mlx4_core: Get the maximum message size from reported device capabilities

Get the maximum message size from the device capabilities returned
from the QUERY_DEV_CAP firmware command, rather than hard-coding 2 GB.

Signed-off-by: Dotan Barak <dotanb@dev.mellanox.co.il>
Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

diff --git a/drivers/net/mlx4/fw.c b/drivers/net/mlx4/fw.c
index d2b0653..c45cbe4 100644
--- a/drivers/net/mlx4/fw.c
+++ b/drivers/net/mlx4/fw.c
@@ -138,6 +138,7 @@
 #define QUERY_DEV_CAP_ACK_DELAY_OFFSET		0x35
 #define QUERY_DEV_CAP_MTU_WIDTH_OFFSET		0x36
 #define QUERY_DEV_CAP_VL_PORT_OFFSET		0x37
+#define QUERY_DEV_CAP_MAX_MSG_SZ_OFFSET		0x38
 #define QUERY_DEV_CAP_MAX_GID_OFFSET		0x3b
 #define QUERY_DEV_CAP_RATE_SUPPORT_OFFSET	0x3c
 #define QUERY_DEV_CAP_MAX_PKEY_OFFSET		0x3f
@@ -220,6 +221,8 @@
 	dev_cap->local_ca_ack_delay = field & 0x1f;
 	MLX4_GET(field, outbox, QUERY_DEV_CAP_VL_PORT_OFFSET);
 	dev_cap->num_ports = field & 0xf;
+	MLX4_GET(field, outbox, QUERY_DEV_CAP_MAX_MSG_SZ_OFFSET);
+	dev_cap->max_msg_sz = 1 << (field & 0x1f);
 	MLX4_GET(stat_rate, outbox, QUERY_DEV_CAP_RATE_SUPPORT_OFFSET);
 	dev_cap->stat_rate_support = stat_rate;
 	MLX4_GET(dev_cap->flags, outbox, QUERY_DEV_CAP_FLAGS_OFFSET);