From: Andy Gospodarek <gospo@redhat.com>
Date: Thu, 25 Sep 2008 11:38:51 -0400
Subject: [net] e1000: add module param to set tx descriptor power
Message-id: 20080925153847.GB4872@gospo.rdu.redhat.com
O-Subject: [RHEL5.3 PATCH] e1000: add module parameter to set tx descriptor power
Bugzilla: 436966
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: John W. Linville <linville@redhat.com>

Several customers were complaining on RHEL4 that their older 82545/82546
adapters (e1000) were getting constant watchdog timeout messages under
heavy load.  Jesse B. explained to me that there were hardware problems
with those chips that could not be absolutely avoided, but shrinking the
size of the DMA buffers helped avoid the issue.  Intel had been giving
custom drivers to those seeing the problems and that seemed
unreasonable, so I came up with this patch to add a module parameter
called TxDescPower to do the same thing.

The TxDescPower parameter represents the size-order of each transmit
descriptor.  The valid size for descriptors would be 2^6 (64) to 2^12
(4096) bytes each.  One thing to note is that as this value decreases
one may want to consider increasing the TxDescriptors value to maintain
the same amount of buffer memory.

This is not upstream because Jeff didn't think anyone would use it.

This will resolve RHBZ 436966 for RHEL5.

diff --git a/drivers/net/e1000/e1000.h b/drivers/net/e1000/e1000.h
index 18ef6e7..9992a5c 100644
--- a/drivers/net/e1000/e1000.h
+++ b/drivers/net/e1000/e1000.h
@@ -103,6 +103,11 @@ struct e1000_adapter;
 #define E1000_MIN_TXD                       80
 #define E1000_MAX_82544_TXD               4096
 
+#define E1000_DEFAULT_TXD_PWR               12
+#define E1000_MAX_TXD_PWR                   12
+#define E1000_MIN_TXD_PWR                    6
+#define E1000_MAX_82571_TXD_PWR             13
+
 #define E1000_DEFAULT_RXD                  256
 #define E1000_MAX_RXD                      256
 #define E1000_MIN_RXD                       80
@@ -286,6 +291,7 @@ struct e1000_adapter {
 	atomic_t tx_fifo_stall;
 	boolean_t pcix_82544;
 	boolean_t detect_tx_hung;
+	uint32_t tx_desc_pwr;
 
 	/* RX */
 #ifdef CONFIG_E1000_NAPI
diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index 1366a07..6663908 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -2989,9 +2989,6 @@ e1000_tx_csum(struct e1000_adapter *adapter, struct e1000_tx_ring *tx_ring,
 	return FALSE;
 }
 
-#define E1000_MAX_TXD_PWR	12
-#define E1000_MAX_DATA_PER_TXD	(1<<E1000_MAX_TXD_PWR)
-
 static int
 e1000_tx_map(struct e1000_adapter *adapter, struct e1000_tx_ring *tx_ring,
              struct sk_buff *skb, unsigned int first, unsigned int max_per_txd,
@@ -3263,8 +3260,8 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 {
 	struct e1000_adapter *adapter = netdev_priv(netdev);
 	struct e1000_tx_ring *tx_ring;
-	unsigned int first, max_per_txd = E1000_MAX_DATA_PER_TXD;
-	unsigned int max_txd_pwr = E1000_MAX_TXD_PWR;
+	unsigned int max_txd_pwr = adapter->tx_desc_pwr;
+	unsigned int first, max_per_txd = (1 << max_txd_pwr);
 	unsigned int tx_flags = 0;
 	unsigned int len = skb->len - skb->data_len;
 	unsigned long flags;
@@ -3285,11 +3282,6 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 		return NETDEV_TX_OK;
 	}
 
-	/* 82571 and newer doesn't need the workaround that limited descriptor
-	 * length to 4kB */
-	if (adapter->hw.mac_type >= e1000_82571)
-		max_per_txd = 8192;
-
 	mss = skb_shinfo(skb)->gso_size;
 	/* The controller does a simple calculation to
 	 * make sure there is enough room in the FIFO before
diff --git a/drivers/net/e1000/e1000_param.c b/drivers/net/e1000/e1000_param.c
index e6565ce..ebaac5d 100644
--- a/drivers/net/e1000/e1000_param.c
+++ b/drivers/net/e1000/e1000_param.c
@@ -59,6 +59,18 @@
  */
 E1000_PARAM(TxDescriptors, "Number of transmit descriptors");
 
+/* Transmit Descriptor Power
+ *
+ * Valid Range: 6-12
+ * This value represents the size-order of each transmit descriptor.
+ * The valid size for descriptors would be 2^6 (64) to 2^12 (4096) bytes
+ * each.  As this value decreases one may want to consider increasing
+ * the TxDescriptors value to maintain the same amount of frame memory.
+ *
+ * Default Value: 12
+ */
+E1000_PARAM(TxDescPower, "Binary exponential size (2^X) of each transmit descriptor");
+
 /* Receive Descriptor Count
  *
  * Valid Range: 80-256 for 82542 and 82543 gigabit ethernet controllers
@@ -68,6 +80,8 @@ E1000_PARAM(TxDescriptors, "Number of transmit descriptors");
  */
 E1000_PARAM(RxDescriptors, "Number of receive descriptors");
 
+
+
 /* User Specified Speed Override
  *
  * Valid Range: 0, 10, 100, 1000
@@ -314,6 +328,27 @@ e1000_check_options(struct e1000_adapter *adapter)
 		for (i = 0; i < adapter->num_tx_queues; i++)
 			tx_ring[i].count = tx_ring->count;
 	}
+	{ /* Transmit Descriptor Power */
+		struct e1000_option opt = {
+			.type = range_option,
+			.name = "Transmit Descriptor Power",
+			.err  = "using default of "
+			 	__MODULE_STRING(E1000_DEFAULT_TXD_PWR),
+			.def  = adapter->hw.mac_type < e1000_82571 ?
+				E1000_MAX_TXD_PWR : E1000_MAX_82571_TXD_PWR,
+			.arg  = { .r = { .min = E1000_MIN_TXD_PWR }}
+		};
+		opt.arg.r.max = adapter->hw.mac_type < e1000_82571 ?
+			E1000_MAX_TXD_PWR : E1000_MAX_82571_TXD_PWR;
+
+		if (num_TxDescPower > bd) {
+			adapter->tx_desc_pwr = TxDescPower[bd];
+			e1000_validate_option(&adapter->tx_desc_pwr, &opt, adapter);
+		} else {
+			adapter->tx_desc_pwr = opt.def;
+		}
+	}
+
 	{ /* Receive Descriptor Count */
 		struct e1000_option opt = {
 			.type = range_option,