ARM: tegra: enable PCIe controller on p2771-0000

p2771-0000 has a couple of PCIe ports; one physically x4 desktop PCI
connector (which may run at x2 electrically, depending on the board
version and configuration) and a x1 connection to the M.2 slot (which may
not be active, depending on the board version and configuration). This
change enables those.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/board/nvidia/p2771-0000/p2771-0000.c b/board/nvidia/p2771-0000/p2771-0000.c
index 0c828a2..529ed9d 100644
--- a/board/nvidia/p2771-0000/p2771-0000.c
+++ b/board/nvidia/p2771-0000/p2771-0000.c
@@ -31,3 +31,25 @@
 
 	return 0;
 }
+
+int tegra_pcie_board_init(void)
+{
+	struct udevice *dev;
+	uchar val;
+	int ret;
+
+	/* Turn on MAX77620 LDO7 to 1.05V for PEX power */
+	debug("%s: Set LDO7 for PEX power to 1.05V\n", __func__);
+	ret = i2c_get_chip_for_busnum(0, MAX77620_I2C_ADDR_7BIT, 1, &dev);
+	if (ret) {
+		printf("%s: Cannot find MAX77620 I2C chip\n", __func__);
+		return -1;
+	}
+	/* 0xC5 for 1.05v, enabled: bit7:6 = 11 = enable, bit5:0 = voltage */
+	val = 0xC5;
+	ret = dm_i2c_write(dev, MAX77620_CNFG1_L7_REG, &val, 1);
+	if (ret)
+		printf("i2c_write 0 0x3c 0x31 failed: %d\n", ret);
+
+	return 0;
+}