Call efx_set_channels() before efx->type->dimension_resources()

When using the "separate_tx_channels=1" module parameter, the TX queues are
initially numbered starting from the first TX-only channel number (after all the
RX-only channels).  efx_set_channels() renumbers the queues so that they are
indexed from zero.

On EF10, the TX queues need to be relabelled in this way before calling the
dimension_resources NIC type operation, otherwise the TX queue PIO buffers can be
linked to the wrong VIs when using "separate_tx_channels=1".

Added comments to explain UC/WC mappings for PIO buffers
Signed-off-by: NShradha Shah <sshah@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef10.c

@@ -565,10 +565,17 @@ static int efx_ef10_dimension_resources(struct efx_nic *efx)
 	 * several of each (in fact that's the only option if host
 	 * page size is >4K).  So we may allocate some extra VIs just
 	 * for writing PIO buffers through.
+	 *
+	 * The UC mapping contains (min_vis - 1) complete VIs and the
+	 * first half of the next VI.  Then the WC mapping begins with
+	 * the second half of this last VI.
 	 */
 	uc_mem_map_size = PAGE_ALIGN((min_vis - 1) * EFX_VI_PAGE_SIZE +
 				     ER_DZ_TX_PIOBUF);
 	if (nic_data->n_piobufs) {
+		/* pio_write_vi_base rounds down to give the number of complete
+		 * VIs inside the UC mapping.
+		 */
 		pio_write_vi_base = uc_mem_map_size / EFX_VI_PAGE_SIZE;
 		wc_mem_map_size = (PAGE_ALIGN((pio_write_vi_base +
 					       nic_data->n_piobufs) *

drivers/net/ethernet/sfc/efx.c

@@ -1599,6 +1599,8 @@ static int efx_probe_nic(struct efx_nic *efx)
 	if (rc)
 		goto fail1;
 
+	efx_set_channels(efx);
+
 	rc = efx->type->dimension_resources(efx);
 	if (rc)
 		goto fail2;
@@ -1609,7 +1611,6 @@ static int efx_probe_nic(struct efx_nic *efx)
 		efx->rx_indir_table[i] =
 			ethtool_rxfh_indir_default(i, efx->rss_spread);
 
-	efx_set_channels(efx);
 	netif_set_real_num_tx_queues(efx->net_dev, efx->n_tx_channels);
 	netif_set_real_num_rx_queues(efx->net_dev, efx->n_rx_channels);