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From 31bacc8256b3ddb19269a3a1c74b0ba3851d1e19 Mon Sep 17 00:00:00 2001
From: Philipp Zabel <p.zabel@pengutronix.de>
Date: Tue, 28 May 2013 17:06:15 +0200
Subject: [PATCH] reset: Add driver for gpio-controlled reset pins
This driver implements a reset controller device that toggle a gpio
connected to a reset pin of a peripheral IC. The delay between assertion
and de-assertion of the reset signal can be configured via device tree.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
---
.../devicetree/bindings/reset/gpio-reset.txt | 35 +++++
drivers/reset/Kconfig | 11 ++
drivers/reset/Makefile | 1 +
drivers/reset/gpio-reset.c | 169 +++++++++++++++++++++
4 files changed, 216 insertions(+)
create mode 100644 Documentation/devicetree/bindings/reset/gpio-reset.txt
create mode 100644 drivers/reset/gpio-reset.c
diff --git a/Documentation/devicetree/bindings/reset/gpio-reset.txt b/Documentation/devicetree/bindings/reset/gpio-reset.txt
new file mode 100644
index 0000000..bca5348
--- /dev/null
+++ b/Documentation/devicetree/bindings/reset/gpio-reset.txt
@@ -0,0 +1,35 @@
+GPIO reset controller
+=====================
+
+A GPIO reset controller controls a single GPIO that is connected to the reset
+pin of a peripheral IC. Please also refer to reset.txt in this directory for
+common reset controller binding usage.
+
+Required properties:
+- compatible: Should be "gpio-reset"
+- reset-gpios: A gpio used as reset line. The gpio specifier for this property
+ depends on the gpio controller that provides the gpio.
+- #reset-cells: 0, see below
+
+Optional properties:
+- reset-delay-us: delay in microseconds. The gpio reset line will be asserted for
+ this duration to reset.
+- initially-in-reset: boolean. If not set, the initial state should be a
+ deasserted reset line. If this property exists, the
+ reset line should be kept in reset.
+
+example:
+
+sii902x_reset: gpio-reset {
+ compatible = "gpio-reset";
+ reset-gpios = <&gpio5 0 GPIO_ACTIVE_LOW>;
+ reset-delay-us = <10000>;
+ initially-in-reset;
+ #reset-cells = <0>;
+};
+
+/* Device with nRESET pin connected to GPIO5_0 */
+sii902x@39 {
+ /* ... */
+ resets = <&sii902x_reset>; /* active-low GPIO5_0, 10 ms delay */
+};
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index c9d04f7..1a862df 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -11,3 +11,14 @@ menuconfig RESET_CONTROLLER
via GPIOs or SoC-internal reset controller modules.
If unsure, say no.
+
+if RESET_CONTROLLER
+
+config RESET_GPIO
+ tristate "GPIO reset controller support"
+ depends on GPIOLIB && OF
+ help
+ This driver provides support for reset lines that are controlled
+ directly by GPIOs.
+
+endif
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 1e2d83f..b854f20 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -1 +1,2 @@
obj-$(CONFIG_RESET_CONTROLLER) += core.o
+obj-$(CONFIG_RESET_GPIO) += gpio-reset.o
diff --git a/drivers/reset/gpio-reset.c b/drivers/reset/gpio-reset.c
new file mode 100644
index 0000000..acc1076
--- /dev/null
+++ b/drivers/reset/gpio-reset.c
@@ -0,0 +1,169 @@
+/*
+ * GPIO Reset Controller driver
+ *
+ * Copyright 2013 Philipp Zabel, Pengutronix
+ *
+ * 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/delay.h>
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+
+struct gpio_reset_data {
+ struct reset_controller_dev rcdev;
+ unsigned int gpio;
+ bool active_low;
+ u32 delay_us;
+};
+
+static void __gpio_reset_set(struct reset_controller_dev *rcdev, int asserted)
+{
+ struct gpio_reset_data *drvdata = container_of(rcdev,
+ struct gpio_reset_data, rcdev);
+ int value = asserted;
+
+ if (drvdata->active_low)
+ value = !value;
+
+ gpio_set_value(drvdata->gpio, value);
+}
+
+static int gpio_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+ struct gpio_reset_data *drvdata = container_of(rcdev,
+ struct gpio_reset_data, rcdev);
+
+ if (drvdata->delay_us < 0)
+ return -ENOSYS;
+
+ __gpio_reset_set(rcdev, 1);
+ udelay(drvdata->delay_us);
+ __gpio_reset_set(rcdev, 0);
+
+ return 0;
+}
+
+static int gpio_reset_assert(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ __gpio_reset_set(rcdev, 1);
+
+ return 0;
+}
+
+static int gpio_reset_deassert(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ __gpio_reset_set(rcdev, 0);
+
+ return 0;
+}
+
+static struct reset_control_ops gpio_reset_ops = {
+ .reset = gpio_reset,
+ .assert = gpio_reset_assert,
+ .deassert = gpio_reset_deassert,
+};
+
+static int of_gpio_reset_xlate(struct reset_controller_dev *rcdev,
+ const struct of_phandle_args *reset_spec)
+{
+ if (WARN_ON(reset_spec->args_count != 0))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int gpio_reset_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct gpio_reset_data *drvdata;
+ enum of_gpio_flags flags;
+ unsigned long gpio_flags;
+ bool initially_in_reset;
+ int ret;
+
+ drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
+ if (drvdata == NULL)
+ return -ENOMEM;
+
+ if (of_gpio_named_count(np, "reset-gpios") != 1)
+ return -EINVAL;
+
+ drvdata->gpio = of_get_named_gpio_flags(np, "reset-gpios", 0, &flags);
+ if (drvdata->gpio == -EPROBE_DEFER) {
+ return drvdata->gpio;
+ } else if (!gpio_is_valid(drvdata->gpio)) {
+ dev_err(&pdev->dev, "invalid reset gpio: %d\n", drvdata->gpio);
+ return drvdata->gpio;
+ }
+
+ drvdata->active_low = flags & OF_GPIO_ACTIVE_LOW;
+
+ ret = of_property_read_u32(np, "reset-delay-us", &drvdata->delay_us);
+ if (ret < 0)
+ return ret;
+
+ initially_in_reset = of_property_read_bool(np, "initially-in-reset");
+ if (drvdata->active_low ^ initially_in_reset)
+ gpio_flags = GPIOF_OUT_INIT_HIGH;
+ else
+ gpio_flags = GPIOF_OUT_INIT_LOW;
+
+ ret = devm_gpio_request_one(&pdev->dev, drvdata->gpio, gpio_flags, NULL);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "failed to request gpio %d: %d\n",
+ drvdata->gpio, ret);
+ return ret;
+ }
+
+ drvdata->rcdev.of_node = np;
+ drvdata->rcdev.owner = THIS_MODULE;
+ drvdata->rcdev.nr_resets = 1;
+ drvdata->rcdev.ops = &gpio_reset_ops;
+ drvdata->rcdev.of_xlate = of_gpio_reset_xlate;
+ reset_controller_register(&drvdata->rcdev);
+
+ platform_set_drvdata(pdev, drvdata);
+
+ return 0;
+}
+
+static int gpio_reset_remove(struct platform_device *pdev)
+{
+ struct gpio_reset_data *drvdata = platform_get_drvdata(pdev);
+
+ reset_controller_unregister(&drvdata->rcdev);
+
+ return 0;
+}
+
+static struct of_device_id gpio_reset_dt_ids[] = {
+ { .compatible = "gpio-reset" },
+ { }
+};
+
+static struct platform_driver gpio_reset_driver = {
+ .probe = gpio_reset_probe,
+ .remove = gpio_reset_remove,
+ .driver = {
+ .name = "gpio-reset",
+ .owner = THIS_MODULE,
+ .of_match_table = of_match_ptr(gpio_reset_dt_ids),
+ },
+};
+
+module_platform_driver(gpio_reset_driver);
+
+MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
+MODULE_DESCRIPTION("gpio reset controller");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:gpio-reset");
+MODULE_DEVICE_TABLE(of, gpio_reset_dt_ids);
--
1.8.2.1
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