DM9000: Add mutex to protect access

Add a mutex to serialise access to the chip functions from
entries such as the ethtool and the MII code. This should
reduce the amount of time the spinlock is held to protect
the address register.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/dm9000.c

@@ -102,6 +102,24 @@ static int watchdog = 5000;
 module_param(watchdog, int, 0400);
 MODULE_PARM_DESC(watchdog, "transmit timeout in milliseconds");
 
+/* DM9000 register address locking.
+ *
+ * The DM9000 uses an address register to control where data written
+ * to the data register goes. This means that the address register
+ * must be preserved over interrupts or similar calls.
+ *
+ * During interrupt and other critical calls, a spinlock is used to
+ * protect the system, but the calls themselves save the address
+ * in the address register in case they are interrupting another
+ * access to the device.
+ *
+ * For general accesses a lock is provided so that calls which are
+ * allowed to sleep are serialised so that the address register does
+ * not need to be saved. This lock also serves to serialise access
+ * to the EEPROM and PHY access registers which are shared between
+ * these two devices.
+ */
+
 /* Structure/enum declaration ------------------------------- */
 typedef struct board_info {
 
@@ -132,6 +150,8 @@ typedef struct board_info {
 	struct resource *data_req;
 	struct resource *irq_res;
 
+	struct mutex	 addr_lock;	/* phy and eeprom access lock */
+
 	spinlock_t lock;
 
 	struct mii_if_info mii;
@@ -365,26 +385,16 @@ static void dm9000_get_drvinfo(struct net_device *dev,
 static int dm9000_get_settings(struct net_device *dev, struct ethtool_cmd *cmd)
 {
 	board_info_t *dm = to_dm9000_board(dev);
-	unsigned long flags;
 
-	spin_lock_irqsave(&dm->lock, flags);
 	mii_ethtool_gset(&dm->mii, cmd);
-	spin_lock_irqsave(&dm->lock, flags);
-
 	return 0;
 }
 
 static int dm9000_set_settings(struct net_device *dev, struct ethtool_cmd *cmd)
 {
 	board_info_t *dm = to_dm9000_board(dev);
-	unsigned long flags;
-	int rc;
-
-	spin_lock_irqsave(&dm->lock, flags);
-	rc = mii_ethtool_sset(&dm->mii, cmd);
-	spin_lock_irqsave(&dm->lock, flags);
 
-	return rc;
+	return mii_ethtool_sset(&dm->mii, cmd);
 }
 
 static int dm9000_nway_reset(struct net_device *dev)
@@ -475,6 +485,7 @@ dm9000_probe(struct platform_device *pdev)
 	db->dev = &pdev->dev;
 
 	spin_lock_init(&db->lock);
+	mutex_init(&db->addr_lock);
 
 	if (pdev->num_resources < 2) {
 		ret = -ENODEV;
@@ -997,8 +1008,10 @@ dm9000_rx(struct net_device *dev)
  *  Read a word data from EEPROM
  */
 static void
-dm9000_read_eeprom(board_info_t * db, int offset, unsigned char *to)
+dm9000_read_eeprom(board_info_t *db, int offset, unsigned char *to)
 {
+	mutex_lock(&db->addr_lock);
+
 	iow(db, DM9000_EPAR, offset);
 	iow(db, DM9000_EPCR, EPCR_ERPRR);
 	mdelay(8);		/* according to the datasheet 200us should be enough,
@@ -1007,6 +1020,8 @@ dm9000_read_eeprom(board_info_t * db, int offset, unsigned char *to)
 
 	to[0] = ior(db, DM9000_EPDRL);
 	to[1] = ior(db, DM9000_EPDRH);
+
+	mutex_unlock(&db->addr_lock);
 }
 
 #ifdef DM9000_PROGRAM_EEPROM
@@ -1016,12 +1031,16 @@ dm9000_read_eeprom(board_info_t * db, int offset, unsigned char *to)
 static void
 write_srom_word(board_info_t * db, int offset, u16 val)
 {
+	mutex_lock(&db->addr_lock);
+
 	iow(db, DM9000_EPAR, offset);
 	iow(db, DM9000_EPDRH, ((val >> 8) & 0xff));
 	iow(db, DM9000_EPDRL, (val & 0xff));
 	iow(db, DM9000_EPCR, EPCR_WEP | EPCR_ERPRW);
 	mdelay(8);		/* same shit */
 	iow(db, DM9000_EPCR, 0);
+
+	mutex_unlock(&db->addr_lock);
 }
 
 /*
@@ -1129,6 +1148,8 @@ dm9000_phy_read(struct net_device *dev, int phy_reg_unused, int reg)
 	unsigned int reg_save;
 	int ret;
 
+	mutex_lock(&db->addr_lock);
+
 	spin_lock_irqsave(&db->lock,flags);
 
 	/* Save previous register address */
@@ -1156,6 +1177,7 @@ dm9000_phy_read(struct net_device *dev, int phy_reg_unused, int reg)
 	writeb(reg_save, db->io_addr);
 	spin_unlock_irqrestore(&db->lock,flags);
 
+	mutex_unlock(&db->addr_lock);
 	return ret;
 }
 
@@ -1169,6 +1191,8 @@ dm9000_phy_write(struct net_device *dev, int phyaddr_unused, int reg, int value)
 	unsigned long flags;
 	unsigned long reg_save;
 
+	mutex_lock(&db->addr_lock);
+
 	spin_lock_irqsave(&db->lock,flags);
 
 	/* Save previous register address */
@@ -1184,7 +1208,7 @@ dm9000_phy_write(struct net_device *dev, int phyaddr_unused, int reg, int value)
 	iow(db, DM9000_EPCR, 0xa);	/* Issue phyxcer write command */
 
 	writeb(reg_save, db->io_addr);
-	spin_unlock_irqrestore(&db->lock,flags);
+	spin_unlock_irqrestore(&db->lock, flags);
 
 	dm9000_msleep(db, 1);		/* Wait write complete */
 
@@ -1196,7 +1220,8 @@ dm9000_phy_write(struct net_device *dev, int phyaddr_unused, int reg, int value)
 	/* restore the previous address */
 	writeb(reg_save, db->io_addr);
 
-	spin_unlock_irqrestore(&db->lock,flags);
+	spin_unlock_irqrestore(&db->lock, flags);
+	mutex_unlock(&db->addr_lock);
 }
 
 static int