net: macb: Properly handle phylink on at91rm9200

at91ether_init was handling the phy mode and speed but since the switch to
phylink, the NCFGR register got overwritten by macb_mac_config(). The issue
is that the RM9200_RMII bit and the MACB_CLK_DIV32 field are cleared
but never restored as they conflict with the PAE, GBE and PCSSEL bits.

Add new capability to differentiate between EMAC and the other versions of
the IP and use it to set and avoid clearing the relevant bits.

Also, this fixes a NULL pointer dereference in macb_mac_link_up as the EMAC
doesn't use any rings/bufffers/queues.

Fixes: 7897b071 ("net: macb: convert to phylink")
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb.h

@@ -652,6 +652,7 @@
 #define MACB_CAPS_GEM_HAS_PTP			0x00000040
 #define MACB_CAPS_BD_RD_PREFETCH		0x00000080
 #define MACB_CAPS_NEEDS_RSTONUBR		0x00000100
+#define MACB_CAPS_MACB_IS_EMAC			0x08000000
 #define MACB_CAPS_FIFO_MODE			0x10000000
 #define MACB_CAPS_GIGABIT_MODE_AVAILABLE	0x20000000
 #define MACB_CAPS_SG_DISABLED			0x40000000

drivers/net/ethernet/cadence/macb_main.c

@@ -572,16 +572,13 @@ static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 	old_ctrl = ctrl = macb_or_gem_readl(bp, NCFGR);
 
 	/* Clear all the bits we might set later */
-	ctrl &= ~(GEM_BIT(GBE) | MACB_BIT(SPD) | MACB_BIT(FD) | MACB_BIT(PAE) |
-		  GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL));
+	ctrl &= ~(MACB_BIT(SPD) | MACB_BIT(FD) | MACB_BIT(PAE));
 
-	if (state->speed == SPEED_1000)
-		ctrl |= GEM_BIT(GBE);
-	else if (state->speed == SPEED_100)
-		ctrl |= MACB_BIT(SPD);
-
-	if (state->duplex)
-		ctrl |= MACB_BIT(FD);
+	if (bp->caps & MACB_CAPS_MACB_IS_EMAC) {
+		if (state->interface == PHY_INTERFACE_MODE_RMII)
+			ctrl |= MACB_BIT(RM9200_RMII);
+	} else {
+		ctrl &= ~(GEM_BIT(GBE) | GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL));
 
 		/* We do not support MLO_PAUSE_RX yet */
 		if (state->pause & MLO_PAUSE_TX)
@@ -589,6 +586,15 @@ static void macb_mac_config(struct phylink_config *config, unsigned int mode,
 
 		if (state->interface == PHY_INTERFACE_MODE_SGMII)
 			ctrl |= GEM_BIT(SGMIIEN) | GEM_BIT(PCSSEL);
+	}
+
+	if (state->speed == SPEED_1000)
+		ctrl |= GEM_BIT(GBE);
+	else if (state->speed == SPEED_100)
+		ctrl |= MACB_BIT(SPD);
+
+	if (state->duplex)
+		ctrl |= MACB_BIT(FD);
 
 	/* Apply the new configuration, if any */
 	if (old_ctrl ^ ctrl)
@@ -608,6 +614,7 @@ static void macb_mac_link_down(struct phylink_config *config, unsigned int mode,
 	unsigned int q;
 	u32 ctrl;
 
+	if (!(bp->caps & MACB_CAPS_MACB_IS_EMAC))
 		for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)
 			queue_writel(queue, IDR,
 				     bp->rx_intr_mask | MACB_TX_INT_FLAGS | MACB_BIT(HRESP));
@@ -627,6 +634,7 @@ static void macb_mac_link_up(struct phylink_config *config, unsigned int mode,
 	struct macb_queue *queue;
 	unsigned int q;
 
+	if (!(bp->caps & MACB_CAPS_MACB_IS_EMAC)) {
 		macb_set_tx_clk(bp->tx_clk, bp->speed, ndev);
 
 		/* Initialize rings & buffers as clearing MACB_BIT(TE) in link down
@@ -638,6 +646,7 @@ static void macb_mac_link_up(struct phylink_config *config, unsigned int mode,
 		for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)
 			queue_writel(queue, IER,
 				     bp->rx_intr_mask | MACB_TX_INT_FLAGS | MACB_BIT(HRESP));
+	}
 
 	/* Enable Rx and Tx */
 	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(RE) | MACB_BIT(TE));
@@ -4041,7 +4050,6 @@ static int at91ether_init(struct platform_device *pdev)
 	struct net_device *dev = platform_get_drvdata(pdev);
 	struct macb *bp = netdev_priv(dev);
 	int err;
-	u32 reg;
 
 	bp->queues[0].bp = bp;
 
@@ -4055,11 +4063,7 @@ static int at91ether_init(struct platform_device *pdev)
 
 	macb_writel(bp, NCR, 0);
 
-	reg = MACB_BF(CLK, MACB_CLK_DIV32) | MACB_BIT(BIG);
-	if (bp->phy_interface == PHY_INTERFACE_MODE_RMII)
-		reg |= MACB_BIT(RM9200_RMII);
-
-	macb_writel(bp, NCFGR, reg);
+	macb_writel(bp, NCFGR, MACB_BF(CLK, MACB_CLK_DIV32) | MACB_BIT(BIG));
 
 	return 0;
 }
@@ -4218,7 +4222,7 @@ static const struct macb_config sama5d4_config = {
 };
 
 static const struct macb_config emac_config = {
-	.caps = MACB_CAPS_NEEDS_RSTONUBR,
+	.caps = MACB_CAPS_NEEDS_RSTONUBR | MACB_CAPS_MACB_IS_EMAC,
 	.clk_init = at91ether_clk_init,
 	.init = at91ether_init,
 };