[netdrvr forcedeth] support for irq mitigation

This patch contains support for different modes of interrupt mitigation
of forcedeth. It includes changes based on Jeff's comments. Currently,
the modes are changed through module parameters since ethtool does not
support something similar.
Signed-off-by: Ayaz Abdulla <aabdulla@nvidia.com>

drivers/net/forcedeth.c

@@ -98,6 +98,7 @@
  *	0.43: 10 Aug 2005: Add support for tx checksum.
  *	0.44: 20 Aug 2005: Add support for scatter gather and segmentation.
  *	0.45: 18 Sep 2005: Remove nv_stop/start_rx from every link check
+ *	0.46: 20 Oct 2005: Add irq optimization modes.
  *
  * Known bugs:
  * We suspect that on some hardware no TX done interrupts are generated.
@@ -109,7 +110,7 @@
  * DEV_NEED_TIMERIRQ will not harm you on sane hardware, only generating a few
  * superfluous timer interrupts from the nic.
  */
-#define FORCEDETH_VERSION		"0.45"
+#define FORCEDETH_VERSION		"0.46"
 #define DRV_NAME			"forcedeth"
 
 #include <linux/module.h>
@@ -164,7 +165,8 @@ enum {
 #define NVREG_IRQ_LINK			0x0040
 #define NVREG_IRQ_TX_ERROR		0x0080
 #define NVREG_IRQ_TX1			0x0100
-#define NVREG_IRQMASK_WANTED		0x00df
+#define NVREG_IRQMASK_THROUGHPUT	0x00df
+#define NVREG_IRQMASK_CPU		0x0040
 
 #define NVREG_IRQ_UNKNOWN	(~(NVREG_IRQ_RX_ERROR|NVREG_IRQ_RX|NVREG_IRQ_RX_NOBUF|NVREG_IRQ_TX_ERR| \
 					NVREG_IRQ_TX_OK|NVREG_IRQ_TIMER|NVREG_IRQ_LINK|NVREG_IRQ_TX_ERROR| \
@@ -178,7 +180,8 @@ enum {
  * NVREG_POLL_DEFAULT=97 would result in an interval length of 1 ms
  */
 	NvRegPollingInterval = 0x00c,
-#define NVREG_POLL_DEFAULT	970
+#define NVREG_POLL_DEFAULT_THROUGHPUT	970
+#define NVREG_POLL_DEFAULT_CPU	13
 	NvRegMisc1 = 0x080,
 #define NVREG_MISC1_HD		0x02
 #define NVREG_MISC1_FORCE	0x3b0f3c
@@ -539,6 +542,25 @@ struct fe_priv {
  */
 static int max_interrupt_work = 5;
 
+/*
+ * Optimization can be either throuput mode or cpu mode
+ * 
+ * Throughput Mode: Every tx and rx packet will generate an interrupt.
+ * CPU Mode: Interrupts are controlled by a timer.
+ */
+#define NV_OPTIMIZATION_MODE_THROUGHPUT 0
+#define NV_OPTIMIZATION_MODE_CPU        1
+static int optimization_mode = NV_OPTIMIZATION_MODE_THROUGHPUT;
+
+/*
+ * Poll interval for timer irq
+ *
+ * This interval determines how frequent an interrupt is generated.
+ * The is value is determined by [(time_in_micro_secs * 100) / (2^10)]
+ * Min = 0, and Max = 65535
+ */
+static int poll_interval = -1;
+
 static inline struct fe_priv *get_nvpriv(struct net_device *dev)
 {
 	return netdev_priv(dev);
@@ -1329,6 +1351,7 @@ static void nv_rx_process(struct net_device *dev)
 			if (!(Flags & NV_RX_DESCRIPTORVALID))
 				goto next_pkt;
 
+			if (Flags & NV_RX_ERROR) {
 				if (Flags & NV_RX_MISSEDFRAME) {
 					np->stats.rx_missed_errors++;
 					np->stats.rx_errors++;
@@ -1361,10 +1384,12 @@ static void nv_rx_process(struct net_device *dev)
 						len--;
 					}
 				}
+			}
 		} else {
 			if (!(Flags & NV_RX2_DESCRIPTORVALID))
 				goto next_pkt;
 
+			if (Flags & NV_RX2_ERROR) {
 				if (Flags & (NV_RX2_ERROR1|NV_RX2_ERROR2|NV_RX2_ERROR3)) {
 					np->stats.rx_errors++;
 					goto next_pkt;
@@ -1392,6 +1417,7 @@ static void nv_rx_process(struct net_device *dev)
 						len--;
 					}
 				}
+			}
 			Flags &= NV_RX2_CHECKSUMMASK;
 			if (Flags == NV_RX2_CHECKSUMOK1 ||
 					Flags == NV_RX2_CHECKSUMOK2 ||
@@ -1809,13 +1835,10 @@ static irqreturn_t nv_nic_irq(int foo, void *data, struct pt_regs *regs)
 		if (!(events & np->irqmask))
 			break;
 
-		if (events & (NVREG_IRQ_TX1|NVREG_IRQ_TX_OK|NVREG_IRQ_TX_ERROR|NVREG_IRQ_TX_ERR)) {
 		spin_lock(&np->lock);
 		nv_tx_done(dev);
 		spin_unlock(&np->lock);
-		}
 		
-		if (events & (NVREG_IRQ_RX_ERROR|NVREG_IRQ_RX|NVREG_IRQ_RX_NOBUF)) {
 		nv_rx_process(dev);
 		if (nv_alloc_rx(dev)) {
 			spin_lock(&np->lock);
@@ -1823,7 +1846,6 @@ static irqreturn_t nv_nic_irq(int foo, void *data, struct pt_regs *regs)
 				mod_timer(&np->oom_kick, jiffies + OOM_REFILL);
 			spin_unlock(&np->lock);
 		}
-		}
 		
 		if (events & NVREG_IRQ_LINK) {
 			spin_lock(&np->lock);
@@ -2226,7 +2248,14 @@ static int nv_open(struct net_device *dev)
 	writel(NVREG_RNDSEED_FORCE | (i&NVREG_RNDSEED_MASK), base + NvRegRandomSeed);
 	writel(NVREG_UNKSETUP1_VAL, base + NvRegUnknownSetupReg1);
 	writel(NVREG_UNKSETUP2_VAL, base + NvRegUnknownSetupReg2);
-	writel(NVREG_POLL_DEFAULT, base + NvRegPollingInterval);
+	if (poll_interval == -1) {
+		if (optimization_mode == NV_OPTIMIZATION_MODE_THROUGHPUT)
+			writel(NVREG_POLL_DEFAULT_THROUGHPUT, base + NvRegPollingInterval);
+		else
+			writel(NVREG_POLL_DEFAULT_CPU, base + NvRegPollingInterval);
+	}
+	else
+		writel(poll_interval & 0xFFFF, base + NvRegPollingInterval);
 	writel(NVREG_UNKSETUP6_VAL, base + NvRegUnknownSetupReg6);
 	writel((np->phyaddr << NVREG_ADAPTCTL_PHYSHIFT)|NVREG_ADAPTCTL_PHYVALID|NVREG_ADAPTCTL_RUNNING,
 			base + NvRegAdapterControl);
@@ -2511,7 +2540,11 @@ static int __devinit nv_probe(struct pci_dev *pci_dev, const struct pci_device_i
 	} else {
 		np->tx_flags = NV_TX2_VALID;
 	}
-	np->irqmask = NVREG_IRQMASK_WANTED;
+	if (optimization_mode == NV_OPTIMIZATION_MODE_THROUGHPUT)
+		np->irqmask = NVREG_IRQMASK_THROUGHPUT;
+	else
+		np->irqmask = NVREG_IRQMASK_CPU;
+
 	if (id->driver_data & DEV_NEED_TIMERIRQ)
 		np->irqmask |= NVREG_IRQ_TIMER;
 	if (id->driver_data & DEV_NEED_LINKTIMER) {
@@ -2699,6 +2732,10 @@ static void __exit exit_nic(void)
 
 module_param(max_interrupt_work, int, 0);
 MODULE_PARM_DESC(max_interrupt_work, "forcedeth maximum events handled per interrupt");
+module_param(optimization_mode, int, 0);
+MODULE_PARM_DESC(optimization_mode, "In throughput mode (0), every tx & rx packet will generate an interrupt. In CPU mode (1), interrupts are controlled by a timer.");
+module_param(poll_interval, int, 0);
+MODULE_PARM_DESC(poll_interval, "Interval determines how frequent timer interrupt is generated by [(time_in_micro_secs * 100) / (2^10)]. Min is 0 and Max is 65535.");
 
 MODULE_AUTHOR("Manfred Spraul <manfred@colorfullife.com>");
 MODULE_DESCRIPTION("Reverse Engineered nForce ethernet driver");