net: airoha: fix ETS QoS stats counter underflow and cross-channel corruption

airoha_qdma_get_tx_ets_stats() has two bugs:
- The hardware counters read via airoha_qdma_rr() are 32-bit values
  but are stored in u64 locals and subtracted from u64 baselines. When
  a 32-bit hardware counter wraps around, the subtraction produces a
  large underflow value passed to _bstats_update().
- The baseline counters (cpu_tx_packets, fwd_tx_packets) are stored as
  single per-device fields, but airoha_qdma_get_tx_ets_stats() is
  called with different channel values (0-3). Each call reads a
  different channel's hardware counter but overwrites the same
  baseline, corrupting the delta computation for other channels.

Fix both by:
- Narrowing the counter locals and baselines to u32 so that 32-bit
  unsigned subtraction handles wrap-around naturally.
- Grouping the baselines into a per-channel qos_stats array so each
  channel tracks its own previous counter value independently.
- Splitting the delta addition into two statements so the first u32
  delta is widened to u64 on assignment and the second is added in
  u64 arithmetic, preventing overflow when both deltas are large.

Fixes: 20bf7d07c9 ("net: airoha: Add sched ETS offload support")
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260725-airoha-ethtool-priv_flags-v12-2-5136a30b2157@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/airoha/airoha_eth.c

@@ -2521,16 +2521,20 @@ static int airoha_qdma_get_tx_ets_stats(struct net_device *netdev, int channel,
 {
 	struct airoha_gdm_dev *dev = netdev_priv(netdev);
 	struct airoha_qdma *qdma = dev->qdma;
+	u32 cpu_tx_packets, fwd_tx_packets;
+	u64 tx_packets;
 
-	u64 cpu_tx_packets = airoha_qdma_rr(qdma, REG_CNTR_VAL(channel << 1));
-	u64 fwd_tx_packets = airoha_qdma_rr(qdma,
-					    REG_CNTR_VAL((channel << 1) + 1));
-	u64 tx_packets = (cpu_tx_packets - dev->cpu_tx_packets) +
-			 (fwd_tx_packets - dev->fwd_tx_packets);
+	cpu_tx_packets = airoha_qdma_rr(qdma, REG_CNTR_VAL(channel << 1));
+	fwd_tx_packets = airoha_qdma_rr(qdma,
+					REG_CNTR_VAL((channel << 1) + 1));
+	tx_packets = (u32)(cpu_tx_packets -
+			   dev->qos_stats[channel].cpu_tx_packets);
+	tx_packets += (u32)(fwd_tx_packets -
+			    dev->qos_stats[channel].fwd_tx_packets);
 
 	_bstats_update(opt->stats.bstats, 0, tx_packets);
-	dev->cpu_tx_packets = cpu_tx_packets;
-	dev->fwd_tx_packets = fwd_tx_packets;
+	dev->qos_stats[channel].cpu_tx_packets = cpu_tx_packets;
+	dev->qos_stats[channel].fwd_tx_packets = fwd_tx_packets;
 
 	return 0;
 }

drivers/net/ethernet/airoha/airoha_eth.h

@@ -580,9 +580,10 @@ struct airoha_gdm_dev {
 	struct airoha_eth *eth;
 
 	DECLARE_BITMAP(qos_sq_bmap, AIROHA_NUM_QOS_CHANNELS);
-	/* qos stats counters */
-	u64 cpu_tx_packets;
-	u64 fwd_tx_packets;
+	struct {
+		u32 cpu_tx_packets;
+		u32 fwd_tx_packets;
+	} qos_stats[AIROHA_NUM_QOS_CHANNELS];
 
 	unsigned long flags;
 	int nbq;