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Subject[PATCH v3 2/2] reset: Add GPIO support to reset controller framework
Date
This adds support for GPIO controlled reset pins on peripheral ICs to the reset
controller framework. Currently there is no support for specifying a delay
between assertion and de-assertion of the reset signal, so this has to be
handled by the drivers.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
Changes since v2:
- fix assert_prop initial value
---
drivers/reset/Kconfig | 17 ++++++
drivers/reset/Makefile | 9 ++-
drivers/reset/core.c | 29 +++++-----
drivers/reset/gpio-reset.c | 137 +++++++++++++++++++++++++++++++++++++++++++++
drivers/reset/reset-core.h | 47 ++++++++++++++++
5 files changed, 224 insertions(+), 15 deletions(-)
create mode 100644 drivers/reset/gpio-reset.c
create mode 100644 drivers/reset/reset-core.h

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index c9d04f7..a6b12a9 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -10,4 +10,21 @@ menuconfig RESET_CONTROLLER
This framework is designed to abstract reset handling of devices
via GPIOs or SoC-internal reset controller modules.

+ If the device tree contains any resets or reset-gpio properties,
+ this probably should be enabled.
+
If unsure, say no.
+
+if RESET_CONTROLLER
+
+menuconfig RESET_GPIO
+ bool "GPIO Reset Support"
+ depends on GPIOLIB
+ default y if GPIOLIB
+ help
+ GPIO Reset Controller support.
+
+ This option lets the reset controller framework handle reset lines
+ connected to GPIOs.
+
+endif
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index cc29832..764bb74 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -1,2 +1,9 @@
-obj-$(CONFIG_RESET_CONTROLLER) += core.o
+reset-core-objs := core.o
+
+obj-$(CONFIG_RESET_CONTROLLER) += reset-core.o
+
+ifeq ($(CONFIG_RESET_GPIO),y)
+ reset-core-objs += gpio-reset.o
+endif
+
obj-$(CONFIG_ARCH_SUNXI) += reset-sunxi.o
diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index baeaf82..6bfd2d2 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -18,23 +18,12 @@
#include <linux/reset-controller.h>
#include <linux/slab.h>

+#include "reset-core.h"
+
static DEFINE_MUTEX(reset_controller_list_mutex);
static LIST_HEAD(reset_controller_list);

/**
- * struct reset_control - a reset control
- * @rcdev: a pointer to the reset controller device
- * this reset control belongs to
- * @id: ID of the reset controller in the reset
- * controller device
- */
-struct reset_control {
- struct reset_controller_dev *rcdev;
- struct device *dev;
- unsigned int id;
-};
-
-/**
* of_reset_simple_xlate - translate reset_spec to the reset line number
* @rcdev: a pointer to the reset controller device
* @reset_spec: reset line specifier as found in the device tree
@@ -149,6 +138,8 @@ struct reset_control *of_reset_control_get(struct device_node *node,
"reset-names", id);
ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
index, &args);
+ if (index == -EINVAL)
+ return ERR_PTR(-ENOENT);
if (ret)
return ERR_PTR(ret);

@@ -209,6 +200,13 @@ struct reset_control *reset_control_get(struct device *dev, const char *id)
if (!IS_ERR(rstc))
rstc->dev = dev;

+ /*
+ * If there is no dedicated reset controller device, check if we have
+ * a reset line controlled by a GPIO instead.
+ */
+ if (PTR_ERR(rstc) == -ENOENT)
+ return gpio_reset_control_get(dev, id);
+
return rstc;
}
EXPORT_SYMBOL_GPL(reset_control_get);
@@ -223,7 +221,10 @@ void reset_control_put(struct reset_control *rstc)
if (IS_ERR(rstc))
return;

- module_put(rstc->rcdev->owner);
+ if (reset_control_is_gpio(rstc))
+ gpio_reset_control_put(rstc);
+ else
+ module_put(rstc->rcdev->owner);
kfree(rstc);
}
EXPORT_SYMBOL_GPL(reset_control_put);
diff --git a/drivers/reset/gpio-reset.c b/drivers/reset/gpio-reset.c
new file mode 100644
index 0000000..77d4bd7
--- /dev/null
+++ b/drivers/reset/gpio-reset.c
@@ -0,0 +1,137 @@
+/*
+ * GPIO Reset Controller
+ *
+ * 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/device.h>
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/reset-controller.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "reset-core.h"
+
+/*
+ * Global GPIO reset controller
+ */
+static struct reset_controller_dev *gpio_rcdev;
+
+static int gpio_reset_set(struct reset_controller_dev *rcdev,
+ unsigned int gpio, int asserted)
+{
+ struct gpio_desc *gpiod = gpio_to_desc(gpio);
+
+ if (!gpiod)
+ return -EINVAL;
+
+ gpiod_set_value_cansleep(gpiod, asserted);
+
+ return 0;
+}
+
+static int gpio_reset_assert(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ return gpio_reset_set(rcdev, id, 1);
+}
+
+static int gpio_reset_deassert(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ return gpio_reset_set(rcdev, id, 0);
+}
+
+static struct reset_control_ops gpio_reset_ops = {
+ .assert = gpio_reset_assert,
+ .deassert = gpio_reset_deassert,
+};
+
+struct reset_controller_dev *reset_get_gpio_rcdev(void)
+{
+ if (gpio_rcdev)
+ return gpio_rcdev;
+
+ gpio_rcdev = kzalloc(sizeof(*gpio_rcdev), GFP_KERNEL);
+ if (!gpio_rcdev)
+ return NULL;
+
+ gpio_rcdev->owner = THIS_MODULE;
+ gpio_rcdev->ops = &gpio_reset_ops;
+
+ reset_controller_register(gpio_rcdev);
+
+ return gpio_rcdev;
+}
+
+struct reset_control *gpio_reset_control_get(struct device *dev, const char *id)
+{
+ const char *assert_prop = "reset-boot-asserted";
+ const char *gpio_con_id = "reset";
+ struct reset_controller_dev *rcdev;
+ struct reset_control *rstc;
+ struct gpio_desc *gpiod;
+ char scratch[48];
+ bool asserted;
+ int ret;
+
+ if (id) {
+ snprintf(scratch, 48, "%s-reset-boot-asserted", id);
+ assert_prop = scratch;
+ }
+
+ asserted = of_property_read_bool(dev->of_node, assert_prop);
+
+ if (id) {
+ snprintf(scratch, 48, "%s-reset", id);
+ gpio_con_id = scratch;
+ }
+
+ gpiod = gpiod_get(dev, gpio_con_id);
+ if (IS_ERR(gpiod)) {
+ dev_err(dev, "Failed to get GPIO reset: %ld\n", PTR_ERR(gpiod));
+ return ERR_CAST(gpiod);
+ }
+
+ ret = gpiod_direction_output(gpiod, asserted);
+ if (ret < 0)
+ goto err_put;
+
+ ret = -ENOMEM;
+ rcdev = reset_get_gpio_rcdev();
+ if (!rcdev)
+ goto err_put;
+
+ rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
+ if (!rstc)
+ goto err_put;
+
+ rstc->dev = dev;
+ rstc->rcdev = rcdev;
+ rstc->id = desc_to_gpio(gpiod);
+
+ return rstc;
+
+err_put:
+ gpiod_put(gpiod);
+ return ERR_PTR(ret);
+}
+
+bool reset_control_is_gpio(struct reset_control *rstc)
+{
+ return rstc->rcdev == gpio_rcdev;
+}
+
+void gpio_reset_control_put(struct reset_control *rstc)
+{
+ struct gpio_desc *gpiod = gpio_to_desc(rstc->id);
+
+ if (gpiod)
+ gpiod_put(gpiod);
+}
diff --git a/drivers/reset/reset-core.h b/drivers/reset/reset-core.h
new file mode 100644
index 0000000..55bd297
--- /dev/null
+++ b/drivers/reset/reset-core.h
@@ -0,0 +1,47 @@
+/*
+ * Reset Controller framework
+ *
+ * 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.
+ */
+
+#ifndef __RESET_CORE_H__
+#define __RESET_CORE_H__
+
+/**
+ * struct reset_control - a reset control
+ * @rcdev: a pointer to the reset controller device
+ * this reset control belongs to
+ * @id: ID of the reset controller in the reset
+ * controller device
+ */
+struct reset_control {
+ struct reset_controller_dev *rcdev;
+ struct device *dev;
+ unsigned int id;
+};
+
+#if IS_ENABLED(CONFIG_RESET_GPIO)
+struct reset_control *gpio_reset_control_get(struct device *dev, const char *id);
+bool reset_control_is_gpio(struct reset_control *rstc);
+void gpio_reset_control_put(struct reset_control *rstc);
+#else
+static inline struct reset_control *gpio_reset_control_get(struct device *dev,
+ const char *id)
+{
+ return -ENOSYS;
+}
+
+static inline bool reset_control_is_gpio(struct reset_control *rstc)
+{
+ return false;
+}
+
+static inline void gpio_reset_control_put(struct reset_control *rstc) { }
+#endif
+
+#endif
--
1.8.5.2


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