mlxsw: spectrum: Track buffer sizes in struct mlxsw_sp_hdroom

So far, port buffers were always autoconfigured. When dcbnl_setbuffer
callback is implemented, it will allow the user to change the buffer size
configuration by hand. The sizes therefore need to be a configuration
parameter, not always deduced, and therefore belong to struct
mlxsw_sp_hdroom, where the configuration routine should take them from.

Update mlxsw_sp_port_headroom_set() to update these sizes. Have the
function update the sizes even for the case that a given buffer is not
used.

Additionally, change the loop iteration end to DCBX_MAX_BUFFERS instead of
IEEE_8021QAZ_MAX_TCS. The value is the same, but the semantics differ.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -671,19 +671,28 @@ int mlxsw_sp_port_headroom_set(struct mlxsw_sp_port *mlxsw_sp_port,
 	if (err)
 		return err;
 
-	for (i = 0; i < IEEE_8021QAZ_MAX_TCS; i++) {
+	for (i = 0; i < DCBX_MAX_BUFFERS; i++) {
 		struct mlxsw_sp_hdroom_buf *buf = &hdroom->bufs.buf[i];
 		u16 thres_cells;
 		u16 delay_cells;
 		u16 total_cells;
 
-		if (!mlxsw_sp_hdroom_buf_is_used(hdroom, i))
-			continue;
-
+		if (!mlxsw_sp_hdroom_buf_is_used(hdroom, i)) {
+			thres_cells = 0;
+			delay_cells = 0;
+		} else if (buf->lossy) {
+			thres_cells = mlxsw_sp_pg_buf_threshold_get(mlxsw_sp, hdroom->mtu);
+			delay_cells = 0;
+		} else {
 			thres_cells = mlxsw_sp_pg_buf_threshold_get(mlxsw_sp, hdroom->mtu);
-		thres_cells = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, thres_cells);
 			delay_cells = mlxsw_sp_hdroom_buf_delay_get(mlxsw_sp, hdroom);
+		}
+
+		thres_cells = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, thres_cells);
 		delay_cells = mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, delay_cells);
+
+		buf->thres_cells = thres_cells;
+		buf->size_cells = thres_cells + delay_cells;
 		total_cells = thres_cells + delay_cells;
 
 		taken_headroom_cells += total_cells;

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

@@ -447,6 +447,8 @@ struct mlxsw_sp_hdroom_prio {
 };
 
 struct mlxsw_sp_hdroom_buf {
+	u32 thres_cells;
+	u32 size_cells;
 	bool lossy;
 };