sfc: Clean up test interrupt handling

Interrupts are normally generated by the event queues, moderated by
timers.  However, they may also be triggered by detection of a 'fatal'
error condition (e.g. memory parity error) or by the host writing to
certain CSR fields as part of a self-test.

The IRQ level/index used for these on Falcon rev B0 and Siena is set
by the KER_INT_LEVE_SEL field and cached by the driver in
efx_nic::fatal_irq_level.  Since this value is also relevant to
self-tests rename the field to just 'irq_level'.

Avoid unnecessary cache traffic by using a per-channel 'last_irq_cpu'
field and only writing to the per-controller field when the interrupt
matches efx_nic::irq_level.  Remove the volatile qualifier and use
ACCESS_ONCE in the places we read these fields.

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

drivers/net/ethernet/sfc/efx.h

@@ -145,6 +145,12 @@ static inline void efx_schedule_channel(struct efx_channel *channel)
 	napi_schedule(&channel->napi_str);
 }
 
+static inline void efx_schedule_channel_irq(struct efx_channel *channel)
+{
+	channel->last_irq_cpu = raw_smp_processor_id();
+	efx_schedule_channel(channel);
+}
+
 extern void efx_link_status_changed(struct efx_nic *efx);
 extern void efx_link_set_advertising(struct efx_nic *efx, u32);
 extern void efx_link_set_wanted_fc(struct efx_nic *efx, u8);

drivers/net/ethernet/sfc/falcon.c

@@ -189,9 +189,9 @@ irqreturn_t falcon_legacy_interrupt_a1(int irq, void *dev_id)
 	falcon_irq_ack_a1(efx);
 
 	if (queues & 1)
-		efx_schedule_channel(efx_get_channel(efx, 0));
+		efx_schedule_channel_irq(efx_get_channel(efx, 0));
 	if (queues & 2)
-		efx_schedule_channel(efx_get_channel(efx, 1));
+		efx_schedule_channel_irq(efx_get_channel(efx, 1));
 	return IRQ_HANDLED;
 }
 /**************************************************************************

drivers/net/ethernet/sfc/net_driver.h

@@ -325,6 +325,7 @@ enum efx_rx_alloc_method {
  * @eventq_mask: Event queue pointer mask
  * @eventq_read_ptr: Event queue read pointer
  * @last_eventq_read_ptr: Last event queue read pointer value.
+ * @last_irq_cpu: Last CPU to handle interrupt for this channel
  * @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
@@ -355,6 +356,7 @@ struct efx_channel {
 	unsigned int eventq_read_ptr;
 	unsigned int last_eventq_read_ptr;
 
+	int last_irq_cpu;
 	unsigned int irq_count;
 	unsigned int irq_mod_score;
 #ifdef CONFIG_RFS_ACCEL
@@ -648,7 +650,7 @@ struct efx_filter_state;
  * @int_error_expire: Time at which error count will be expired
  * @irq_status: Interrupt status buffer
  * @irq_zero_count: Number of legacy IRQs seen with queue flags == 0
- * @fatal_irq_level: IRQ level (bit number) used for serious errors
+ * @irq_level: IRQ level/index for IRQs not triggered by an event queue
  * @mtd_list: List of MTDs attached to the NIC
  * @nic_data: Hardware dependent state
  * @mac_lock: MAC access lock. Protects @port_enabled, @phy_mode,
@@ -679,10 +681,9 @@ struct efx_filter_state;
  * @loopback_selftest: Offline self-test private state
  * @monitor_work: Hardware monitor workitem
  * @biu_lock: BIU (bus interface unit) lock
- * @last_irq_cpu: Last CPU to handle interrupt.
- *	This register is written with the SMP processor ID whenever an
- *	interrupt is handled.  It is used by efx_nic_test_interrupt()
- *	to verify that an interrupt has occurred.
+ * @last_irq_cpu: Last CPU to handle a possible test interrupt.  This
+ *	field is used by efx_test_interrupts() to verify that an
+ *	interrupt has occurred.
  * @n_rx_nodesc_drop_cnt: RX no descriptor drop count
  * @mac_stats: MAC statistics. These include all statistics the MACs
  *	can provide.  Generic code converts these into a standard
@@ -735,7 +736,7 @@ struct efx_nic {
 
 	struct efx_buffer irq_status;
 	unsigned irq_zero_count;
-	unsigned fatal_irq_level;
+	unsigned irq_level;
 
 #ifdef CONFIG_SFC_MTD
 	struct list_head mtd_list;
@@ -779,7 +780,7 @@ struct efx_nic {
 
 	struct delayed_work monitor_work ____cacheline_aligned_in_smp;
 	spinlock_t biu_lock;
-	volatile signed int last_irq_cpu;
+	int last_irq_cpu;
 	unsigned n_rx_nodesc_drop_cnt;
 	struct efx_mac_stats mac_stats;
 	spinlock_t stats_lock;

drivers/net/ethernet/sfc/nic.c

@@ -1311,7 +1311,7 @@ static inline void efx_nic_interrupts(struct efx_nic *efx,
 	efx_oword_t int_en_reg_ker;
 
 	EFX_POPULATE_OWORD_3(int_en_reg_ker,
-			     FRF_AZ_KER_INT_LEVE_SEL, efx->fatal_irq_level,
+			     FRF_AZ_KER_INT_LEVE_SEL, efx->irq_level,
 			     FRF_AZ_KER_INT_KER, force,
 			     FRF_AZ_DRV_INT_EN_KER, enabled);
 	efx_writeo(efx, &int_en_reg_ker, FR_AZ_INT_EN_KER);
@@ -1427,11 +1427,12 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 	efx_readd(efx, &reg, FR_BZ_INT_ISR0);
 	queues = EFX_EXTRACT_DWORD(reg, 0, 31);
 
-	/* Check to see if we have a serious error condition */
-	if (queues & (1U << efx->fatal_irq_level)) {
+	/* Handle non-event-queue sources */
+	if (queues & (1U << efx->irq_level)) {
 		syserr = EFX_OWORD_FIELD(*int_ker, FSF_AZ_NET_IVEC_FATAL_INT);
 		if (unlikely(syserr))
 			return efx_nic_fatal_interrupt(efx);
+		efx->last_irq_cpu = raw_smp_processor_id();
 	}
 
 	if (queues != 0) {
@@ -1441,7 +1442,7 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 		/* Schedule processing of any interrupting queues */
 		efx_for_each_channel(channel, efx) {
 			if (queues & 1)
-				efx_schedule_channel(channel);
+				efx_schedule_channel_irq(channel);
 			queues >>= 1;
 		}
 		result = IRQ_HANDLED;
@@ -1458,18 +1459,16 @@ static irqreturn_t efx_legacy_interrupt(int irq, void *dev_id)
 		efx_for_each_channel(channel, efx) {
 			event = efx_event(channel, channel->eventq_read_ptr);
 			if (efx_event_present(event))
-				efx_schedule_channel(channel);
+				efx_schedule_channel_irq(channel);
 			else
 				efx_nic_eventq_read_ack(channel);
 		}
 	}
 
-	if (result == IRQ_HANDLED) {
-		efx->last_irq_cpu = raw_smp_processor_id();
+	if (result == IRQ_HANDLED)
 		netif_vdbg(efx, intr, efx->net_dev,
 			   "IRQ %d on CPU %d status " EFX_DWORD_FMT "\n",
 			   irq, raw_smp_processor_id(), EFX_DWORD_VAL(reg));
-	}
 
 	return result;
 }
@@ -1488,20 +1487,20 @@ static irqreturn_t efx_msi_interrupt(int irq, void *dev_id)
 	efx_oword_t *int_ker = efx->irq_status.addr;
 	int syserr;
 
-	efx->last_irq_cpu = raw_smp_processor_id();
 	netif_vdbg(efx, intr, efx->net_dev,
 		   "IRQ %d on CPU %d status " EFX_OWORD_FMT "\n",
 		   irq, raw_smp_processor_id(), EFX_OWORD_VAL(*int_ker));
 
-	/* Check to see if we have a serious error condition */
-	if (channel->channel == efx->fatal_irq_level) {
+	/* Handle non-event-queue sources */
+	if (channel->channel == efx->irq_level) {
 		syserr = EFX_OWORD_FIELD(*int_ker, FSF_AZ_NET_IVEC_FATAL_INT);
 		if (unlikely(syserr))
 			return efx_nic_fatal_interrupt(efx);
+		efx->last_irq_cpu = raw_smp_processor_id();
 	}
 
 	/* Schedule processing of the channel */
-	efx_schedule_channel(channel);
+	efx_schedule_channel_irq(channel);
 
 	return IRQ_HANDLED;
 }
@@ -1640,10 +1639,10 @@ void efx_nic_init_common(struct efx_nic *efx)
 
 	if (EFX_WORKAROUND_17213(efx) && !EFX_INT_MODE_USE_MSI(efx))
 		/* Use an interrupt level unused by event queues */
-		efx->fatal_irq_level = 0x1f;
+		efx->irq_level = 0x1f;
 	else
 		/* Use a valid MSI-X vector */
-		efx->fatal_irq_level = 0;
+		efx->irq_level = 0;
 
 	/* Enable all the genuinely fatal interrupts.  (They are still
 	 * masked by the overall interrupt mask, controlled by

drivers/net/ethernet/sfc/selftest.c

@@ -130,6 +130,8 @@ static int efx_test_chip(struct efx_nic *efx, struct efx_self_tests *tests)
 static int efx_test_interrupts(struct efx_nic *efx,
 			       struct efx_self_tests *tests)
 {
+	int cpu;
+
 	netif_dbg(efx, drv, efx->net_dev, "testing interrupts\n");
 	tests->interrupt = -1;
 
@@ -142,16 +144,16 @@ static int efx_test_interrupts(struct efx_nic *efx,
 	/* Wait for arrival of test interrupt. */
 	netif_dbg(efx, drv, efx->net_dev, "waiting for test interrupt\n");
 	schedule_timeout_uninterruptible(HZ / 10);
-	if (efx->last_irq_cpu >= 0)
+	cpu = ACCESS_ONCE(efx->last_irq_cpu);
+	if (cpu >= 0)
 		goto success;
 
 	netif_err(efx, drv, efx->net_dev, "timed out waiting for interrupt\n");
 	return -ETIMEDOUT;
 
  success:
 	netif_dbg(efx, drv, efx->net_dev, "%s test interrupt seen on CPU%d\n",
-		  INT_MODE(efx),
-		efx->last_irq_cpu);
+		  INT_MODE(efx), cpu);
 	tests->interrupt = 1;
 	return 0;
 }
@@ -165,7 +167,7 @@ static int efx_test_eventq_irq(struct efx_channel *channel,
 	bool napi_ran, dma_seen, int_seen;
 
 	read_ptr = channel->eventq_read_ptr;
-	channel->efx->last_irq_cpu = -1;
+	channel->last_irq_cpu = -1;
 	smp_wmb();
 
 	efx_nic_generate_test_event(channel);
@@ -182,7 +184,7 @@ static int efx_test_eventq_irq(struct efx_channel *channel,
 	} else {
 		napi_ran = false;
 		dma_seen = efx_nic_event_present(channel);
-		int_seen = efx->last_irq_cpu >= 0;
+		int_seen = ACCESS_ONCE(channel->last_irq_cpu) >= 0;
 	}
 	napi_enable(&channel->napi_str);
 	efx_nic_eventq_read_ack(channel);