ARM: meson: Add reset controller

This patch adds support for the reset controller found on the Amlogic MesonX SoCs. For several devices in the AO (Always-On) power domain, it is possible to reset them by programming a specific bit in a register.

Signed-off-by Carlo Caione <[email protected]>

---
 drivers/reset/Makefile      |   1 +
 drivers/reset/reset-meson.c | 142 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 143 insertions(+)
 create mode 100644 drivers/reset/reset-meson.c

drivers/reset/Makefile +1 -0

index 60fed3d..74f2372 100644
@@ -1,4 +1,5 @@
 obj-$(CONFIG_RESET_CONTROLLER) += core.o
 obj-$(CONFIG_ARCH_SOCFPGA) += reset-socfpga.o
 obj-$(CONFIG_ARCH_SUNXI) += reset-sunxi.o
+obj-$(CONFIG_ARCH_MESON) += reset-meson.o
 obj-$(CONFIG_ARCH_STI) += sti/

drivers/reset/reset-meson.c new file +0 -0

new file mode 100644
index 0000000..59b58e4

drivers/reset/reset-meson.c new file +6 -0

+ * 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.
+ */
+

drivers/reset/reset-meson.c new file +72 -0

+struct meson_reset_data {
+	spinlock_t			lock;
+	void __iomem			*membase;
+	struct reset_controller_dev	rcdev;
+};
+
+static int meson_reset_assert(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	struct meson_reset_data *data = container_of(rcdev,
+						     struct meson_reset_data,
+						     rcdev);
+	unsigned long flags;
+	u32 reg;
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	reg = readl(data->membase + MESON_RST_OFFSET);
+	writel(reg | BIT(id), data->membase + MESON_RST_OFFSET);
+
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	return 0;
+}
+
+static int meson_reset_deassert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	struct meson_reset_data *data = container_of(rcdev,
+						     struct meson_reset_data,
+						     rcdev);
+
+	unsigned long flags;
+	u32 reg;
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	reg = readl(data->membase + MESON_RST_OFFSET);
+	writel(reg & ~BIT(id), data->membase + MESON_RST_OFFSET);
+
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	return 0;
+}
+
+static int meson_reset_dev(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	int err;
+
+	err = meson_reset_assert(rcdev, id);
+	if (err)
+		return err;
+
+	return meson_reset_deassert(rcdev, id);
+}
+
+static struct reset_control_ops meson_reset_ops = {
+	.assert		= meson_reset_assert,
+	.deassert	= meson_reset_deassert,
+	.reset		= meson_reset_dev,
+};
+
+static int meson_reset_probe(struct platform_device *pdev)
+{
+	struct meson_reset_data *data;
+	struct resource *res;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

drivers/reset/reset-meson.c new file +33 -0

+	data->rcdev.ops = &meson_reset_ops;
+	data->rcdev.of_node = pdev->dev.of_node;
+
+	return reset_controller_register(&data->rcdev);
+}
+
+static int meson_reset_remove(struct platform_device *pdev)
+{
+	struct meson_reset_data *data = platform_get_drvdata(pdev);
+
+	reset_controller_unregister(&data->rcdev);
+
+	return 0;
+}
+
+static const struct of_device_id meson_reset_dt_ids[] = {
+	{ .compatible = "amlogic,meson6-rst-mgr-ao", },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver meson_reset_driver = {
+	.probe	= meson_reset_probe,
+	.remove	= meson_reset_remove,
+	.driver = {
+		.name		= "meson-reset",
+		.of_match_table	= meson_reset_dt_ids,
+	},
+};
+module_platform_driver(meson_reset_driver);
+
+MODULE_AUTHOR("Carlo Caione <[email protected]>");
+MODULE_DESCRIPTION("Meson Reset Controller Driver");
+MODULE_LICENSE("GPL");

Signature · 1 line

1.9.1

Hi Carlo,

drivers/reset/reset-meson.c line 5

Quoted 6 lines

drivers/reset/reset-meson.c new file +5 -0

@@ -0,0 +1,142 @@
+/*
+ * Copyright 2014 Carlo Caione <[email protected]>
+ *
+ * based on
+ * Steffen Trumtrar Reset Controller driver

That doesn't sound right. Do you mean socfpga-reset?

drivers/reset/reset-meson.c line 9

Quoted 3 lines

drivers/reset/reset-meson.c new file +3 -0

+ * Copyright 2014 Steffen Trumtrar
+ *
+ * Steffen Trumtrar <[email protected]>

Could be combined into a single line.

Quoted 10 lines

drivers/reset/reset-meson.c new file +10 -0

+ * 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.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>

drivers/reset/reset-meson.c line 26

Quoted 6 lines

drivers/reset/reset-meson.c new file +6 -0

+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#define MESON_RST_OFFSET     0x00

If there is only one register, I see no need for this.

drivers/reset/reset-meson.c line 109

Quoted 3 lines

drivers/reset/reset-meson.c new file +3 -0

+
+     data->rcdev.owner = THIS_MODULE;
+     data->rcdev.nr_resets = BITS_PER_LONG;

Are all bits in this registers reset controls (or rather, are you positive there is no bit in this register used by anything else)?

Other than that, the driver looks good.

Add the node for the reset controller in the DTSI.

Signed-off-by Carlo Caione <[email protected]>

---
 arch/arm/boot/dts/meson.dtsi | 6 ++++++
 1 file changed, 6 insertions(+)

arch/arm/boot/dts/meson.dtsi +0 -0

index e6539ea..1ca864e 100644
@@ -75,6 +75,12 @@
 			reg = <0xc1109900 0x8>;
 		};