MIPS: Lantiq: Adds minimal dcdc driver

This driver so far only reads the core voltage.
Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5677/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/lantiq/xway/Makefile

-obj-y := prom.o sysctrl.o clk.o reset.o dma.o gptu.o
+obj-y := prom.o sysctrl.o clk.o reset.o dma.o gptu.o dcdc.o
 
 obj-$(CONFIG_XRX200_PHY_FW) += xrx200_phy_fw.o

arch/mips/lantiq/xway/dcdc.c

+/*
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  Copyright (C) 2012 John Crispin <blogic@openwrt.org>
+ *  Copyright (C) 2010 Sameer Ahmad, Lantiq GmbH
+ */
+
+#include <linux/ioport.h>
+#include <linux/of_platform.h>
+
+#include <lantiq_soc.h>
+
+/* Bias and regulator Setup Register */
+#define DCDC_BIAS_VREG0	0xa
+/* Bias and regulator Setup Register */
+#define DCDC_BIAS_VREG1	0xb
+
+#define dcdc_w8(x, y)	ltq_w8((x), dcdc_membase + (y))
+#define dcdc_r8(x)	ltq_r8(dcdc_membase + (x))
+
+static void __iomem *dcdc_membase;
+
+static int dcdc_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	dcdc_membase = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(dcdc_membase))
+		return PTR_ERR(dcdc_membase);
+
+	dev_info(&pdev->dev, "Core Voltage : %d mV\n",
+		dcdc_r8(DCDC_BIAS_VREG1) * 8);
+
+	return 0;
+}
+
+static const struct of_device_id dcdc_match[] = {
+	{ .compatible = "lantiq,dcdc-xrx200" },
+	{},
+};
+
+static struct platform_driver dcdc_driver = {
+	.probe = dcdc_probe,
+	.driver = {
+		.name = "dcdc-xrx200",
+		.owner = THIS_MODULE,
+		.of_match_table = dcdc_match,
+	},
+};
+
+int __init dcdc_init(void)
+{
+	int ret = platform_driver_register(&dcdc_driver);
+
+	if (ret)
+		pr_info("dcdc: Error registering platform driver\n");
+	return ret;
+}
+
+arch_initcall(dcdc_init);