microchip: lan865x: fix missing Timer Increment config for Rev.B0/B1

[ Upstream commit 2cd58fe ]

Fix missing configuration for LAN865x silicon revisions B0 and B1 as per
Microchip Application Note AN1760 (Rev F, June 2024).

The Timer Increment register was not being set, which is required for
accurate timestamping. As per the application note, configure the MAC to
set timestamping at the end of the Start of Frame Delimiter (SFD), and
set the Timer Increment register to 40 ns (corresponding to a 25 MHz
internal clock).

Link: https://www.microchip.com/en-us/application-notes/an1760

Fixes: 5cd2340 ("microchip: lan865x: add driver support for Microchip's LAN865X MAC-PHY")
Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250818060514.52795-3-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: ParthibanI17164

drivers/net/ethernet/microchip/lan865x/lan865x.c

@@ -32,6 +32,10 @@
 /* MAC Specific Addr 1 Top Reg */
 #define LAN865X_REG_MAC_H_SADDR1	0x00010023
 
+/* MAC TSU Timer Increment Register */
+#define LAN865X_REG_MAC_TSU_TIMER_INCR		0x00010077
+#define MAC_TSU_TIMER_INCR_COUNT_NANOSECONDS	0x0028
+
 struct lan865x_priv {
 	struct work_struct multicast_work;
 	struct net_device *netdev;
@@ -346,6 +350,21 @@ static int lan865x_probe(struct spi_device *spi)
 		goto free_netdev;
 	}
 
+	/* LAN865x Rev.B0/B1 configuration parameters from AN1760
+	 * As per the Configuration Application Note AN1760 published in the
+	 * link, https://www.microchip.com/en-us/application-notes/an1760
+	 * Revision F (DS60001760G - June 2024), configure the MAC to set time
+	 * stamping at the end of the Start of Frame Delimiter (SFD) and set the
+	 * Timer Increment reg to 40 ns to be used as a 25 MHz internal clock.
+	 */
+	ret = oa_tc6_write_register(priv->tc6, LAN865X_REG_MAC_TSU_TIMER_INCR,
+				    MAC_TSU_TIMER_INCR_COUNT_NANOSECONDS);
+	if (ret) {
+		dev_err(&spi->dev, "Failed to config TSU Timer Incr reg: %d\n",
+			ret);
+		goto oa_tc6_exit;
+	}
+
 	/* As per the point s3 in the below errata, SPI receive Ethernet frame
 	 * transfer may halt when starting the next frame in the same data block
 	 * (chunk) as the end of a previous frame. The RFA field should be