[Intel-wired-lan] [PATCH iwl-next v1 4/8] igc: assign highest TX queue number as highest priority in mqprio

[Faizal Rahim <faizal.abdul.rahim@linux.intel.com>]

Previously, TX arbitration prioritized queues based on the TC they were
mapped to. A queue mapped to TC 3 had higher priority than one mapped to
TC 0.

To improve code reuse for upcoming patches and align with typical NIC
behavior, this patch updates the logic to prioritize higher queue numbers
when mqprio is used. As a result, queue 0 becomes the lowest priority and
queue 3 becomes the highest.

This patch also introduces igc_tsn_is_tc_to_queue_priority_ordered() to
preserve the original TC-based priority rule and reject configurations
where a higher TC maps to a lower queue offset.

Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 19 ++++++++++++
 drivers/net/ethernet/intel/igc/igc_tsn.c  | 35 ++++++++++++++---------
 2 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 86716fabf6a9..1b58811f8cfa 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6724,6 +6724,19 @@ static void igc_save_mqprio_params(struct igc_adapter *adapter, u8 num_tc,
 		adapter->queue_per_tc[i] = offset[i];
 }
 
+static bool igc_tsn_is_tc_to_queue_priority_ordered(struct tc_mqprio_qopt_offload *mqprio)
+{
+	int i;
+	int num_tc = mqprio->qopt.num_tc;
+
+	for (i = 1; i < num_tc; i++) {
+		if (mqprio->qopt.offset[i - 1] > mqprio->qopt.offset[i])
+			return false;
+	}
+
+	return true;
+}
+
 static int igc_tsn_enable_mqprio(struct igc_adapter *adapter,
 				 struct tc_mqprio_qopt_offload *mqprio)
 {
@@ -6756,6 +6769,12 @@ static int igc_tsn_enable_mqprio(struct igc_adapter *adapter,
 		}
 	}
 
+	if (!igc_tsn_is_tc_to_queue_priority_ordered(mqprio)) {
+		NL_SET_ERR_MSG_MOD(mqprio->extack,
+				   "tc to queue mapping must preserve increasing priority (higher tc → higher queue)");
+		return -EOPNOTSUPP;
+	}
+
 	/* Preemption is not supported yet. */
 	if (mqprio->preemptible_tcs) {
 		NL_SET_ERR_MSG_MOD(mqprio->extack,
diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index e964b11feab1..e1e1c5c89989 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -12,6 +12,13 @@
 #define TX_MIN_FRAG_SIZE		64
 #define TX_MAX_FRAG_SIZE	(TX_MIN_FRAG_SIZE * (MAX_MULTPLIER_TX_MIN_FRAG + 1))
 
+enum tx_queue {
+	TX_QUEUE_0 = 0,
+	TX_QUEUE_1,
+	TX_QUEUE_2,
+	TX_QUEUE_3,
+};
+
 DEFINE_STATIC_KEY_FALSE(igc_fpe_enabled);
 
 static int igc_fpe_init_smd_frame(struct igc_ring *ring,
@@ -236,7 +243,7 @@ bool igc_tsn_is_taprio_activated_by_user(struct igc_adapter *adapter)
 		adapter->taprio_offload_enable;
 }
 
-static void igc_tsn_tx_arb(struct igc_adapter *adapter, u16 *queue_per_tc)
+static void igc_tsn_tx_arb(struct igc_adapter *adapter, bool reverse_prio)
 {
 	struct igc_hw *hw = &adapter->hw;
 	u32 txarb;
@@ -248,10 +255,17 @@ static void igc_tsn_tx_arb(struct igc_adapter *adapter, u16 *queue_per_tc)
 		   IGC_TXARB_TXQ_PRIO_2_MASK |
 		   IGC_TXARB_TXQ_PRIO_3_MASK);
 
-	txarb |= IGC_TXARB_TXQ_PRIO_0(queue_per_tc[3]);
-	txarb |= IGC_TXARB_TXQ_PRIO_1(queue_per_tc[2]);
-	txarb |= IGC_TXARB_TXQ_PRIO_2(queue_per_tc[1]);
-	txarb |= IGC_TXARB_TXQ_PRIO_3(queue_per_tc[0]);
+	if (reverse_prio) {
+		txarb |= IGC_TXARB_TXQ_PRIO_0(TX_QUEUE_3);
+		txarb |= IGC_TXARB_TXQ_PRIO_1(TX_QUEUE_2);
+		txarb |= IGC_TXARB_TXQ_PRIO_2(TX_QUEUE_1);
+		txarb |= IGC_TXARB_TXQ_PRIO_3(TX_QUEUE_0);
+	} else {
+		txarb |= IGC_TXARB_TXQ_PRIO_0(TX_QUEUE_0);
+		txarb |= IGC_TXARB_TXQ_PRIO_1(TX_QUEUE_1);
+		txarb |= IGC_TXARB_TXQ_PRIO_2(TX_QUEUE_2);
+		txarb |= IGC_TXARB_TXQ_PRIO_3(TX_QUEUE_3);
+	}
 
 	wr32(IGC_TXARB, txarb);
 }
@@ -282,7 +296,6 @@ static void igc_tsn_set_rxpbsize(struct igc_adapter *adapter, u32 rxpbs_exp_bmc_
  */
 static int igc_tsn_disable_offload(struct igc_adapter *adapter)
 {
-	u16 queue_per_tc[4] = { 3, 2, 1, 0 };
 	struct igc_hw *hw = &adapter->hw;
 	u32 tqavctrl;
 	int i;
@@ -315,7 +328,7 @@ static int igc_tsn_disable_offload(struct igc_adapter *adapter)
 	/* Restore the default Tx arbitration: Priority 0 has the highest
 	 * priority and is assigned to queue 0 and so on and so forth.
 	 */
-	igc_tsn_tx_arb(adapter, queue_per_tc);
+	igc_tsn_tx_arb(adapter, false);
 
 	adapter->flags &= ~IGC_FLAG_TSN_QBV_ENABLED;
 
@@ -381,12 +394,8 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 	if (igc_is_device_id_i226(hw))
 		igc_tsn_set_retx_qbvfullthreshold(adapter);
 
-	if (adapter->strict_priority_enable) {
-		/* Configure queue priorities according to the user provided
-		 * mapping.
-		 */
-		igc_tsn_tx_arb(adapter, adapter->queue_per_tc);
-	}
+	if (adapter->strict_priority_enable)
+		igc_tsn_tx_arb(adapter, true);
 
 	for (i = 0; i < adapter->num_tx_queues; i++) {
 		struct igc_ring *ring = adapter->tx_ring[i];
-- 
2.34.1