[PATCH v4 8/8] reset: Add driver for gpio-controlled reset pins
Philipp Zabel
p.zabel at pengutronix.de
Tue Feb 26 06:39:34 EST 2013
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 at pengutronix.de>
---
Changes since v3:
- Switched reset-delays property from milliseconds to microseconds
and declared it optional.
- Added initially-in-reset property.
- Handle of_get_named_gpio_flags returning EPROBE_DEFER silently.
- Store bool active_low instead of gpio flags in struct reset_gpio.
- Moved delay out of struct gpio_reset into its own array.
- Use rcdev.nr_resets instead of nr_gpios to keep a count of array
elements.
- Let gpio_reset_set take struct reset_controller_dev directly,
simplifying gpio_reset_assert and gpio_reset_deassert.
- First call of_get_named_gpio_flags on all gpios to determine
if any return EPROBE_DEFER - only then parse the reset-delays
and initially-in-reset properties, finally request the gpios.
- Add MODULE_* annotation
---
.../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 at 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 at pengutronix.de>");
+MODULE_DESCRIPTION("gpio reset controller");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:gpio-reset");
+MODULE_DEVICE_TABLE(of, gpio_reset_dt_ids);
--
1.7.10.4
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