mlxsw: spectrum_buffers: Support two headroom modes

There are two interfaces to configure ETS: qdiscs and DCB. Historically,
DCB ETS configuration was projected to ingress as well, and configured port
buffers. Qdisc was not.

So as not to break clients that today use DCB ETS and PFC and rely on
getting a reasonable ingress buffer priomap, keep the ETS mirroring in
effect.

Since qdiscs have not done this mirroring historically, it is reasonable
not to introduce it, but rather permit manual ingress configuration through
dcbnl_setbuffer only in the qdisc mode.

This will require a toggle to indicate whether buffer sizes should be
autocomputed or taken from dcbnl_setbuffer, and likewise for priomaps.
Introduce such and initialize it, and guard port buffer size configuration
as appropriate. The toggle is currently left in the DCB position. In a
following patch, qdisc code will switch it.
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.h

@@ -434,18 +434,29 @@ struct mlxsw_sp_hdroom_prio {
 	u8 buf_idx;
 	/* Value of buf_idx deduced from the DCB ETS configuration. */
 	u8 ets_buf_idx;
+	/* Value of buf_idx taken from the dcbnl_setbuffer configuration. */
+	u8 set_buf_idx;
 	bool lossy;
 };
 
 struct mlxsw_sp_hdroom_buf {
 	u32 thres_cells;
 	u32 size_cells;
+	/* Size requirement form dcbnl_setbuffer. */
+	u32 set_size_cells;
 	bool lossy;
 };
 
+enum mlxsw_sp_hdroom_mode {
+	MLXSW_SP_HDROOM_MODE_DCB,
+	MLXSW_SP_HDROOM_MODE_TC,
+};
+
 #define MLXSW_SP_PB_COUNT 10
 
 struct mlxsw_sp_hdroom {
+	enum mlxsw_sp_hdroom_mode mode;
+
 	struct {
 		struct mlxsw_sp_hdroom_prio prio[IEEE_8021Q_MAX_PRIORITIES];
 	} prios;

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

@@ -304,8 +304,16 @@ void mlxsw_sp_hdroom_prios_reset_buf_idx(struct mlxsw_sp_hdroom *hdroom)
 {
 	int prio;
 
-	for (prio = 0; prio < IEEE_8021QAZ_MAX_TCS; prio++)
-		hdroom->prios.prio[prio].buf_idx = hdroom->prios.prio[prio].ets_buf_idx;
+	for (prio = 0; prio < IEEE_8021QAZ_MAX_TCS; prio++) {
+		switch (hdroom->mode) {
+		case MLXSW_SP_HDROOM_MODE_DCB:
+			hdroom->prios.prio[prio].buf_idx = hdroom->prios.prio[prio].ets_buf_idx;
+			break;
+		case MLXSW_SP_HDROOM_MODE_TC:
+			hdroom->prios.prio[prio].buf_idx = hdroom->prios.prio[prio].set_buf_idx;
+			break;
+		}
+	}
 }
 
 void mlxsw_sp_hdroom_bufs_reset_lossiness(struct mlxsw_sp_hdroom *hdroom)
@@ -411,7 +419,14 @@ void mlxsw_sp_hdroom_bufs_reset_sizes(struct mlxsw_sp_port *mlxsw_sp_port,
 		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;
+		if (hdroom->mode == MLXSW_SP_HDROOM_MODE_DCB) {
+			buf->size_cells = thres_cells + delay_cells;
+		} else {
+			/* Do not allow going below the minimum size, even if
+			 * the user requested it.
+			 */
+			buf->size_cells = max(buf->set_size_cells, buf->thres_cells);
+		}
 	}
 }
 
@@ -575,6 +590,7 @@ static int mlxsw_sp_port_headroom_init(struct mlxsw_sp_port *mlxsw_sp_port)
 	int prio;
 
 	hdroom.mtu = mlxsw_sp_port->dev->mtu;
+	hdroom.mode = MLXSW_SP_HDROOM_MODE_DCB;
 	for (prio = 0; prio < IEEE_8021QAZ_MAX_TCS; prio++)
 		hdroom.prios.prio[prio].lossy = true;