diff --git a/drivers/net/dsa/sja1105/sja1105.h b/drivers/net/dsa/sja1105/sja1105.h
index dee35ba924ad2..0617d5ccd3ff1 100644
--- a/drivers/net/dsa/sja1105/sja1105.h
+++ b/drivers/net/dsa/sja1105/sja1105.h
@@ -132,6 +132,8 @@ struct sja1105_info {
 	int max_frame_mem;
 	int num_ports;
 	bool multiple_cascade_ports;
+	/* Every {port, TXQ} has its own CBS shaper */
+	bool fixed_cbs_mapping;
 	enum dsa_tag_protocol tag_proto;
 	const struct sja1105_dynamic_table_ops *dyn_ops;
 	const struct sja1105_table_ops *static_ops;
diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index 331bb1c6676ac..a23d980d28f5d 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -2115,11 +2115,36 @@ static void sja1105_bridge_leave(struct dsa_switch *ds, int port,
 }
 
 #define BYTES_PER_KBIT (1000LL / 8)
+/* Port 0 (the uC port) does not have CBS shapers */
+#define SJA1110_FIXED_CBS(port, prio) ((((port) - 1) * SJA1105_NUM_TC) + (prio))
+
+static int sja1105_find_cbs_shaper(struct sja1105_private *priv,
+				   int port, int prio)
+{
+	int i;
+
+	if (priv->info->fixed_cbs_mapping) {
+		i = SJA1110_FIXED_CBS(port, prio);
+		if (i >= 0 && i < priv->info->num_cbs_shapers)
+			return i;
+
+		return -1;
+	}
+
+	for (i = 0; i < priv->info->num_cbs_shapers; i++)
+		if (priv->cbs[i].port == port && priv->cbs[i].prio == prio)
+			return i;
+
+	return -1;
+}
 
 static int sja1105_find_unused_cbs_shaper(struct sja1105_private *priv)
 {
 	int i;
 
+	if (priv->info->fixed_cbs_mapping)
+		return -1;
+
 	for (i = 0; i < priv->info->num_cbs_shapers; i++)
 		if (!priv->cbs[i].idle_slope && !priv->cbs[i].send_slope)
 			return i;
@@ -2150,14 +2175,20 @@ static int sja1105_setup_tc_cbs(struct dsa_switch *ds, int port,
 {
 	struct sja1105_private *priv = ds->priv;
 	struct sja1105_cbs_entry *cbs;
+	s64 port_transmit_rate_kbps;
 	int index;
 
 	if (!offload->enable)
 		return sja1105_delete_cbs_shaper(priv, port, offload->queue);
 
-	index = sja1105_find_unused_cbs_shaper(priv);
-	if (index < 0)
-		return -ENOSPC;
+	/* The user may be replacing an existing shaper */
+	index = sja1105_find_cbs_shaper(priv, port, offload->queue);
+	if (index < 0) {
+		/* That isn't the case - see if we can allocate a new one */
+		index = sja1105_find_unused_cbs_shaper(priv);
+		if (index < 0)
+			return -ENOSPC;
+	}
 
 	cbs = &priv->cbs[index];
 	cbs->port = port;
@@ -2167,9 +2198,17 @@ static int sja1105_setup_tc_cbs(struct dsa_switch *ds, int port,
 	 */
 	cbs->credit_hi = offload->hicredit;
 	cbs->credit_lo = abs(offload->locredit);
-	/* User space is in kbits/sec, hardware in bytes/sec */
-	cbs->idle_slope = offload->idleslope * BYTES_PER_KBIT;
-	cbs->send_slope = abs(offload->sendslope * BYTES_PER_KBIT);
+	/* User space is in kbits/sec, while the hardware in bytes/sec times
+	 * link speed. Since the given offload->sendslope is good only for the
+	 * current link speed anyway, and user space is likely to reprogram it
+	 * when that changes, don't even bother to track the port's link speed,
+	 * but deduce the port transmit rate from idleslope - sendslope.
+	 */
+	port_transmit_rate_kbps = offload->idleslope - offload->sendslope;
+	cbs->idle_slope = div_s64(offload->idleslope * BYTES_PER_KBIT,
+				  port_transmit_rate_kbps);
+	cbs->send_slope = div_s64(abs(offload->sendslope * BYTES_PER_KBIT),
+				  port_transmit_rate_kbps);
 	/* Convert the negative values from 64-bit 2's complement
 	 * to 32-bit 2's complement (for the case of 0x80000000 whose
 	 * negative is still negative).
diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
index 5ce29c8057a41..834b5c1b4db0c 100644
--- a/drivers/net/dsa/sja1105/sja1105_spi.c
+++ b/drivers/net/dsa/sja1105/sja1105_spi.c
@@ -781,6 +781,7 @@ const struct sja1105_info sja1110a_info = {
 	.tag_proto		= DSA_TAG_PROTO_SJA1110,
 	.can_limit_mcast_flood	= true,
 	.multiple_cascade_ports	= true,
+	.fixed_cbs_mapping	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,
@@ -831,6 +832,7 @@ const struct sja1105_info sja1110b_info = {
 	.tag_proto		= DSA_TAG_PROTO_SJA1110,
 	.can_limit_mcast_flood	= true,
 	.multiple_cascade_ports	= true,
+	.fixed_cbs_mapping	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,
@@ -881,6 +883,7 @@ const struct sja1105_info sja1110c_info = {
 	.tag_proto		= DSA_TAG_PROTO_SJA1110,
 	.can_limit_mcast_flood	= true,
 	.multiple_cascade_ports	= true,
+	.fixed_cbs_mapping	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,
@@ -931,6 +934,7 @@ const struct sja1105_info sja1110d_info = {
 	.tag_proto		= DSA_TAG_PROTO_SJA1110,
 	.can_limit_mcast_flood	= true,
 	.multiple_cascade_ports	= true,
+	.fixed_cbs_mapping	= true,
 	.ptp_ts_bits		= 32,
 	.ptpegr_ts_bytes	= 8,
 	.max_frame_mem		= SJA1110_MAX_FRAME_MEMORY,