net: macb: fix for suspend-to-mem feature

When suspending the macb, the management port for the MIIM interface was
disabled. When resuming, the PHY (KSZ8081RNB) was no longer responding.
We have to keep the management port enable to fix this issue.

Moreover, to get an up-to-date backup of the NCFGR register, it has to
be done just before suspending the macb.

Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
[claudiu.beznea@microchip.com: conform with latest driver version]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>

Author: ldesroches

drivers/net/ethernet/cadence/macb_main.c

@@ -1884,14 +1884,23 @@ static void macb_reset_hw(struct macb *bp)
 {
 	struct macb_queue *queue;
 	unsigned int q;
+	unsigned long ctrl;
+
+	/*
+	 * Be careful to not disable port management, it seems that some
+	 * PHYs don't like it.
+	 */
+	ctrl = macb_readl(bp, NCR);
 
 	/* Disable RX and TX (XXX: Should we halt the transmission
 	 * more gracefully?)
 	 */
-	macb_writel(bp, NCR, 0);
+	ctrl &= ~(MACB_BIT(RE) | MACB_BIT(TE));
+	macb_writel(bp, NCR, ctrl);
 
 	/* Clear the stats registers (XXX: Update stats first?) */
-	macb_writel(bp, NCR, MACB_BIT(CLRSTAT));
+	ctrl |= MACB_BIT(CLRSTAT);
+	macb_writel(bp, NCR, ctrl);
 
 	/* Clear all status flags */
 	macb_writel(bp, TSR, -1);
@@ -3650,6 +3659,7 @@ static int __maybe_unused macb_suspend(struct device *dev)
 		macb_writel(bp, WOL, MACB_BIT(MAG));
 		enable_irq_wake(bp->queues[0].irq);
 	} else {
+		bp->suspend.ncfgr = macb_readl(bp, NCFGR);
 		if (netif_running(netdev)) {
 			macb_close(netdev);
 		}