[PATCH v5 net-next 14/17] net/sched: taprio: only calculate gate mask per TXQ for igc, stmmac and tsnep

[Vladimir Oltean <vladimir.oltean@nxp.com>]

There are 2 classes of in-tree drivers currently:

- those who act upon struct tc_taprio_sched_entry :: gate_mask as if it
  holds a bit mask of TXQs

- those who act upon the gate_mask as if it holds a bit mask of TCs

When it comes to the standard, IEEE 802.1Q-2018 does say this in the
second paragraph of section 8.6.8.4 Enhancements for scheduled traffic:

| A gate control list associated with each Port contains an ordered list
| of gate operations. Each gate operation changes the transmission gate
| state for the gate associated with each of the Port's traffic class
| queues and allows associated control operations to be scheduled.

In typically obtuse language, it refers to a "traffic class queue"
rather than a "traffic class" or a "queue". But careful reading of
802.1Q clarifies that "traffic class" and "queue" are in fact
synonymous (see 8.6.6 Queuing frames):

| A queue in this context is not necessarily a single FIFO data structure.
| A queue is a record of all frames of a given traffic class awaiting
| transmission on a given Bridge Port. The structure of this record is not
| specified.

i.o.w. their definition of "queue" isn't the Linux TX queue.

The gate_mask really is input into taprio via its UAPI as a mask of
traffic classes, but taprio_sched_to_offload() converts it into a TXQ
mask.

The breakdown of drivers which handle TC_SETUP_QDISC_TAPRIO is:

- hellcreek, felix, sja1105: these are DSA switches, it's not even very
  clear what TXQs correspond to, other than purely software constructs.
  Only the mqprio configuration with 8 TCs and 1 TXQ per TC makes sense.
  So it's fine to convert these to a gate mask per TC.

- enetc: I have the hardware and can confirm that the gate mask is per
  TC, and affects all TXQs (BD rings) configured for that priority.

- igc: in igc_save_qbv_schedule(), the gate_mask is clearly interpreted
  to be per-TXQ.

- tsnep: Gerhard Engleder clarifies that even though this hardware
  supports at most 1 TXQ per TC, the TXQ indices may be different from
  the TC values themselves, and it is the TXQ indices that matter to
  this hardware. So keep it per-TXQ as well.

- stmmac: I have a GMAC datasheet, and in the EST section it does
  specify that the gate events are per TXQ rather than per TC.

- lan966x: again, this is a switch, and while not a DSA one, the way in
  which it implements lan966x_mqprio_add() - by only allowing num_tc ==
  NUM_PRIO_QUEUES (8) - makes it clear to me that TXQs are a purely
  software construct here as well. They seem to map 1:1 with TCs.

- am65_cpsw: from looking at am65_cpsw_est_set_sched_cmds(), I get the
  impression that the fetch_allow variable is treated like a prio_mask.
  I haven't studied this driver's interpretation of the prio_tc_map, but
  that definitely sounds closer to a per-TC gate mask rather than a
  per-TXQ one.

Based on this breakdown, we have 6 drivers with a gate mask per TC and
3 with a gate mask per TXQ. So let's make the gate mask per TXQ the
opt-in and the gate mask per TC the default.

Benefit from the TC_QUERY_CAPS feature that Jakub suggested we add, and
query the device driver before calling the proper ndo_setup_tc(), and
figure out if it expects one or the other format.

Cc: Horatiu Vultur <horatiu.vultur@microchip.com>
Cc: Siddharth Vadapalli <s-vadapalli@ti.com>
Cc: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Kurt Kanzenbach <kurt@linutronix.de> # hellcreek
Reviewed-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
---
v3->v5: none
v2->v3: adjust commit message in light of what Kurt has said
v1->v2:
- rewrite commit message
- also opt in stmmac and tsnep

 drivers/net/ethernet/engleder/tsnep_tc.c      | 21 +++++++++++++++++
 drivers/net/ethernet/intel/igc/igc_main.c     | 23 +++++++++++++++++++
 drivers/net/ethernet/stmicro/stmmac/hwif.h    |  5 ++++
 .../net/ethernet/stmicro/stmmac/stmmac_main.c |  2 ++
 .../net/ethernet/stmicro/stmmac/stmmac_tc.c   | 20 ++++++++++++++++
 include/net/pkt_sched.h                       |  1 +
 net/sched/sch_taprio.c                        | 11 ++++++---
 7 files changed, 80 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/engleder/tsnep_tc.c b/drivers/net/ethernet/engleder/tsnep_tc.c
index c4c6e1357317..d083e6684f12 100644
--- a/drivers/net/ethernet/engleder/tsnep_tc.c
+++ b/drivers/net/ethernet/engleder/tsnep_tc.c
@@ -403,12 +403,33 @@ static int tsnep_taprio(struct tsnep_adapter *adapter,
 	return 0;
 }
 
+static int tsnep_tc_query_caps(struct tsnep_adapter *adapter,
+			       struct tc_query_caps_base *base)
+{
+	switch (base->type) {
+	case TC_SETUP_QDISC_TAPRIO: {
+		struct tc_taprio_caps *caps = base->caps;
+
+		if (!adapter->gate_control)
+			return -EOPNOTSUPP;
+
+		caps->gate_mask_per_txq = true;
+
+		return 0;
+	}
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 int tsnep_tc_setup(struct net_device *netdev, enum tc_setup_type type,
 		   void *type_data)
 {
 	struct tsnep_adapter *adapter = netdev_priv(netdev);
 
 	switch (type) {
+	case TC_QUERY_CAPS:
+		return tsnep_tc_query_caps(adapter, type_data);
 	case TC_SETUP_QDISC_TAPRIO:
 		return tsnep_taprio(adapter, type_data);
 	default:
diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index e86b15efaeb8..cce1dea51f76 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6205,12 +6205,35 @@ static int igc_tsn_enable_cbs(struct igc_adapter *adapter,
 	return igc_tsn_offload_apply(adapter);
 }
 
+static int igc_tc_query_caps(struct igc_adapter *adapter,
+			     struct tc_query_caps_base *base)
+{
+	struct igc_hw *hw = &adapter->hw;
+
+	switch (base->type) {
+	case TC_SETUP_QDISC_TAPRIO: {
+		struct tc_taprio_caps *caps = base->caps;
+
+		if (hw->mac.type != igc_i225)
+			return -EOPNOTSUPP;
+
+		caps->gate_mask_per_txq = true;
+
+		return 0;
+	}
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static int igc_setup_tc(struct net_device *dev, enum tc_setup_type type,
 			void *type_data)
 {
 	struct igc_adapter *adapter = netdev_priv(dev);
 
 	switch (type) {
+	case TC_QUERY_CAPS:
+		return igc_tc_query_caps(adapter, type_data);
 	case TC_SETUP_QDISC_TAPRIO:
 		return igc_tsn_enable_qbv_scheduling(adapter, type_data);
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/hwif.h b/drivers/net/ethernet/stmicro/stmmac/hwif.h
index 592b4067f9b8..16a7421715cb 100644
--- a/drivers/net/ethernet/stmicro/stmmac/hwif.h
+++ b/drivers/net/ethernet/stmicro/stmmac/hwif.h
@@ -567,6 +567,7 @@ struct tc_cbs_qopt_offload;
 struct flow_cls_offload;
 struct tc_taprio_qopt_offload;
 struct tc_etf_qopt_offload;
+struct tc_query_caps_base;
 
 struct stmmac_tc_ops {
 	int (*init)(struct stmmac_priv *priv);
@@ -580,6 +581,8 @@ struct stmmac_tc_ops {
 			    struct tc_taprio_qopt_offload *qopt);
 	int (*setup_etf)(struct stmmac_priv *priv,
 			 struct tc_etf_qopt_offload *qopt);
+	int (*query_caps)(struct stmmac_priv *priv,
+			  struct tc_query_caps_base *base);
 };
 
 #define stmmac_tc_init(__priv, __args...) \
@@ -594,6 +597,8 @@ struct stmmac_tc_ops {
 	stmmac_do_callback(__priv, tc, setup_taprio, __args)
 #define stmmac_tc_setup_etf(__priv, __args...) \
 	stmmac_do_callback(__priv, tc, setup_etf, __args)
+#define stmmac_tc_query_caps(__priv, __args...) \
+	stmmac_do_callback(__priv, tc, query_caps, __args)
 
 struct stmmac_counters;
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b7e5af58ab75..17a7ea1cb961 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5991,6 +5991,8 @@ static int stmmac_setup_tc(struct net_device *ndev, enum tc_setup_type type,
 	struct stmmac_priv *priv = netdev_priv(ndev);
 
 	switch (type) {
+	case TC_QUERY_CAPS:
+		return stmmac_tc_query_caps(priv, priv, type_data);
 	case TC_SETUP_BLOCK:
 		return flow_block_cb_setup_simple(type_data,
 						  &stmmac_block_cb_list,
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
index 2cfb18cef1d4..9d55226479b4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c
@@ -1107,6 +1107,25 @@ static int tc_setup_etf(struct stmmac_priv *priv,
 	return 0;
 }
 
+static int tc_query_caps(struct stmmac_priv *priv,
+			 struct tc_query_caps_base *base)
+{
+	switch (base->type) {
+	case TC_SETUP_QDISC_TAPRIO: {
+		struct tc_taprio_caps *caps = base->caps;
+
+		if (!priv->dma_cap.estsel)
+			return -EOPNOTSUPP;
+
+		caps->gate_mask_per_txq = true;
+
+		return 0;
+	}
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 const struct stmmac_tc_ops dwmac510_tc_ops = {
 	.init = tc_init,
 	.setup_cls_u32 = tc_setup_cls_u32,
@@ -1114,4 +1133,5 @@ const struct stmmac_tc_ops dwmac510_tc_ops = {
 	.setup_cls = tc_setup_cls,
 	.setup_taprio = tc_setup_taprio,
 	.setup_etf = tc_setup_etf,
+	.query_caps = tc_query_caps,
 };
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index ace8be520fb0..fd889fc4912b 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -176,6 +176,7 @@ struct tc_mqprio_qopt_offload {
 
 struct tc_taprio_caps {
 	bool supports_queue_max_sdu:1;
+	bool gate_mask_per_txq:1;
 };
 
 struct tc_taprio_sched_entry {
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index aba8a16842c1..1c95785932b9 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1170,7 +1170,8 @@ static u32 tc_map_to_queue_mask(struct net_device *dev, u32 tc_mask)
 
 static void taprio_sched_to_offload(struct net_device *dev,
 				    struct sched_gate_list *sched,
-				    struct tc_taprio_qopt_offload *offload)
+				    struct tc_taprio_qopt_offload *offload,
+				    const struct tc_taprio_caps *caps)
 {
 	struct sched_entry *entry;
 	int i = 0;
@@ -1184,7 +1185,11 @@ static void taprio_sched_to_offload(struct net_device *dev,
 
 		e->command = entry->command;
 		e->interval = entry->interval;
-		e->gate_mask = tc_map_to_queue_mask(dev, entry->gate_mask);
+		if (caps->gate_mask_per_txq)
+			e->gate_mask = tc_map_to_queue_mask(dev,
+							    entry->gate_mask);
+		else
+			e->gate_mask = entry->gate_mask;
 
 		i++;
 	}
@@ -1229,7 +1234,7 @@ static int taprio_enable_offload(struct net_device *dev,
 	}
 	offload->enable = 1;
 	mqprio_qopt_reconstruct(dev, &offload->mqprio.qopt);
-	taprio_sched_to_offload(dev, sched, offload);
+	taprio_sched_to_offload(dev, sched, offload, &caps);
 
 	for (tc = 0; tc < TC_MAX_QUEUE; tc++)
 		offload->max_sdu[tc] = q->max_sdu[tc];
-- 
2.34.1