mlx4_core: Allow dynamic MTU configuration for IB ports

Set the MTU for IB ports in the driver instead of using the firmware
default of 2KB (the driver defaults to 4KB).  Allow for dynamic mtu
configuration through a new, per-port sysfs entry.

Since there's a dependency between the port MTU and the max number of
HW VLs the port can support, apply a mim/max approach, using a loop
that goes down from the highest possible number of VLs to the lowest,
using the firmware return status to know whether the requested number
of VLs is possible with a given MTU.

For now, as with the dynamic link type change / VPI support, the sysfs
entry to change the mtu is exposed only when NOT running in SR-IOV
mode.  To allow changing the MTU for the master in SR-IOV mode,
primary-function-initiated FLR (Function Level Reset) needs to be
implemented.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/net/ethernet/mellanox/mlx4/main.c

@@ -647,6 +647,99 @@ static ssize_t set_port_type(struct device *dev,
 	return err ? err : count;
 }
 
+enum ibta_mtu {
+	IB_MTU_256  = 1,
+	IB_MTU_512  = 2,
+	IB_MTU_1024 = 3,
+	IB_MTU_2048 = 4,
+	IB_MTU_4096 = 5
+};
+
+static inline int int_to_ibta_mtu(int mtu)
+{
+	switch (mtu) {
+	case 256:  return IB_MTU_256;
+	case 512:  return IB_MTU_512;
+	case 1024: return IB_MTU_1024;
+	case 2048: return IB_MTU_2048;
+	case 4096: return IB_MTU_4096;
+	default: return -1;
+	}
+}
+
+static inline int ibta_mtu_to_int(enum ibta_mtu mtu)
+{
+	switch (mtu) {
+	case IB_MTU_256:  return  256;
+	case IB_MTU_512:  return  512;
+	case IB_MTU_1024: return 1024;
+	case IB_MTU_2048: return 2048;
+	case IB_MTU_4096: return 4096;
+	default: return -1;
+	}
+}
+
+static ssize_t show_port_ib_mtu(struct device *dev,
+			     struct device_attribute *attr,
+			     char *buf)
+{
+	struct mlx4_port_info *info = container_of(attr, struct mlx4_port_info,
+						   port_mtu_attr);
+	struct mlx4_dev *mdev = info->dev;
+
+	if (mdev->caps.port_type[info->port] == MLX4_PORT_TYPE_ETH)
+		mlx4_warn(mdev, "port level mtu is only used for IB ports\n");
+
+	sprintf(buf, "%d\n",
+			ibta_mtu_to_int(mdev->caps.port_ib_mtu[info->port]));
+	return strlen(buf);
+}
+
+static ssize_t set_port_ib_mtu(struct device *dev,
+			     struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct mlx4_port_info *info = container_of(attr, struct mlx4_port_info,
+						   port_mtu_attr);
+	struct mlx4_dev *mdev = info->dev;
+	struct mlx4_priv *priv = mlx4_priv(mdev);
+	int err, port, mtu, ibta_mtu = -1;
+
+	if (mdev->caps.port_type[info->port] == MLX4_PORT_TYPE_ETH) {
+		mlx4_warn(mdev, "port level mtu is only used for IB ports\n");
+		return -EINVAL;
+	}
+
+	err = sscanf(buf, "%d", &mtu);
+	if (err > 0)
+		ibta_mtu = int_to_ibta_mtu(mtu);
+
+	if (err <= 0 || ibta_mtu < 0) {
+		mlx4_err(mdev, "%s is invalid IBTA mtu\n", buf);
+		return -EINVAL;
+	}
+
+	mdev->caps.port_ib_mtu[info->port] = ibta_mtu;
+
+	mlx4_stop_sense(mdev);
+	mutex_lock(&priv->port_mutex);
+	mlx4_unregister_device(mdev);
+	for (port = 1; port <= mdev->caps.num_ports; port++) {
+		mlx4_CLOSE_PORT(mdev, port);
+		err = mlx4_SET_PORT(mdev, port);
+		if (err) {
+			mlx4_err(mdev, "Failed to set port %d, "
+				      "aborting\n", port);
+			goto err_set_port;
+		}
+	}
+	err = mlx4_register_device(mdev);
+err_set_port:
+	mutex_unlock(&priv->port_mutex);
+	mlx4_start_sense(mdev);
+	return err ? err : count;
+}
+
 static int mlx4_load_fw(struct mlx4_dev *dev)
 {
 	struct mlx4_priv *priv = mlx4_priv(dev);
@@ -1362,7 +1455,10 @@ static int mlx4_setup_hca(struct mlx4_dev *dev)
 					  "ib capabilities (%d). Continuing "
 					  "with caps = 0\n", port, err);
 			dev->caps.ib_port_def_cap[port] = ib_port_default_caps;
-
+			if (mlx4_is_mfunc(dev))
+				dev->caps.port_ib_mtu[port] = IB_MTU_2048;
+			else
+				dev->caps.port_ib_mtu[port] = IB_MTU_4096;
 			err = mlx4_check_ext_port_caps(dev, port);
 			if (err)
 				mlx4_warn(dev, "failed to get port %d extended "
@@ -1524,6 +1620,24 @@ static int mlx4_init_port_info(struct mlx4_dev *dev, int port)
 		info->port = -1;
 	}
 
+	sprintf(info->dev_mtu_name, "mlx4_port%d_mtu", port);
+	info->port_mtu_attr.attr.name = info->dev_mtu_name;
+	if (mlx4_is_mfunc(dev))
+		info->port_mtu_attr.attr.mode = S_IRUGO;
+	else {
+		info->port_mtu_attr.attr.mode = S_IRUGO | S_IWUSR;
+		info->port_mtu_attr.store     = set_port_ib_mtu;
+	}
+	info->port_mtu_attr.show      = show_port_ib_mtu;
+	sysfs_attr_init(&info->port_mtu_attr.attr);
+
+	err = device_create_file(&dev->pdev->dev, &info->port_mtu_attr);
+	if (err) {
+		mlx4_err(dev, "Failed to create mtu file for port %d\n", port);
+		device_remove_file(&info->dev->pdev->dev, &info->port_attr);
+		info->port = -1;
+	}
+
 	return err;
 }
 
@@ -1533,6 +1647,7 @@ static void mlx4_cleanup_port_info(struct mlx4_port_info *info)
 		return;
 
 	device_remove_file(&info->dev->pdev->dev, &info->port_attr);
+	device_remove_file(&info->dev->pdev->dev, &info->port_mtu_attr);
 }
 
 static int mlx4_init_steering(struct mlx4_dev *dev)

drivers/net/ethernet/mellanox/mlx4/mlx4.h

@@ -686,6 +686,8 @@ struct mlx4_port_info {
 	char			dev_name[16];
 	struct device_attribute port_attr;
 	enum mlx4_port_type	tmp_type;
+	char			dev_mtu_name[16];
+	struct device_attribute port_mtu_attr;
 	struct mlx4_mac_table	mac_table;
 	struct radix_tree_root	mac_tree;
 	struct mlx4_vlan_table	vlan_table;

drivers/net/ethernet/mellanox/mlx4/port.c

@@ -766,10 +766,18 @@ int mlx4_SET_PORT_wrapper(struct mlx4_dev *dev, int slave,
 				    vhcr->op_modifier, inbox);
 }
 
+/* bit locations for set port command with zero op modifier */
+enum {
+	MLX4_SET_PORT_VL_CAP	 = 4, /* bits 7:4 */
+	MLX4_SET_PORT_MTU_CAP	 = 12, /* bits 15:12 */
+	MLX4_CHANGE_PORT_VL_CAP	 = 21,
+	MLX4_CHANGE_PORT_MTU_CAP = 22,
+};
+
 int mlx4_SET_PORT(struct mlx4_dev *dev, u8 port)
 {
 	struct mlx4_cmd_mailbox *mailbox;
-	int err;
+	int err, vl_cap;
 
 	if (dev->caps.port_type[port] == MLX4_PORT_TYPE_ETH)
 		return 0;
@@ -781,8 +789,19 @@ int mlx4_SET_PORT(struct mlx4_dev *dev, u8 port)
 	memset(mailbox->buf, 0, 256);
 
 	((__be32 *) mailbox->buf)[1] = dev->caps.ib_port_def_cap[port];
-	err = mlx4_cmd(dev, mailbox->dma, port, 0, MLX4_CMD_SET_PORT,
-		       MLX4_CMD_TIME_CLASS_B, MLX4_CMD_WRAPPED);
+
+	/* IB VL CAP enum isn't used by the firmware, just numerical values */
+	for (vl_cap = 8; vl_cap >= 1; vl_cap >>= 1) {
+		((__be32 *) mailbox->buf)[0] = cpu_to_be32(
+			(1 << MLX4_CHANGE_PORT_MTU_CAP) |
+			(1 << MLX4_CHANGE_PORT_VL_CAP)  |
+			(dev->caps.port_ib_mtu[port] << MLX4_SET_PORT_MTU_CAP) |
+			(vl_cap << MLX4_SET_PORT_VL_CAP));
+		err = mlx4_cmd(dev, mailbox->dma, port, 0, MLX4_CMD_SET_PORT,
+				MLX4_CMD_TIME_CLASS_B, MLX4_CMD_WRAPPED);
+		if (err != -ENOMEM)
+			break;
+	}
 
 	mlx4_free_cmd_mailbox(dev, mailbox);
 	return err;

include/linux/mlx4/device.h

@@ -315,6 +315,7 @@ struct mlx4_caps {
 	enum mlx4_port_type	possible_type[MLX4_MAX_PORTS + 1];
 	u32			max_counters;
 	u8			ext_port_cap[MLX4_MAX_PORTS + 1];
+	u8			port_ib_mtu[MLX4_MAX_PORTS + 1];
 };
 
 struct mlx4_buf_list {