reset: Add a driver for the reset controller on the AR71XX/AR9XXX

The AR71XX/AR9XXX SoC have a simple reset controller with one bit per
reset line.
Signed-off-by: Alban Bedel <albeu@free.fr>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

arch/mips/Kconfig

@@ -118,6 +118,7 @@ config ATH25
 
 config ATH79
 	bool "Atheros AR71XX/AR724X/AR913X based boards"
+	select ARCH_HAS_RESET_CONTROLLER
 	select ARCH_REQUIRE_GPIOLIB
 	select BOOT_RAW
 	select CEVT_R4K

drivers/reset/Makefile

@@ -3,3 +3,4 @@ obj-$(CONFIG_ARCH_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_ARCH_BERLIN) += reset-berlin.o
 obj-$(CONFIG_ARCH_SUNXI) += reset-sunxi.o
 obj-$(CONFIG_ARCH_STI) += sti/
+obj-$(CONFIG_ATH79) += reset-ath79.o

drivers/reset/reset-ath79.c

+/*
+ * Copyright (C) 2015 Alban Bedel <albeu@free.fr>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+
+struct ath79_reset {
+	struct reset_controller_dev rcdev;
+	void __iomem *base;
+	spinlock_t lock;
+};
+
+static int ath79_reset_update(struct reset_controller_dev *rcdev,
+			unsigned long id, bool assert)
+{
+	struct ath79_reset *ath79_reset =
+		container_of(rcdev, struct ath79_reset, rcdev);
+	unsigned long flags;
+	u32 val;
+
+	spin_lock_irqsave(&ath79_reset->lock, flags);
+	val = readl(ath79_reset->base);
+	if (assert)
+		val |= BIT(id);
+	else
+		val &= ~BIT(id);
+	writel(val, ath79_reset->base);
+	spin_unlock_irqrestore(&ath79_reset->lock, flags);
+
+	return 0;
+}
+
+static int ath79_reset_assert(struct reset_controller_dev *rcdev,
+			unsigned long id)
+{
+	return ath79_reset_update(rcdev, id, true);
+}
+
+static int ath79_reset_deassert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	return ath79_reset_update(rcdev, id, false);
+}
+
+static int ath79_reset_status(struct reset_controller_dev *rcdev,
+			unsigned long id)
+{
+	struct ath79_reset *ath79_reset =
+		container_of(rcdev, struct ath79_reset, rcdev);
+	u32 val;
+
+	val = readl(ath79_reset->base);
+
+	return !!(val & BIT(id));
+}
+
+static struct reset_control_ops ath79_reset_ops = {
+	.assert = ath79_reset_assert,
+	.deassert = ath79_reset_deassert,
+	.status = ath79_reset_status,
+};
+
+static int ath79_reset_probe(struct platform_device *pdev)
+{
+	struct ath79_reset *ath79_reset;
+	struct resource *res;
+
+	ath79_reset = devm_kzalloc(&pdev->dev,
+				sizeof(*ath79_reset), GFP_KERNEL);
+	if (!ath79_reset)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, ath79_reset);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	ath79_reset->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(ath79_reset->base))
+		return PTR_ERR(ath79_reset->base);
+
+	ath79_reset->rcdev.ops = &ath79_reset_ops;
+	ath79_reset->rcdev.owner = THIS_MODULE;
+	ath79_reset->rcdev.of_node = pdev->dev.of_node;
+	ath79_reset->rcdev.of_reset_n_cells = 1;
+	ath79_reset->rcdev.nr_resets = 32;
+
+	return reset_controller_register(&ath79_reset->rcdev);
+}
+
+static int ath79_reset_remove(struct platform_device *pdev)
+{
+	struct ath79_reset *ath79_reset = platform_get_drvdata(pdev);
+
+	reset_controller_unregister(&ath79_reset->rcdev);
+
+	return 0;
+}
+
+static const struct of_device_id ath79_reset_dt_ids[] = {
+	{ .compatible = "qca,ar7100-reset", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ath79_reset_dt_ids);
+
+static struct platform_driver ath79_reset_driver = {
+	.probe	= ath79_reset_probe,
+	.remove = ath79_reset_remove,
+	.driver = {
+		.name		= "ath79-reset",
+		.of_match_table	= ath79_reset_dt_ids,
+	},
+};
+module_platform_driver(ath79_reset_driver);
+
+MODULE_AUTHOR("Alban Bedel <albeu@free.fr>");
+MODULE_DESCRIPTION("AR71xx Reset Controller Driver");
+MODULE_LICENSE("GPL");