net: ti: icssg-prueth: Fix swapped TX stats for MII interfaces.

[ Upstream commit 919d763 ]

In MII mode, Tx lines are swapped for port0 and port1, which means
Tx port0 receives data from PRU1 and the Tx port1 receives data from
PRU0. This is an expected hardware behavior and reading the Tx stats
needs to be handled accordingly in the driver. Update the driver to
read Tx stats from the PRU1 for port0 and PRU0 for port1.

Fixes: c1e10d5 ("net: ti: icssg-prueth: Add ICSSG Stats")
Signed-off-by: Meghana Malladi <m-malladi@ti.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250603052904.431203-1-m-malladi@ti.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: MeghanaMalladiTI

drivers/net/ethernet/ti/icssg/icssg_stats.c

@@ -29,6 +29,14 @@ void emac_update_hardware_stats(struct prueth_emac *emac)
 	spin_lock(&prueth->stats_lock);
 
 	for (i = 0; i < ARRAY_SIZE(icssg_all_miig_stats); i++) {
+		/* In MII mode TX lines are swapped inside ICSSG, so read Tx stats
+		 * from slice1 for port0 and slice0 for port1 to get accurate Tx
+		 * stats for a given port
+		 */
+		if (emac->phy_if == PHY_INTERFACE_MODE_MII &&
+		    icssg_all_miig_stats[i].offset >= ICSSG_TX_PACKET_OFFSET &&
+		    icssg_all_miig_stats[i].offset <= ICSSG_TX_BYTE_OFFSET)
+			base = stats_base[slice ^ 1];
 		regmap_read(prueth->miig_rt,
 			    base + icssg_all_miig_stats[i].offset,
 			    &val);