From: Ido Schimmel <idosch@mellanox.com>
Date: Sun, 21 Jun 2020 11:29:17 +0300
Subject: mlxsw: spectrum: Do not rely on machine endianness
Patch-mainline: v5.8-rc3
Git-commit: f3fe412b0a634286a6a3753c3f9ff201e6bec716
References: bsc#1176774

The second commit cited below performed a cast of 'u32 buffsize' to
'(u16 *)' when calling mlxsw_sp_port_headroom_8x_adjust():

mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, (u16 *) &buffsize);

Colin noted that this will behave differently on big endian
architectures compared to little endian architectures.

Fix this by following Colin's suggestion and have the function accept
and return 'u32' instead of passing the current size by reference.

Fixes: da382875c616 ("mlxsw: spectrum: Extend to support Spectrum-3 ASIC")
Fixes: 60833d54d56c ("mlxsw: spectrum: Adjust headroom buffers for 8x ports")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Colin Ian King <colin.king@canonical.com>
Suggested-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum.c         |    4 ++--
 drivers/net/ethernet/mellanox/mlxsw/spectrum.h         |    8 +++-----
 drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c |    2 +-
 drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c    |    2 +-
 4 files changed, 7 insertions(+), 9 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
@@ -978,10 +978,10 @@ int __mlxsw_sp_port_headroom_set(struct
 
 		lossy = !(pfc || pause_en);
 		thres_cells = mlxsw_sp_pg_buf_threshold_get(mlxsw_sp, mtu);
-		mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, &thres_cells);
+		thres_cells = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, thres_cells);
 		delay_cells = mlxsw_sp_pg_buf_delay_get(mlxsw_sp, mtu, delay,
 							pfc, pause_en);
-		mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, &delay_cells);
+		delay_cells = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, delay_cells);
 		total_cells = thres_cells + delay_cells;
 
 		taken_headroom_cells += total_cells;
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum.h
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum.h
@@ -374,17 +374,15 @@ mlxsw_sp_port_vlan_find_by_vid(const str
 	return NULL;
 }
 
-static inline void
+static inline u32
 mlxsw_sp_port_headroom_8x_adjust(const struct mlxsw_sp_port *mlxsw_sp_port,
-				 u16 *p_size)
+				 u32 size_cells)
 {
 	/* Ports with eight lanes use two headroom buffers between which the
 	 * configured headroom size is split. Therefore, multiply the calculated
 	 * headroom size by two.
 	 */
-	if (mlxsw_sp_port->mapping.width != 8)
-		return;
-	*p_size *= 2;
+	return mlxsw_sp_port->mapping.width == 8 ? 2 * size_cells : size_cells;
 }
 
 enum mlxsw_sp_flood_type {
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_buffers.c
@@ -312,7 +312,7 @@ static int mlxsw_sp_port_pb_init(struct
 
 		if (i == MLXSW_SP_PB_UNUSED)
 			continue;
-		mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, &size);
+		size = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, size);
 		mlxsw_reg_pbmc_lossy_buffer_pack(pbmc_pl, i, size);
 	}
 	mlxsw_reg_pbmc_lossy_buffer_pack(pbmc_pl,
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
@@ -782,7 +782,7 @@ mlxsw_sp_span_port_buffer_update(struct
 		speed = 0;
 
 	buffsize = mlxsw_sp_span_buffsize_get(mlxsw_sp, speed, mtu);
-	mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, (u16 *) &buffsize);
+	buffsize = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, buffsize);
 	mlxsw_reg_sbib_pack(sbib_pl, mlxsw_sp_port->local_port, buffsize);
 	return mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(sbib), sbib_pl);
 }