[PATCH 1/5] sfc: Pad packets to 33 bytes to prevent TX packet parser lockup

[PATCH 1/5] sfc: Pad packets to 33 bytes to prevent TX packet parser lockup

[Ben Hutchings]

The packet parser used in the TX data path for locating checksum
fields can lose synchronisation with the TX queue manager when
handling packets that look like IPv4 but are too short (17-32 bytes).
Work around this by padding to 33 bytes.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/sfc/tx.c          |    8 ++++++++
 drivers/net/sfc/workarounds.h |    2 ++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/net/sfc/tx.c b/drivers/net/sfc/tx.c
index b1e1907..d6681ed 100644
--- a/drivers/net/sfc/tx.c
+++ b/drivers/net/sfc/tx.c
@@ -162,6 +162,14 @@ static int efx_enqueue_skb(struct efx_tx_queue *tx_queue,
 	/* Get size of the initial fragment */
 	len = skb_headlen(skb);
 
+	/* Pad if necessary */
+	if (EFX_WORKAROUND_15592(efx) && skb->len <= 32) {
+		EFX_BUG_ON_PARANOID(skb->data_len);
+		len = 32 + 1;
+		if (skb_pad(skb, len - skb->len))
+			return NETDEV_TX_OK;
+	}
+
 	fill_level = tx_queue->insert_count - tx_queue->old_read_count;
 	q_space = efx->type->txd_ring_mask - 1 - fill_level;
 
diff --git a/drivers/net/sfc/workarounds.h b/drivers/net/sfc/workarounds.h
index 78de68f..c821c15 100644
--- a/drivers/net/sfc/workarounds.h
+++ b/drivers/net/sfc/workarounds.h
@@ -36,6 +36,8 @@
 #define EFX_WORKAROUND_11482 EFX_WORKAROUND_ALWAYS
 /* Flush events can take a very long time to appear */
 #define EFX_WORKAROUND_11557 EFX_WORKAROUND_ALWAYS
+/* Truncated IPv4 packets can confuse the TX packet parser */
+#define EFX_WORKAROUND_15592 EFX_WORKAROUND_ALWAYS
 
 /* Spurious parity errors in TSORT buffers */
 #define EFX_WORKAROUND_5129 EFX_WORKAROUND_FALCON_A

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[PATCH 2/5] sfc: Work around unreliable legacy interrupt status

[Ben Hutchings]

In rare cases, reading the legacy interrupt status register can
acknowledge an event queue whose attention flag has not yet been set
in the register.  Until we service this event queue it will not
generate any more interrupts.  Therefore, as a secondary check, poll
the next slot in each active event queue whose flag is not set.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/sfc/falcon.c |   26 ++++++++++++++------------
 1 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index 2ae51fd..92ea614 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -1435,6 +1435,7 @@ static irqreturn_t falcon_legacy_interrupt_b0(int irq, void *dev_id)
 {
 	struct efx_nic *efx = dev_id;
 	efx_oword_t *int_ker = efx->irq_status.addr;
+	irqreturn_t result = IRQ_NONE;
 	struct efx_channel *channel;
 	efx_dword_t reg;
 	u32 queues;
@@ -1449,23 +1450,24 @@ static irqreturn_t falcon_legacy_interrupt_b0(int irq, void *dev_id)
 	if (unlikely(syserr))
 		return falcon_fatal_interrupt(efx);
 
-	if (queues == 0)
-		return IRQ_NONE;
-
-	efx->last_irq_cpu = raw_smp_processor_id();
-	EFX_TRACE(efx, "IRQ %d on CPU %d status " EFX_DWORD_FMT "\n",
-		  irq, raw_smp_processor_id(), EFX_DWORD_VAL(reg));
-
 	/* Schedule processing of any interrupting queues */
-	channel = &efx->channel[0];
-	while (queues) {
-		if (queues & 0x01)
+	efx_for_each_channel(channel, efx) {
+		if ((queues & 1) ||
+		    falcon_event_present(
+			    falcon_event(channel, channel->eventq_read_ptr))) {
 			efx_schedule_channel(channel);
-		channel++;
+			result = IRQ_HANDLED;
+		}
 		queues >>= 1;
 	}
 
-	return IRQ_HANDLED;
+	if (result == IRQ_HANDLED) {
+		efx->last_irq_cpu = raw_smp_processor_id();
+		EFX_TRACE(efx, "IRQ %d on CPU %d status " EFX_DWORD_FMT "\n",
+			  irq, raw_smp_processor_id(), EFX_DWORD_VAL(reg));
+	}
+
+	return result;
 }
 

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[PATCH 3/5] sfc: Remove unused private PCI register definitions

[Ben Hutchings]

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/sfc/falcon.c |    7 -------
 1 files changed, 0 insertions(+), 7 deletions(-)

diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index 92ea614..f42fc60 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -155,13 +155,6 @@ MODULE_PARM_DESC(rx_xon_thresh_bytes, "RX fifo XON threshold");
 /* Dummy SRAM size code */
 #define SRM_NB_BSZ_ONCHIP_ONLY (-1)
 
-/* Be nice if these (or equiv.) were in linux/pci_regs.h, but they're not. */
-#define PCI_EXP_DEVCAP_PWR_VAL_LBN	18
-#define PCI_EXP_DEVCAP_PWR_SCL_LBN	26
-#define PCI_EXP_DEVCTL_PAYLOAD_LBN	5
-#define PCI_EXP_LNKSTA_LNK_WID		0x3f0
-#define PCI_EXP_LNKSTA_LNK_WID_LBN	4
-
 #define FALCON_IS_DUAL_FUNC(efx)		\
 	(falcon_rev(efx) < FALCON_REV_B0)
 

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[PATCH 4/5] sfc: Optimise falcon_writel_page_locked() for page > 0

[Ben Hutchings]

The bug this function works around only applies to the first set of
page-mapped registers; other pages can be written without locking.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/sfc/falcon_io.h |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/sfc/falcon_io.h b/drivers/net/sfc/falcon_io.h
index c16da31..8883092 100644
--- a/drivers/net/sfc/falcon_io.h
+++ b/drivers/net/sfc/falcon_io.h
@@ -238,18 +238,21 @@ static inline void falcon_writel_page(struct efx_nic *efx, efx_dword_t *value,
 /* Write dword to Falcon page-mapped register with an extra lock.
  *
  * As for falcon_writel_page(), but for a register that suffers from
- * SFC bug 3181. Take out a lock so the BIU collector cannot be
- * confused. */
+ * SFC bug 3181.  If writing to page 0, take out a lock so the BIU
+ * collector cannot be confused.
+ */
 static inline void falcon_writel_page_locked(struct efx_nic *efx,
 					     efx_dword_t *value,
 					     unsigned int reg,
 					     unsigned int page)
 {
-	unsigned long flags;
+	unsigned long flags = 0;
 
-	spin_lock_irqsave(&efx->biu_lock, flags);
+	if (page == 0)
+		spin_lock_irqsave(&efx->biu_lock, flags);
 	falcon_writel(efx, value, FALCON_PAGED_REG(page, reg));
-	spin_unlock_irqrestore(&efx->biu_lock, flags);
+	if (page == 0)
+		spin_unlock_irqrestore(&efx->biu_lock, flags);
 }
 
 #endif /* EFX_FALCON_IO_H */

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[PATCH 5/5] sfc: Implement adaptive IRQ moderation

[Ben Hutchings]

Calculate a score for each 1000 IRQs:
- TX completions are worth 1 point
- RX completions are worth 4 if merged using LRO or 2 otherwise

Reduce moderation if the score is less than 10000, down to a minimum
of 5 us.  Increase moderation if the score is more than 20000, up to
the specified maximum.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/sfc/efx.c        |   46 ++++++++++++++++++++++++++++++++++++++++-
 drivers/net/sfc/efx.h        |    2 +-
 drivers/net/sfc/ethtool.c    |   19 +++++-----------
 drivers/net/sfc/falcon.c     |   16 ++++++++++----
 drivers/net/sfc/falcon.h     |    2 +
 drivers/net/sfc/net_driver.h |    9 ++++++++
 6 files changed, 73 insertions(+), 21 deletions(-)

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 8fa68d8..6eff9ca 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -133,6 +133,16 @@ static int phy_flash_cfg;
 module_param(phy_flash_cfg, int, 0644);
 MODULE_PARM_DESC(phy_flash_cfg, "Set PHYs into reflash mode initially");
 
+static unsigned irq_adapt_low_thresh = 10000;
+module_param(irq_adapt_low_thresh, uint, 0644);
+MODULE_PARM_DESC(irq_adapt_low_thresh,
+		 "Threshold score for reducing IRQ moderation");
+
+static unsigned irq_adapt_high_thresh = 20000;
+module_param(irq_adapt_high_thresh, uint, 0644);
+MODULE_PARM_DESC(irq_adapt_high_thresh,
+		 "Threshold score for increasing IRQ moderation");
+
 /**************************************************************************
  *
  * Utility functions and prototypes
@@ -223,6 +233,35 @@ static int efx_poll(struct napi_struct *napi, int budget)
 	rx_packets = efx_process_channel(channel, budget);
 
 	if (rx_packets < budget) {
+		struct efx_nic *efx = channel->efx;
+
+		if (channel->used_flags & EFX_USED_BY_RX &&
+		    efx->irq_rx_adaptive &&
+		    unlikely(++channel->irq_count == 1000)) {
+			unsigned old_irq_moderation = channel->irq_moderation;
+
+			if (unlikely(channel->irq_mod_score <
+				     irq_adapt_low_thresh)) {
+				channel->irq_moderation =
+					max_t(int,
+					      channel->irq_moderation -
+					      FALCON_IRQ_MOD_RESOLUTION,
+					      FALCON_IRQ_MOD_RESOLUTION);
+			} else if (unlikely(channel->irq_mod_score >
+					    irq_adapt_high_thresh)) {
+				channel->irq_moderation =
+					min(channel->irq_moderation +
+					    FALCON_IRQ_MOD_RESOLUTION,
+					    efx->irq_rx_moderation);
+			}
+
+			if (channel->irq_moderation != old_irq_moderation)
+				falcon_set_int_moderation(channel);
+
+			channel->irq_count = 0;
+			channel->irq_mod_score = 0;
+		}
+
 		/* There is no race here; although napi_disable() will
 		 * only wait for napi_complete(), this isn't a problem
 		 * since efx_channel_processed() will have no effect if
@@ -991,7 +1030,7 @@ static int efx_probe_nic(struct efx_nic *efx)
 	efx_set_channels(efx);
 
 	/* Initialise the interrupt moderation settings */
-	efx_init_irq_moderation(efx, tx_irq_mod_usec, rx_irq_mod_usec);
+	efx_init_irq_moderation(efx, tx_irq_mod_usec, rx_irq_mod_usec, true);
 
 	return 0;
 }
@@ -1188,7 +1227,8 @@ void efx_flush_queues(struct efx_nic *efx)
  **************************************************************************/
 
 /* Set interrupt moderation parameters */
-void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs, int rx_usecs)
+void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs, int rx_usecs,
+			     bool rx_adaptive)
 {
 	struct efx_tx_queue *tx_queue;
 	struct efx_rx_queue *rx_queue;
@@ -1198,6 +1238,8 @@ void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs, int rx_usecs)
 	efx_for_each_tx_queue(tx_queue, efx)
 		tx_queue->channel->irq_moderation = tx_usecs;
 
+	efx->irq_rx_adaptive = rx_adaptive;
+	efx->irq_rx_moderation = rx_usecs;
 	efx_for_each_rx_queue(rx_queue, efx)
 		rx_queue->channel->irq_moderation = rx_usecs;
 }
diff --git a/drivers/net/sfc/efx.h b/drivers/net/sfc/efx.h
index 8bde1d2..da157aa 100644
--- a/drivers/net/sfc/efx.h
+++ b/drivers/net/sfc/efx.h
@@ -52,7 +52,7 @@ extern void efx_schedule_reset(struct efx_nic *efx, enum reset_type type);
 extern void efx_suspend(struct efx_nic *efx);
 extern void efx_resume(struct efx_nic *efx);
 extern void efx_init_irq_moderation(struct efx_nic *efx, int tx_usecs,
-				    int rx_usecs);
+				    int rx_usecs, bool rx_adaptive);
 extern int efx_request_power(struct efx_nic *efx, int mw, const char *name);
 extern void efx_hex_dump(const u8 *, unsigned int, const char *);
 
diff --git a/drivers/net/sfc/ethtool.c b/drivers/net/sfc/ethtool.c
index 589d132..64309f4 100644
--- a/drivers/net/sfc/ethtool.c
+++ b/drivers/net/sfc/ethtool.c
@@ -604,7 +604,6 @@ static int efx_ethtool_get_coalesce(struct net_device *net_dev,
 {
 	struct efx_nic *efx = netdev_priv(net_dev);
 	struct efx_tx_queue *tx_queue;
-	struct efx_rx_queue *rx_queue;
 	struct efx_channel *channel;
 
 	memset(coalesce, 0, sizeof(*coalesce));
@@ -622,14 +621,8 @@ static int efx_ethtool_get_coalesce(struct net_device *net_dev,
 		}
 	}
 
-	/* Find lowest IRQ moderation across all used RX queues */
-	coalesce->rx_coalesce_usecs_irq = ~((u32) 0);
-	efx_for_each_rx_queue(rx_queue, efx) {
-		channel = rx_queue->channel;
-		if (channel->irq_moderation < coalesce->rx_coalesce_usecs_irq)
-			coalesce->rx_coalesce_usecs_irq =
-				channel->irq_moderation;
-	}
+	coalesce->use_adaptive_rx_coalesce = efx->irq_rx_adaptive;
+	coalesce->rx_coalesce_usecs_irq = efx->irq_rx_moderation;
 
 	return 0;
 }
@@ -643,10 +636,9 @@ static int efx_ethtool_set_coalesce(struct net_device *net_dev,
 	struct efx_nic *efx = netdev_priv(net_dev);
 	struct efx_channel *channel;
 	struct efx_tx_queue *tx_queue;
-	unsigned tx_usecs, rx_usecs;
+	unsigned tx_usecs, rx_usecs, adaptive;
 
-	if (coalesce->use_adaptive_rx_coalesce ||
-	    coalesce->use_adaptive_tx_coalesce)
+	if (coalesce->use_adaptive_tx_coalesce)
 		return -EOPNOTSUPP;
 
 	if (coalesce->rx_coalesce_usecs || coalesce->tx_coalesce_usecs) {
@@ -657,6 +649,7 @@ static int efx_ethtool_set_coalesce(struct net_device *net_dev,
 
 	rx_usecs = coalesce->rx_coalesce_usecs_irq;
 	tx_usecs = coalesce->tx_coalesce_usecs_irq;
+	adaptive = coalesce->use_adaptive_rx_coalesce;
 
 	/* If the channel is shared only allow RX parameters to be set */
 	efx_for_each_tx_queue(tx_queue, efx) {
@@ -668,7 +661,7 @@ static int efx_ethtool_set_coalesce(struct net_device *net_dev,
 		}
 	}
 
-	efx_init_irq_moderation(efx, tx_usecs, rx_usecs);
+	efx_init_irq_moderation(efx, tx_usecs, rx_usecs, adaptive);
 
 	/* Reset channel to pick up new moderation value.  Note that
 	 * this may change the value of the irq_moderation field
diff --git a/drivers/net/sfc/falcon.c b/drivers/net/sfc/falcon.c
index f42fc60..23a1b14 100644
--- a/drivers/net/sfc/falcon.c
+++ b/drivers/net/sfc/falcon.c
@@ -729,6 +729,9 @@ static void falcon_handle_tx_event(struct efx_channel *channel,
 		tx_ev_desc_ptr = EFX_QWORD_FIELD(*event, TX_EV_DESC_PTR);
 		tx_ev_q_label = EFX_QWORD_FIELD(*event, TX_EV_Q_LABEL);
 		tx_queue = &efx->tx_queue[tx_ev_q_label];
+		channel->irq_mod_score +=
+			(tx_ev_desc_ptr - tx_queue->read_count) &
+			efx->type->txd_ring_mask;
 		efx_xmit_done(tx_queue, tx_ev_desc_ptr);
 	} else if (EFX_QWORD_FIELD(*event, TX_EV_WQ_FF_FULL)) {
 		/* Rewrite the FIFO write pointer */
@@ -898,6 +901,8 @@ static void falcon_handle_rx_event(struct efx_channel *channel,
 			discard = true;
 	}
 
+	channel->irq_mod_score += 2;
+
 	/* Handle received packet */
 	efx_rx_packet(rx_queue, rx_ev_desc_ptr, rx_ev_byte_cnt,
 		      checksummed, discard);
@@ -1075,14 +1080,15 @@ void falcon_set_int_moderation(struct efx_channel *channel)
 		 * program is based at 0.  So actual interrupt moderation
 		 * achieved is ((x + 1) * res).
 		 */
-		unsigned int res = 5;
-		channel->irq_moderation -= (channel->irq_moderation % res);
-		if (channel->irq_moderation < res)
-			channel->irq_moderation = res;
+		channel->irq_moderation -= (channel->irq_moderation %
+					    FALCON_IRQ_MOD_RESOLUTION);
+		if (channel->irq_moderation < FALCON_IRQ_MOD_RESOLUTION)
+			channel->irq_moderation = FALCON_IRQ_MOD_RESOLUTION;
 		EFX_POPULATE_DWORD_2(timer_cmd,
 				     TIMER_MODE, TIMER_MODE_INT_HLDOFF,
 				     TIMER_VAL,
-				     (channel->irq_moderation / res) - 1);
+				     channel->irq_moderation /
+				     FALCON_IRQ_MOD_RESOLUTION - 1);
 	} else {
 		EFX_POPULATE_DWORD_2(timer_cmd,
 				     TIMER_MODE, TIMER_MODE_DIS,
diff --git a/drivers/net/sfc/falcon.h b/drivers/net/sfc/falcon.h
index 7869c3d..77f2e0d 100644
--- a/drivers/net/sfc/falcon.h
+++ b/drivers/net/sfc/falcon.h
@@ -85,6 +85,8 @@ extern void falcon_set_int_moderation(struct efx_channel *channel);
 extern void falcon_disable_interrupts(struct efx_nic *efx);
 extern void falcon_fini_interrupt(struct efx_nic *efx);
 
+#define FALCON_IRQ_MOD_RESOLUTION 5
+
 /* Global Resources */
 extern int falcon_probe_nic(struct efx_nic *efx);
 extern int falcon_probe_resources(struct efx_nic *efx);
diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index b81fc72..e169e5d 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -336,6 +336,8 @@ enum efx_rx_alloc_method {
  * @eventq_read_ptr: Event queue read pointer
  * @last_eventq_read_ptr: Last event queue read pointer value.
  * @eventq_magic: Event queue magic value for driver-generated test events
+ * @irq_count: Number of IRQs since last adaptive moderation decision
+ * @irq_mod_score: IRQ moderation score
  * @rx_alloc_level: Watermark based heuristic counter for pushing descriptors
  *	and diagnostic counters
  * @rx_alloc_push_pages: RX allocation method currently in use for pushing
@@ -364,6 +366,9 @@ struct efx_channel {
 	unsigned int last_eventq_read_ptr;
 	unsigned int eventq_magic;
 
+	unsigned int irq_count;
+	unsigned int irq_mod_score;
+
 	int rx_alloc_level;
 	int rx_alloc_push_pages;
 
@@ -703,6 +708,8 @@ union efx_multicast_hash {
  * @membase: Memory BAR value
  * @biu_lock: BIU (bus interface unit) lock
  * @interrupt_mode: Interrupt mode
+ * @irq_rx_adaptive: Adaptive IRQ moderation enabled for RX event queues
+ * @irq_rx_moderation: IRQ moderation time for RX event queues
  * @i2c_adap: I2C adapter
  * @board_info: Board-level information
  * @state: Device state flag. Serialised by the rtnl_lock.
@@ -784,6 +791,8 @@ struct efx_nic {
 	void __iomem *membase;
 	spinlock_t biu_lock;
 	enum efx_int_mode interrupt_mode;
+	bool irq_rx_adaptive;
+	unsigned int irq_rx_moderation;
 
 	struct i2c_adapter i2c_adap;
 	struct efx_board board_info;

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH 1/5] sfc: Pad packets to 33 bytes to prevent TX packet parser lockup

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Fri, 20 Mar 2009 23:25:39 +0000

> The packet parser used in the TX data path for locating checksum
> fields can lose synchronisation with the TX queue manager when
> handling packets that look like IPv4 but are too short (17-32 bytes).
> Work around this by padding to 33 bytes.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Applied.

Re: [PATCH 2/5] sfc: Work around unreliable legacy interrupt status

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Fri, 20 Mar 2009 23:26:41 +0000

> In rare cases, reading the legacy interrupt status register can
> acknowledge an event queue whose attention flag has not yet been set
> in the register.  Until we service this event queue it will not
> generate any more interrupts.  Therefore, as a secondary check, poll
> the next slot in each active event queue whose flag is not set.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Applied.

Re: [PATCH 3/5] sfc: Remove unused private PCI register definitions

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Fri, 20 Mar 2009 23:26:55 +0000

> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Applied.

Re: [PATCH 4/5] sfc: Optimise falcon_writel_page_locked() for page > 0

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Fri, 20 Mar 2009 23:27:13 +0000

> The bug this function works around only applies to the first set of
> page-mapped registers; other pages can be written without locking.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Applied.

Re: [PATCH 5/5] sfc: Implement adaptive IRQ moderation

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Fri, 20 Mar 2009 23:30:37 +0000

> Calculate a score for each 1000 IRQs:
> - TX completions are worth 1 point
> - RX completions are worth 4 if merged using LRO or 2 otherwise
> 
> Reduce moderation if the score is less than 10000, down to a minimum
> of 5 us.  Increase moderation if the score is more than 20000, up to
> the specified maximum.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Applied.