reset: Add reset controller API

This adds a simple API for devices to request being reset
by separate reset controller hardware and implements the
reset signal device tree binding.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Pavel Machek <pavel@ucw.cz>

3 files changed, 311 insertions, 0 deletions

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
new file mode 100644
index 000000000000..c9d04f797862
--- /dev/null
+++ b/drivers/reset/Kconfig
@@ -0,0 +1,13 @@
+config ARCH_HAS_RESET_CONTROLLER
+        bool
+
+menuconfig RESET_CONTROLLER
+        bool "Reset Controller Support"
+        default y if ARCH_HAS_RESET_CONTROLLER
+        help
+          Generic Reset Controller support.
+
+          This framework is designed to abstract reset handling of devices
+          via GPIOs or SoC-internal reset controller modules.
+
+          If unsure, say no.
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
new file mode 100644
index 000000000000..1e2d83f2b995
--- /dev/null
+++ b/drivers/reset/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_RESET_CONTROLLER) += core.o
diff --git a/drivers/reset/core.c b/drivers/reset/core.c
new file mode 100644
index 000000000000..a258277959b4
--- /dev/null
+++ b/drivers/reset/core.c
@@ -0,0 +1,297 @@
+/*
+ * 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.
+ */
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/reset.h>
+#include <linux/reset-controller.h>
+#include <linux/slab.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
+ * @flags: a flags pointer to fill in (optional)
+ *
+ * This simple translation function should be used for reset controllers
+ * with 1:1 mapping, where reset lines can be indexed by number without gaps.
+ */
+int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
+                          const struct of_phandle_args *reset_spec)
+{
+        if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
+                return -EINVAL;
+
+        if (reset_spec->args[0] >= rcdev->nr_resets)
+                return -EINVAL;
+
+        return reset_spec->args[0];
+}
+EXPORT_SYMBOL_GPL(of_reset_simple_xlate);
+
+/**
+ * reset_controller_register - register a reset controller device
+ * @rcdev: a pointer to the initialized reset controller device
+ */
+int reset_controller_register(struct reset_controller_dev *rcdev)
+{
+        if (!rcdev->of_xlate) {
+                rcdev->of_reset_n_cells = 1;
+                rcdev->of_xlate = of_reset_simple_xlate;
+        }
+
+        mutex_lock(&reset_controller_list_mutex);
+        list_add(&rcdev->list, &reset_controller_list);
+        mutex_unlock(&reset_controller_list_mutex);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(reset_controller_register);
+
+/**
+ * reset_controller_unregister - unregister a reset controller device
+ * @rcdev: a pointer to the reset controller device
+ */
+void reset_controller_unregister(struct reset_controller_dev *rcdev)
+{
+        mutex_lock(&reset_controller_list_mutex);
+        list_del(&rcdev->list);
+        mutex_unlock(&reset_controller_list_mutex);
+}
+EXPORT_SYMBOL_GPL(reset_controller_unregister);
+
+/**
+ * reset_control_reset - reset the controlled device
+ * @rstc: reset controller
+ */
+int reset_control_reset(struct reset_control *rstc)
+{
+        if (rstc->rcdev->ops->reset)
+                return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
+
+        return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(reset_control_reset);
+
+/**
+ * reset_control_assert - asserts the reset line
+ * @rstc: reset controller
+ */
+int reset_control_assert(struct reset_control *rstc)
+{
+        if (rstc->rcdev->ops->assert)
+                return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
+
+        return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(reset_control_assert);
+
+/**
+ * reset_control_deassert - deasserts the reset line
+ * @rstc: reset controller
+ */
+int reset_control_deassert(struct reset_control *rstc)
+{
+        if (rstc->rcdev->ops->deassert)
+                return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
+
+        return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(reset_control_deassert);
+
+/**
+ * reset_control_get - Lookup and obtain a reference to a reset controller.
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Returns a struct reset_control or IS_ERR() condition containing errno.
+ *
+ * Use of id names is optional.
+ */
+struct reset_control *reset_control_get(struct device *dev, const char *id)
+{
+        struct reset_control *rstc = ERR_PTR(-EPROBE_DEFER);
+        struct reset_controller_dev *r, *rcdev;
+        struct of_phandle_args args;
+        int index = 0;
+        int rstc_id;
+        int ret;
+
+        if (!dev)
+                return ERR_PTR(-EINVAL);
+
+        if (id)
+                index = of_property_match_string(dev->of_node,
+                                                 "reset-names", id);
+        ret = of_parse_phandle_with_args(dev->of_node, "resets", "#reset-cells",
+                                         index, &args);
+        if (ret)
+                return ERR_PTR(ret);
+
+        mutex_lock(&reset_controller_list_mutex);
+        rcdev = NULL;
+        list_for_each_entry(r, &reset_controller_list, list) {
+                if (args.np == r->of_node) {
+                        rcdev = r;
+                        break;
+                }
+        }
+        of_node_put(args.np);
+
+        if (!rcdev) {
+                mutex_unlock(&reset_controller_list_mutex);
+                return ERR_PTR(-ENODEV);
+        }
+
+        rstc_id = rcdev->of_xlate(rcdev, &args);
+        if (rstc_id < 0) {
+                mutex_unlock(&reset_controller_list_mutex);
+                return ERR_PTR(rstc_id);
+        }
+
+        try_module_get(rcdev->owner);
+        mutex_unlock(&reset_controller_list_mutex);
+
+        rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
+        if (!rstc) {
+                module_put(rstc->rcdev->owner);
+                return ERR_PTR(-ENOMEM);
+        }
+
+        rstc->dev = dev;
+        rstc->rcdev = rcdev;
+        rstc->id = rstc_id;
+
+        return rstc;
+}
+EXPORT_SYMBOL_GPL(reset_control_get);
+
+/**
+ * reset_control_put - free the reset controller
+ * @rstc: reset controller
+ */
+
+void reset_control_put(struct reset_control *rstc)
+{
+        if (IS_ERR(rstc))
+                return;
+
+        module_put(rstc->rcdev->owner);
+        kfree(rstc);
+}
+EXPORT_SYMBOL_GPL(reset_control_put);
+
+static void devm_reset_control_release(struct device *dev, void *res)
+{
+        reset_control_put(*(struct reset_control **)res);
+}
+
+/**
+ * devm_reset_control_get - resource managed reset_control_get()
+ * @dev: device to be reset by the controller
+ * @id: reset line name
+ *
+ * Managed reset_control_get(). For reset controllers returned from this
+ * function, reset_control_put() is called automatically on driver detach.
+ * See reset_control_get() for more information.
+ */
+struct reset_control *devm_reset_control_get(struct device *dev, const char *id)
+{
+        struct reset_control **ptr, *rstc;
+
+        ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
+                           GFP_KERNEL);
+        if (!ptr)
+                return ERR_PTR(-ENOMEM);
+
+        rstc = reset_control_get(dev, id);
+        if (!IS_ERR(rstc)) {
+                *ptr = rstc;
+                devres_add(dev, ptr);
+        } else {
+                devres_free(ptr);
+        }
+
+        return rstc;
+}
+EXPORT_SYMBOL_GPL(devm_reset_control_get);
+
+static int devm_reset_control_match(struct device *dev, void *res, void *data)
+{
+        struct reset_control **rstc = res;
+        if (WARN_ON(!rstc || !*rstc))
+                return 0;
+        return *rstc == data;
+}
+
+/**
+ * devm_reset_control_put - resource managed reset_control_put()
+ * @rstc: reset controller to free
+ *
+ * Deallocate a reset control allocated withd devm_reset_control_get().
+ * This function will not need to be called normally, as devres will take
+ * care of freeing the resource.
+ */
+void devm_reset_control_put(struct reset_control *rstc)
+{
+        int ret;
+
+        ret = devres_release(rstc->dev, devm_reset_control_release,
+                             devm_reset_control_match, rstc);
+        if (ret)
+                WARN_ON(ret);
+}
+EXPORT_SYMBOL_GPL(devm_reset_control_put);
+
+/**
+ * device_reset - find reset controller associated with the device
+ *                and perform reset
+ * @dev: device to be reset by the controller
+ *
+ * Convenience wrapper for reset_control_get() and reset_control_reset().
+ * This is useful for the common case of devices with single, dedicated reset
+ * lines.
+ */
+int device_reset(struct device *dev)
+{
+        struct reset_control *rstc;
+        int ret;
+
+        rstc = reset_control_get(dev, NULL);
+        if (IS_ERR(rstc))
+                return PTR_ERR(rstc);
+
+        ret = reset_control_reset(rstc);
+
+        reset_control_put(rstc);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(device_reset);