sfc: MSI-X is the only interrupt mode for EF10 VFs

Add min_interrupt_mode specification per NIC type.
It is a bit confusing because of "highest interrupt mode is less capable".
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef10.c

@@ -6456,6 +6456,7 @@ const struct efx_nic_type efx_hunt_a0_vf_nic_type = {
 	.rx_ts_offset = ES_DZ_RX_PREFIX_TSTAMP_OFST,
 	.can_rx_scatter = true,
 	.always_rx_scatter = true,
+	.min_interrupt_mode = EFX_INT_MODE_MSIX,
 	.max_interrupt_mode = EFX_INT_MODE_MSIX,
 	.timer_period_max = 1 << ERF_DD_EVQ_IND_TIMER_VAL_WIDTH,
 	.offload_features = EF10_OFFLOAD_FEATURES,
@@ -6588,6 +6589,7 @@ const struct efx_nic_type efx_hunt_a0_nic_type = {
 	.can_rx_scatter = true,
 	.always_rx_scatter = true,
 	.option_descriptors = true,
+	.min_interrupt_mode = EFX_INT_MODE_LEGACY,
 	.max_interrupt_mode = EFX_INT_MODE_MSIX,
 	.timer_period_max = 1 << ERF_DD_EVQ_IND_TIMER_VAL_WIDTH,
 	.offload_features = EF10_OFFLOAD_FEATURES,

drivers/net/ethernet/sfc/efx.c

@@ -2935,7 +2935,7 @@ static const struct efx_phy_operations efx_dummy_phy_operations = {
 static int efx_init_struct(struct efx_nic *efx,
 			   struct pci_dev *pci_dev, struct net_device *net_dev)
 {
-	int i;
+	int rc = -ENOMEM, i;
 
 	/* Initialise common structures */
 	INIT_LIST_HEAD(&efx->node);
@@ -2976,8 +2976,15 @@ static int efx_init_struct(struct efx_nic *efx,
 	}
 
 	/* Higher numbered interrupt modes are less capable! */
+	if (WARN_ON_ONCE(efx->type->max_interrupt_mode >
+			 efx->type->min_interrupt_mode)) {
+		rc = -EIO;
+		goto fail;
+	}
 	efx->interrupt_mode = max(efx->type->max_interrupt_mode,
 				  interrupt_mode);
+	efx->interrupt_mode = min(efx->type->min_interrupt_mode,
+				  interrupt_mode);
 
 	/* Would be good to use the net_dev name, but we're too early */
 	snprintf(efx->workqueue_name, sizeof(efx->workqueue_name), "sfc%s",
@@ -2990,7 +2997,7 @@ static int efx_init_struct(struct efx_nic *efx,
 
 fail:
 	efx_fini_struct(efx);
-	return -ENOMEM;
+	return rc;
 }
 
 static void efx_fini_struct(struct efx_nic *efx)

drivers/net/ethernet/sfc/net_driver.h

@@ -1142,8 +1142,10 @@ struct efx_udp_tunnel {
  * @can_rx_scatter: NIC is able to scatter packets to multiple buffers
  * @always_rx_scatter: NIC will always scatter packets to multiple buffers
  * @option_descriptors: NIC supports TX option descriptors
+ * @min_interrupt_mode: Lowest capability interrupt mode supported
+ *	from &enum efx_int_mode.
  * @max_interrupt_mode: Highest capability interrupt mode supported
- *	from &enum efx_init_mode.
+ *	from &enum efx_int_mode.
  * @timer_period_max: Maximum period of interrupt timer (in ticks)
  * @offload_features: net_device feature flags for protocol offload
  *	features implemented in hardware
@@ -1306,6 +1308,7 @@ struct efx_nic_type {
 	bool can_rx_scatter;
 	bool always_rx_scatter;
 	bool option_descriptors;
+	unsigned int min_interrupt_mode;
 	unsigned int max_interrupt_mode;
 	unsigned int timer_period_max;
 	netdev_features_t offload_features;

drivers/net/ethernet/sfc/siena.c

@@ -1069,6 +1069,7 @@ const struct efx_nic_type siena_a0_nic_type = {
 	.rx_buffer_padding = 0,
 	.can_rx_scatter = true,
 	.option_descriptors = false,
+	.min_interrupt_mode = EFX_INT_MODE_LEGACY,
 	.max_interrupt_mode = EFX_INT_MODE_MSIX,
 	.timer_period_max = 1 << FRF_CZ_TC_TIMER_VAL_WIDTH,
 	.offload_features = (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |