ARM: at91: board-dt-sama5: add phy_fixup to override NAND_Tree

Appearance: On some SAMA5D4EK boards, after power up, the Eth1 doesn't work.

Reason: The PIOE2 pin is connected to the NAND_Tree# of KSZ8081,
But it outputs LOW during the reset period, which cause the NAND_Tree# enabled.

Add phy_fixup() to disable NAND_Tree by overriding the Operation
Mode Strap Override register(i.e. Register 16h) to clear the NAND_Tree bit.
Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/mach-at91/board-dt-sama5.c

@@ -17,6 +17,7 @@
 #include <linux/of_platform.h>
 #include <linux/phy.h>
 #include <linux/clk-provider.h>
+#include <linux/phy.h>
 
 #include <asm/setup.h>
 #include <asm/irq.h>
@@ -26,8 +27,25 @@
 
 #include "generic.h"
 
+static int ksz8081_phy_fixup(struct phy_device *phy)
+{
+	int value;
+
+	value = phy_read(phy, 0x16);
+	value &= ~0x20;
+	phy_write(phy, 0x16, value);
+
+	return 0;
+}
+
 static void __init sama5_dt_device_init(void)
 {
+	if (of_machine_is_compatible("atmel,sama5d4ek") &&
+	   IS_ENABLED(CONFIG_PHYLIB)) {
+		phy_register_fixup_for_id("fc028000.etherne:00",
+						ksz8081_phy_fixup);
+	}
+
 	of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
 }