igc: add preemptible queue support in taprio

Changes:
1. Introduce tx_enabled flag to control preemptible queue. tx_enabled
   is set via mmsv module based on multiple factors, including link
   up/down status, to determine if FPE is active or inactive.
2. Add priority field to TXDCTL for express queue to improve data
   fetch performance.
3. Block preemptible queue setup in taprio unless reverse-tsn-txq-prio
   private flag is set. Encourages adoption of standard queue priority
   scheme for new features.
4. Hardware-padded frames from preemptible queues result in incorrect
   mCRC values, as padding bytes are excluded from the computation. Pad
   frames to at least 60 bytes using skb_padto() before transmission to
   ensure the hardware includes padding in the mCRC calculation.

Tested preemption with taprio by:
1. Enable FPE:
   ethtool --set-mm enp1s0 pmac-enabled on tx-enabled on verify-enabled on
2. Enable private flag to reverse TX queue priority:
   ethtool --set-priv-flags enp1s0 reverse-txq-prio on
3. Enable preemptible queue in taprio:
   taprio num_tc 4 map 0 1 2 3 0 0 0 0 0 0 0 0 0 0 0 0 \
   queues 1@0 1@1 1@2 1@3 \
   fp P P P E

Reviewed-by: Aleksandr Loktionov <[email protected]>
Co-developed-by: Chwee-Lin Choong <[email protected]>
Signed-off-by: Chwee-Lin Choong <[email protected]>
Signed-off-by: Faizal Rahim <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Tested-by: Mor Bar-Gabay <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>

1 files changed, 18 insertions, 3 deletions

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 82d53fad6b6a..23cbe02ee238 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -1685,6 +1685,15 @@ done:
 	first->tx_flags = tx_flags;
 	first->protocol = protocol;
 
+	/* For preemptible queue, manually pad the skb so that HW includes
+	 * padding bytes in mCRC calculation
+	 */
+	if (tx_ring->preemptible && skb->len < ETH_ZLEN) {
+		if (skb_padto(skb, ETH_ZLEN))
+			goto out_drop;
+		skb_put(skb, ETH_ZLEN - skb->len);
+	}
+
 	tso = igc_tso(tx_ring, first, launch_time, first_flag, &hdr_len);
 	if (tso < 0)
 		goto out_drop;
@@ -6419,6 +6428,7 @@ static int igc_qbv_clear_schedule(struct igc_adapter *adapter)
 		ring->start_time = 0;
 		ring->end_time = NSEC_PER_SEC;
 		ring->max_sdu = 0;
+		ring->preemptible = false;
 	}
 
 	spin_lock_irqsave(&adapter->qbv_tx_lock, flags);
@@ -6484,9 +6494,12 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 	if (!validate_schedule(adapter, qopt))
 		return -EINVAL;
 
-	/* preemptible isn't supported yet */
-	if (qopt->mqprio.preemptible_tcs)
-		return -EOPNOTSUPP;
+	if (qopt->mqprio.preemptible_tcs &&
+	    !(adapter->flags & IGC_FLAG_TSN_REVERSE_TXQ_PRIO)) {
+		NL_SET_ERR_MSG_MOD(qopt->extack,
+				   "reverse-tsn-txq-prio private flag must be enabled before setting preemptible tc");
+		return -ENODEV;
+	}
 
 	igc_ptp_read(adapter, &now);
 
@@ -6579,6 +6592,8 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 			ring->max_sdu = 0;
 	}
 
+	igc_fpe_save_preempt_queue(adapter, &qopt->mqprio);
+
 	return 0;
 }