net: macb: Disable PCS auto-negotiation for SGMII fixed-link mode

When using a fixed-link configuration in SGMII mode, it's not really
sensible to have auto-negotiation enabled since the link settings are
fixed by definition. In other configurations, such as an SGMII
connection to a PHY, it should generally be enabled.
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb.h

@@ -159,6 +159,16 @@
 #define GEM_PEFTN		0x01f4 /* PTP Peer Event Frame Tx Ns */
 #define GEM_PEFRSL		0x01f8 /* PTP Peer Event Frame Rx Sec Low */
 #define GEM_PEFRN		0x01fc /* PTP Peer Event Frame Rx Ns */
+#define GEM_PCSCNTRL		0x0200 /* PCS Control */
+#define GEM_PCSSTS		0x0204 /* PCS Status */
+#define GEM_PCSPHYTOPID		0x0208 /* PCS PHY Top ID */
+#define GEM_PCSPHYBOTID		0x020c /* PCS PHY Bottom ID */
+#define GEM_PCSANADV		0x0210 /* PCS AN Advertisement */
+#define GEM_PCSANLPBASE		0x0214 /* PCS AN Link Partner Base */
+#define GEM_PCSANEXP		0x0218 /* PCS AN Expansion */
+#define GEM_PCSANNPTX		0x021c /* PCS AN Next Page TX */
+#define GEM_PCSANNPLP		0x0220 /* PCS AN Next Page LP */
+#define GEM_PCSANEXTSTS		0x023c /* PCS AN Extended Status */
 #define GEM_DCFG1		0x0280 /* Design Config 1 */
 #define GEM_DCFG2		0x0284 /* Design Config 2 */
 #define GEM_DCFG3		0x0288 /* Design Config 3 */
@@ -478,6 +488,10 @@
 #define GEM_HS_MAC_SPEED_OFFSET			0
 #define GEM_HS_MAC_SPEED_SIZE			3
 
+/* Bitfields in PCSCNTRL */
+#define GEM_PCSAUTONEG_OFFSET			12
+#define GEM_PCSAUTONEG_SIZE			1
+
 /* Bitfields in DCFG1. */
 #define GEM_IRQCOR_OFFSET			23
 #define GEM_IRQCOR_SIZE				1

drivers/net/ethernet/cadence/macb_main.c

@@ -694,6 +694,22 @@ static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 	if (old_ncr ^ ncr)
 		macb_or_gem_writel(bp, NCR, ncr);
 
+	/* Disable AN for SGMII fixed link configuration, enable otherwise.
+	 * Must be written after PCSSEL is set in NCFGR,
+	 * otherwise writes will not take effect.
+	 */
+	if (macb_is_gem(bp) && state->interface == PHY_INTERFACE_MODE_SGMII) {
+		u32 pcsctrl, old_pcsctrl;
+
+		old_pcsctrl = gem_readl(bp, PCSCNTRL);
+		if (mode == MLO_AN_FIXED)
+			pcsctrl = old_pcsctrl & ~GEM_BIT(PCSAUTONEG);
+		else
+			pcsctrl = old_pcsctrl | GEM_BIT(PCSAUTONEG);
+		if (old_pcsctrl != pcsctrl)
+			gem_writel(bp, PCSCNTRL, pcsctrl);
+	}
+
 	spin_unlock_irqrestore(&bp->lock, flags);
 }