net/mlx5e: Query global pause state before setting prio2buffer

When the user changes prio2buffer mapping while global pause is
enabled, mlx5 driver incorrectly sets all active buffers
(buffer that has at least one priority mapped) to lossy.

Solution:
If global pause is enabled, set all the active buffers to lossless
in prio2buffer command.
Also, add error message when buffer size is not enough to meet
xoff threshold.

Fixes: 0696d608 ("net/mlx5e: Receive buffer configuration")
Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en/port_buffer.c

@@ -155,8 +155,11 @@ static int update_xoff_threshold(struct mlx5e_port_buffer *port_buffer,
 		}
 
 		if (port_buffer->buffer[i].size <
-		    (xoff + max_mtu + (1 << MLX5E_BUFFER_CELL_SHIFT)))
+		    (xoff + max_mtu + (1 << MLX5E_BUFFER_CELL_SHIFT))) {
+			pr_err("buffer_size[%d]=%d is not enough for lossless buffer\n",
+			       i, port_buffer->buffer[i].size);
 			return -ENOMEM;
+		}
 
 		port_buffer->buffer[i].xoff = port_buffer->buffer[i].size - xoff;
 		port_buffer->buffer[i].xon  =
@@ -232,6 +235,26 @@ static int update_buffer_lossy(unsigned int max_mtu,
 	return 0;
 }
 
+static int fill_pfc_en(struct mlx5_core_dev *mdev, u8 *pfc_en)
+{
+	u32 g_rx_pause, g_tx_pause;
+	int err;
+
+	err = mlx5_query_port_pause(mdev, &g_rx_pause, &g_tx_pause);
+	if (err)
+		return err;
+
+	/* If global pause enabled, set all active buffers to lossless.
+	 * Otherwise, check PFC setting.
+	 */
+	if (g_rx_pause || g_tx_pause)
+		*pfc_en = 0xff;
+	else
+		err = mlx5_query_port_pfc(mdev, pfc_en, NULL);
+
+	return err;
+}
+
 #define MINIMUM_MAX_MTU 9216
 int mlx5e_port_manual_buffer_config(struct mlx5e_priv *priv,
 				    u32 change, unsigned int mtu,
@@ -277,7 +300,7 @@ int mlx5e_port_manual_buffer_config(struct mlx5e_priv *priv,
 
 	if (change & MLX5E_PORT_BUFFER_PRIO2BUFFER) {
 		update_prio2buffer = true;
-		err = mlx5_query_port_pfc(priv->mdev, &curr_pfc_en, NULL);
+		err = fill_pfc_en(priv->mdev, &curr_pfc_en);
 		if (err)
 			return err;