower(struct enc28j60_net *priv, bool is_low)
+{
+	if (netif_msg_drv(priv))
+		dev_dbg(&priv->spi->dev, "%s power...\n",
+				is_low ? "low" : "high");
+
+	mutex_lock(&priv->lock);
+	if (is_low) {
+		nolock_reg_bfclr(priv, ECON1, ECON1_RXEN);
+		poll_ready(priv, ESTAT, ESTAT_RXBUSY, 0);
+		poll_ready(priv, ECON1, ECON1_TXRTS, 0);
+		/* ECON2_VRPS was set during initialization */
+		nolock_reg_bfset(priv, ECON2, ECON2_PWRSV);
+	} else {
+		nolock_reg_bfclr(priv, ECON2, ECON2_PWRSV);
+		poll_ready(priv, ESTAT, ESTAT_CLKRDY, ESTAT_CLKRDY);
+		/* caller sets ECON1_RXEN */
+	}
+	mutex_unlock(&priv->lock);
+}
+
 static int enc28j60_hw_init(struct enc28j60_net *priv)
 {
 	u8 reg;
@@ -612,8 +642,8 @@ static int enc28j60_hw_init(struct enc28
 	priv->tx_retry_count = 0;
 	priv->max_pk_counter = 0;
 	priv->rxfilter = RXFILTER_NORMAL;
-	/* enable address auto increment */
-	nolock_regb_write(priv, ECON2, ECON2_AUTOINC);
+	/* enable address auto increment and voltage regulator powersave */
+	nolock_regb_write(priv, ECON2, ECON2_AUTOINC | ECON2_VRPS);
 
 	nolock_rxfifo_init(priv, RXSTART_INIT, RXEND_INIT);
 	nolock_txfifo_init(priv, TXSTART_INIT, TXEND_INIT);
@@ -690,7 +720,9 @@ static int enc28j60_hw_init(struct enc28
 
 static void enc28j60_hw_enable(struct enc28j60_net *priv)
 {
-	/* enable interrutps */
+	enc28j60_lowpower(priv, false);
+
+	/* enable interrupts */
 	if (netif_msg_hw(priv))
 		printk(KERN_DEBUG DRV_NAME ": %s() enabling interrupts.\n",
 			__FUNCTION__);
@@ -717,6 +749,8 @@ static void enc28j60_hw_disable(struct e
 	nolock_reg_bfclr(priv, ECON1, ECON1_RXEN);
 	priv->hw_enable = false;
 	mutex_unlock(&priv->lock);
+
+	enc28j60_lowpower(priv, true);
 }
 
 static int
@@ -734,6 +768,8 @@ enc28j60_setlink(struct net_device *ndev
 						"hw_reset() failed\n");
 				ret = -EINVAL;
 			}
+			enc28j60_lowpower(priv, true);
+
 		} else {
 			if (netif_msg_link(priv))
 				dev_warn(&ndev->dev,
@@ -1537,6 +1573,8 @@ static int __devinit enc28j60_probe(stru
 	dev->watchdog_timeo = TX_TIMEOUT;
 	SET_ETHTOOL_OPS(dev, &enc28j60_ethtool_ops);
 
+	enc28j60_lowpower(priv, true);
+
 	ret = register_netdev(dev);
 	if (ret) {
 		if (netif_msg_probe(priv))
@@ -1582,6 +1620,8 @@ static struct spi_driver enc28j60_driver
 
 static int __init enc28j60_init(void)
 {
+	msec20_to_jiffies = msecs_to_jiffies(20);
+
 	return spi_register_driver(&enc28j60_driver);
 }
 


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