net: macb: Properly handle phylink on at91sam9x

I just recently noticed that ethernet does not work anymore since v5.5
on the GARDENA smart Gateway, which is based on the AT91SAM9G25.
Debugging showed that the "GEM bits" in the NCFGR register are now
unconditionally accessed, which is incorrect for the !macb_is_gem()
case.

This patch adds the macb_is_gem() checks back to the code
(in macb_mac_config() & macb_mac_link_up()), so that the GEM register
bits are not accessed in this case any more.

Fixes: 7897b071 ("net: macb: convert to phylink")
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Reto Schneider <reto.schneider@husqvarnagroup.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -578,7 +578,7 @@ static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 	if (bp->caps & MACB_CAPS_MACB_IS_EMAC) {
 		if (state->interface == PHY_INTERFACE_MODE_RMII)
 			ctrl |= MACB_BIT(RM9200_RMII);
-	} else {
+	} else if (macb_is_gem(bp)) {
 		ctrl &= ~(GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL));
 
 		if (state->interface == PHY_INTERFACE_MODE_SGMII)
@@ -639,10 +639,13 @@ static void macb_mac_link_up(struct phylink_config *config,
 		ctrl |= MACB_BIT(FD);
 
 	if (!(bp->caps & MACB_CAPS_MACB_IS_EMAC)) {
-		ctrl &= ~(GEM_BIT(GBE) | MACB_BIT(PAE));
+		ctrl &= ~MACB_BIT(PAE);
+		if (macb_is_gem(bp)) {
+			ctrl &= ~GEM_BIT(GBE);
 
-		if (speed == SPEED_1000)
-			ctrl |= GEM_BIT(GBE);
+			if (speed == SPEED_1000)
+				ctrl |= GEM_BIT(GBE);
+		}
 
 		/* We do not support MLO_PAUSE_RX yet */
 		if (tx_pause)