sfc: on MC reset, clear PIO buffer linkage in TXQs

commit c0795bf6 upstream.

Otherwise, if we fail to allocate new PIO buffers, our TXQs will try to
use the old ones, which aren't there any more.

Fixes: 183233be "sfc: Allocate and link PIO buffers; map them with write-combining"
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/ethernet/sfc/ef10.c

@@ -451,6 +451,17 @@ static int efx_ef10_link_piobufs(struct efx_nic *efx)
 	return rc;
 }
 
+static void efx_ef10_forget_old_piobufs(struct efx_nic *efx)
+{
+	struct efx_channel *channel;
+	struct efx_tx_queue *tx_queue;
+
+	/* All our existing PIO buffers went away */
+	efx_for_each_channel(channel, efx)
+		efx_for_each_channel_tx_queue(tx_queue, channel)
+			tx_queue->piobuf = NULL;
+}
+
 #else /* !EFX_USE_PIO */
 
 static int efx_ef10_alloc_piobufs(struct efx_nic *efx, unsigned int n)
@@ -467,6 +478,10 @@ static void efx_ef10_free_piobufs(struct efx_nic *efx)
 {
 }
 
+static void efx_ef10_forget_old_piobufs(struct efx_nic *efx)
+{
+}
+
 #endif /* EFX_USE_PIO */
 
 static void efx_ef10_remove(struct efx_nic *efx)
@@ -698,6 +713,7 @@ static void efx_ef10_reset_mc_allocations(struct efx_nic *efx)
 	nic_data->must_realloc_vis = true;
 	nic_data->must_restore_filters = true;
 	nic_data->must_restore_piobufs = true;
+	efx_ef10_forget_old_piobufs(efx);
 	nic_data->rx_rss_context = EFX_EF10_RSS_CONTEXT_INVALID;
 }