[PATCH v6 3/8] reset: Add driver for gpio-controlled reset pins

From: Philipp Zabel <p.zabel@pengutronix.de>
To: linux-arm-kernel@lists.infradead.org, Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Stephen Warren <swarren@wwwdotorg.org>,
	Marek Vasut <marex@denx.de>,
	Fabio Estevam <fabio.estevam@freescale.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Shawn Guo <shawn.guo@linaro.org>,
	kernel@pengutronix.de, devicetree-discuss@lists.ozlabs.org,
	Mike Turquette <mturquette@linaro.org>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	"Rafael J. Wysocki" <rjw@sisk.pl>,
	linux-pm@vger.kernel.org, Philipp Zabel <p.zabel@pengutronix.de>
Subject: [PATCH v6 3/8] reset: Add driver for gpio-controlled reset pins
Date: Thu, 28 Mar 2013 17:35:18 +0100	[thread overview]
Message-ID: <1364488523-20310-4-git-send-email-p.zabel@pengutronix.de> (raw)
In-Reply-To: <1364488523-20310-1-git-send-email-p.zabel@pengutronix.de>

This driver implements a reset controller device that toggles gpios
connected to reset pins of peripheral ICs. The delay between assertion
and de-assertion of the reset signal can be configured.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
---
 .../devicetree/bindings/reset/gpio-reset.txt       |  37 ++++
 drivers/reset/Kconfig                              |  13 ++
 drivers/reset/Makefile                             |   1 +
 drivers/reset/gpio-reset.c                         | 208 +++++++++++++++++++++
 4 files changed, 259 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..1f203eb
--- /dev/null
+++ b/Documentation/devicetree/bindings/reset/gpio-reset.txt
@@ -0,0 +1,37 @@
+GPIO reset controller
+=====================
+
+A GPIO reset controller controls a number of GPIOs that are connected
+to reset pins of peripheral ICs.
+
+Please also refer to reset.txt in this directory for common reset
+controller binding usage.
+
+Required properties:
+- compatible: Should be "gpio-reset"
+- reset-gpios: List of gpios used as reset lines. The gpio specifier for this
+               property depends on the gpio controller that provides the gpio.
+- #reset-cells: 1, see below
+
+Optional properties:
+- reset-delays: List of delays in microseconds. The corresponding gpio reset
+                line should be asserted for this duration to reset.
+- initially-in-reset: List of integers. Zero if the initial state should be
+                      a deasserted reset line, nonzero if the line should be
+                      kept in reset.
+
+example:
+
+gpio_reset: gpio-reset {
+	compatible = "gpio-reset";
+	reset-gpios = <&gpio5 0 1>; /* active-low */
+	reset-delays = <10000>; /* 10 ms */
+	initially-in-reset: <1>;
+	#reset-cells = <1>;
+};
+
+/* Device with nRESET pin connected to GPIO5_0 */
+sii902x@39 {
+	/* ... */
+	resets = <&gpio_reset 0>; /* active-low GPIO5_0, 10 ms reset delay */
+};
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index c9d04f7..e728d36 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -11,3 +11,16 @@ 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 GENERIC_GPIO
+	help
+	  This driver provides support for reset lines that are controlled
+	  directly by GPIOs.
+	  The delay between assertion and de-assertion of the reset signal
+	  can be configured.
+
+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..3e3c363
--- /dev/null
+++ b/drivers/reset/gpio-reset.c
@@ -0,0 +1,208 @@
+/*
+ * 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 {
+	unsigned int gpio;
+	bool active_low;
+};
+
+struct gpio_reset_data {
+	struct reset_controller_dev rcdev;
+	/* these arrays contain a number of elements equal to rcdev.nr_resets */
+	struct gpio_reset *gpios;
+	u32 *delays_us;
+};
+
+static void __gpio_reset_set(struct reset_controller_dev *rcdev,
+		unsigned long gpio_idx, int asserted)
+{
+	struct gpio_reset_data *drvdata = container_of(rcdev,
+			struct gpio_reset_data, rcdev);
+	int value = asserted;
+
+	if (drvdata->gpios[gpio_idx].active_low)
+		value = !value;
+
+	gpio_set_value(drvdata->gpios[gpio_idx].gpio, value);
+}
+
+static int gpio_reset(struct reset_controller_dev *rcdev,
+		unsigned long gpio_idx)
+{
+	struct gpio_reset_data *drvdata = container_of(rcdev,
+			struct gpio_reset_data, rcdev);
+
+	if (gpio_idx >= rcdev->nr_resets)
+		return -EINVAL;
+
+	if (drvdata->delays_us == NULL)
+		return -ENOSYS;
+
+	__gpio_reset_set(rcdev, gpio_idx, 1);
+	udelay(drvdata->delays_us[gpio_idx]);
+	__gpio_reset_set(rcdev, gpio_idx, 0);
+
+	return 0;
+}
+
+static int gpio_reset_assert(struct reset_controller_dev *rcdev,
+		unsigned long gpio_idx)
+{
+	if (gpio_idx >= rcdev->nr_resets)
+		return -EINVAL;
+
+	__gpio_reset_set(rcdev, gpio_idx, 1);
+
+	return 0;
+}
+
+static int gpio_reset_deassert(struct reset_controller_dev *rcdev,
+		unsigned long gpio_idx)
+{
+	if (gpio_idx >= rcdev->nr_resets)
+		return -EINVAL;
+
+	__gpio_reset_set(rcdev, gpio_idx, 0);
+
+	return 0;
+}
+
+static struct reset_control_ops gpio_reset_ops = {
+	.reset = gpio_reset,
+	.assert = gpio_reset_assert,
+	.deassert = gpio_reset_deassert,
+};
+
+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;
+	u32 *initially_in_reset;
+	int nr_gpios;
+	int ret;
+	int i;
+
+	drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
+	if (drvdata == NULL)
+		return -ENOMEM;
+
+	nr_gpios = of_gpio_named_count(np, "reset-gpios");
+	if (nr_gpios < 1)
+		return -EINVAL;
+
+	drvdata->gpios = devm_kzalloc(&pdev->dev, sizeof(struct gpio_reset) *
+			nr_gpios, GFP_KERNEL);
+	if (drvdata->gpios == NULL)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_gpios; i++) {
+		drvdata->gpios[i].gpio = of_get_named_gpio_flags(np,
+				"reset-gpios", i, &flags);
+		if (drvdata->gpios[i].gpio == -EPROBE_DEFER)
+			return drvdata->gpios[i].gpio;
+		else if (drvdata->gpios[i].gpio < 0) {
+			dev_err(&pdev->dev, "invalid gpio for reset %d\n", i);
+			return drvdata->gpios[i].gpio;
+		}
+
+		drvdata->gpios[i].active_low = flags & OF_GPIO_ACTIVE_LOW;
+	}
+
+	if (of_find_property(np, "reset-delays", NULL)) {
+		drvdata->delays_us = devm_kzalloc(&pdev->dev, sizeof(u32) *
+				nr_gpios, GFP_KERNEL);
+		if (drvdata->delays_us == NULL)
+			return -ENOMEM;
+
+		ret = of_property_read_u32_array(np, "reset-delays",
+				drvdata->delays_us, nr_gpios);
+		if (ret < 0)
+			return ret;
+	}
+
+	initially_in_reset = devm_kzalloc(&pdev->dev, sizeof(u32) *
+			nr_gpios, GFP_KERNEL);
+	if (initially_in_reset == NULL)
+		return -ENOMEM;
+	if (of_find_property(np, "initially-in-reset", NULL)) {
+		ret = of_property_read_u32_array(np, "initially-in-reset",
+				initially_in_reset, nr_gpios);
+		if (ret < 0)
+			return ret;
+	}
+
+	for (i = 0; i < nr_gpios; i++) {
+		unsigned long gpio_flags = GPIOF_OUT_INIT_LOW;
+
+		if (drvdata->gpios[i].active_low ^ (!!initially_in_reset[i]))
+			gpio_flags = GPIOF_OUT_INIT_HIGH;
+
+		ret = devm_gpio_request_one(&pdev->dev, drvdata->gpios[i].gpio,
+				gpio_flags, NULL);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "failed to request gpio %d for reset %d\n",
+					drvdata->gpios[i].gpio, i);
+			return ret;
+		}
+	}
+
+	devm_kfree(&pdev->dev, initially_in_reset);
+
+	drvdata->rcdev.of_node = np;
+	drvdata->rcdev.owner = THIS_MODULE;
+	drvdata->rcdev.nr_resets = nr_gpios;
+	drvdata->rcdev.ops = &gpio_reset_ops;
+	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.rc2

