nvmem: Add a simple NVMEM framework for nvmem providers

This patch adds just providers part of the framework just to enable easy
review.

Up until now, NVMEM drivers like eeprom were stored in drivers/misc,
where they all had to duplicate pretty much the same code to register
a sysfs file, allow in-kernel users to access the content of the devices
they were driving, etc.

This was also a problem as far as other in-kernel users were involved,
since the solutions used were pretty much different from on driver to
another, there was a rather big abstraction leak.

This introduction of this framework aims at solving this. It also
introduces DT representation for consumer devices to go get the data
they require (MAC Addresses, SoC/Revision ID, part numbers, and so on)
from the nvmems.

Having regmap interface to this framework would give much better
abstraction for nvmems on different buses.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
[Maxime Ripard: intial version of eeprom framework]
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 425 insertions, 0 deletions

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
new file mode 100644
index 000000000000..de90c82d891b
--- /dev/null
+++ b/drivers/nvmem/Kconfig
@@ -0,0 +1,13 @@
+menuconfig NVMEM
+        tristate "NVMEM Support"
+        select REGMAP
+        help
+          Support for NVMEM(Non Volatile Memory) devices like EEPROM, EFUSES...
+
+          This framework is designed to provide a generic interface to NVMEM
+          from both the Linux Kernel and the userspace.
+
+          This driver can also be built as a module. If so, the module
+          will be called nvmem_core.
+
+          If unsure, say no.
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
new file mode 100644
index 000000000000..6df2c6952ad5
--- /dev/null
+++ b/drivers/nvmem/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for nvmem drivers.
+#
+
+obj-$(CONFIG_NVMEM)             += nvmem_core.o
+nvmem_core-y                    := core.o
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
new file mode 100644
index 000000000000..2b024915e224
--- /dev/null
+++ b/drivers/nvmem/core.c
@@ -0,0 +1,406 @@
+/*
+ * nvmem framework core.
+ *
+ * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
+ * Copyright (C) 2013 Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+struct nvmem_device {
+        const char              *name;
+        struct regmap           *regmap;
+        struct module           *owner;
+        struct device           dev;
+        int                     stride;
+        int                     word_size;
+        int                     ncells;
+        int                     id;
+        int                     users;
+        size_t                  size;
+        bool                    read_only;
+};
+
+struct nvmem_cell {
+        const char              *name;
+        int                     offset;
+        int                     bytes;
+        int                     bit_offset;
+        int                     nbits;
+        struct nvmem_device     *nvmem;
+        struct list_head        node;
+};
+
+static DEFINE_MUTEX(nvmem_mutex);
+static DEFINE_IDA(nvmem_ida);
+
+static LIST_HEAD(nvmem_cells);
+static DEFINE_MUTEX(nvmem_cells_mutex);
+
+#define to_nvmem_device(d) container_of(d, struct nvmem_device, dev)
+
+static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
+                                    struct bin_attribute *attr,
+                                    char *buf, loff_t pos, size_t count)
+{
+        struct device *dev = container_of(kobj, struct device, kobj);
+        struct nvmem_device *nvmem = to_nvmem_device(dev);
+        int rc;
+
+        /* Stop the user from reading */
+        if (pos > nvmem->size)
+                return 0;
+
+        if (pos + count > nvmem->size)
+                count = nvmem->size - pos;
+
+        count = round_down(count, nvmem->word_size);
+
+        rc = regmap_raw_read(nvmem->regmap, pos, buf, count);
+
+        if (IS_ERR_VALUE(rc))
+                return rc;
+
+        return count;
+}
+
+static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
+                                     struct bin_attribute *attr,
+                                     char *buf, loff_t pos, size_t count)
+{
+        struct device *dev = container_of(kobj, struct device, kobj);
+        struct nvmem_device *nvmem = to_nvmem_device(dev);
+        int rc;
+
+        /* Stop the user from writing */
+        if (pos > nvmem->size)
+                return 0;
+
+        if (pos + count > nvmem->size)
+                count = nvmem->size - pos;
+
+        count = round_down(count, nvmem->word_size);
+
+        rc = regmap_raw_write(nvmem->regmap, pos, buf, count);
+
+        if (IS_ERR_VALUE(rc))
+                return rc;
+
+        return count;
+}
+
+/* default read/write permissions */
+static struct bin_attribute bin_attr_rw_nvmem = {
+        .attr   = {
+                .name   = "nvmem",
+                .mode   = S_IWUSR | S_IRUGO,
+        },
+        .read   = bin_attr_nvmem_read,
+        .write  = bin_attr_nvmem_write,
+};
+
+static struct bin_attribute *nvmem_bin_rw_attributes[] = {
+        &bin_attr_rw_nvmem,
+        NULL,
+};
+
+static const struct attribute_group nvmem_bin_rw_group = {
+        .bin_attrs      = nvmem_bin_rw_attributes,
+};
+
+static const struct attribute_group *nvmem_rw_dev_groups[] = {
+        &nvmem_bin_rw_group,
+        NULL,
+};
+
+/* read only permission */
+static struct bin_attribute bin_attr_ro_nvmem = {
+        .attr   = {
+                .name   = "nvmem",
+                .mode   = S_IRUGO,
+        },
+        .read   = bin_attr_nvmem_read,
+};
+
+static struct bin_attribute *nvmem_bin_ro_attributes[] = {
+        &bin_attr_ro_nvmem,
+        NULL,
+};
+
+static const struct attribute_group nvmem_bin_ro_group = {
+        .bin_attrs      = nvmem_bin_ro_attributes,
+};
+
+static const struct attribute_group *nvmem_ro_dev_groups[] = {
+        &nvmem_bin_ro_group,
+        NULL,
+};
+
+static void nvmem_release(struct device *dev)
+{
+        struct nvmem_device *nvmem = to_nvmem_device(dev);
+
+        ida_simple_remove(&nvmem_ida, nvmem->id);
+        kfree(nvmem);
+}
+
+static const struct device_type nvmem_provider_type = {
+        .release        = nvmem_release,
+};
+
+static struct bus_type nvmem_bus_type = {
+        .name           = "nvmem",
+};
+
+static int of_nvmem_match(struct device *dev, void *nvmem_np)
+{
+        return dev->of_node == nvmem_np;
+}
+
+static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)
+{
+        struct device *d;
+
+        if (!nvmem_np)
+                return NULL;
+
+        d = bus_find_device(&nvmem_bus_type, NULL, nvmem_np, of_nvmem_match);
+
+        if (!d)
+                return NULL;
+
+        return to_nvmem_device(d);
+}
+
+static struct nvmem_cell *nvmem_find_cell(const char *cell_id)
+{
+        struct nvmem_cell *p;
+
+        list_for_each_entry(p, &nvmem_cells, node)
+                if (p && !strcmp(p->name, cell_id))
+                        return p;
+
+        return NULL;
+}
+
+static void nvmem_cell_drop(struct nvmem_cell *cell)
+{
+        mutex_lock(&nvmem_cells_mutex);
+        list_del(&cell->node);
+        mutex_unlock(&nvmem_cells_mutex);
+        kfree(cell);
+}
+
+static void nvmem_device_remove_all_cells(const struct nvmem_device *nvmem)
+{
+        struct nvmem_cell *cell;
+        struct list_head *p, *n;
+
+        list_for_each_safe(p, n, &nvmem_cells) {
+                cell = list_entry(p, struct nvmem_cell, node);
+                if (cell->nvmem == nvmem)
+                        nvmem_cell_drop(cell);
+        }
+}
+
+static void nvmem_cell_add(struct nvmem_cell *cell)
+{
+        mutex_lock(&nvmem_cells_mutex);
+        list_add_tail(&cell->node, &nvmem_cells);
+        mutex_unlock(&nvmem_cells_mutex);
+}
+
+static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
+                                   const struct nvmem_cell_info *info,
+                                   struct nvmem_cell *cell)
+{
+        cell->nvmem = nvmem;
+        cell->offset = info->offset;
+        cell->bytes = info->bytes;
+        cell->name = info->name;
+
+        cell->bit_offset = info->bit_offset;
+        cell->nbits = info->nbits;
+
+        if (cell->nbits)
+                cell->bytes = DIV_ROUND_UP(cell->nbits + cell->bit_offset,
+                                           BITS_PER_BYTE);
+
+        if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
+                dev_err(&nvmem->dev,
+                        "cell %s unaligned to nvmem stride %d\n",
+                        cell->name, nvmem->stride);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+static int nvmem_add_cells(struct nvmem_device *nvmem,
+                           const struct nvmem_config *cfg)
+{
+        struct nvmem_cell **cells;
+        const struct nvmem_cell_info *info = cfg->cells;
+        int i, rval;
+
+        cells = kcalloc(cfg->ncells, sizeof(*cells), GFP_KERNEL);
+        if (!cells)
+                return -ENOMEM;
+
+        for (i = 0; i < cfg->ncells; i++) {
+                cells[i] = kzalloc(sizeof(**cells), GFP_KERNEL);
+                if (!cells[i]) {
+                        rval = -ENOMEM;
+                        goto err;
+                }
+
+                rval = nvmem_cell_info_to_nvmem_cell(nvmem, &info[i], cells[i]);
+                if (IS_ERR_VALUE(rval)) {
+                        kfree(cells[i]);
+                        goto err;
+                }
+
+                nvmem_cell_add(cells[i]);
+        }
+
+        nvmem->ncells = cfg->ncells;
+        /* remove tmp array */
+        kfree(cells);
+
+        return 0;
+err:
+        while (--i)
+                nvmem_cell_drop(cells[i]);
+
+        return rval;
+}
+
+/**
+ * nvmem_register() - Register a nvmem device for given nvmem_config.
+ * Also creates an binary entry in /sys/bus/nvmem/devices/dev-name/nvmem
+ *
+ * @config: nvmem device configuration with which nvmem device is created.
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer to nvmem_device
+ * on success.
+ */
+
+struct nvmem_device *nvmem_register(const struct nvmem_config *config)
+{
+        struct nvmem_device *nvmem;
+        struct device_node *np;
+        struct regmap *rm;
+        int rval;
+
+        if (!config->dev)
+                return ERR_PTR(-EINVAL);
+
+        rm = dev_get_regmap(config->dev, NULL);
+        if (!rm) {
+                dev_err(config->dev, "Regmap not found\n");
+                return ERR_PTR(-EINVAL);
+        }
+
+        nvmem = kzalloc(sizeof(*nvmem), GFP_KERNEL);
+        if (!nvmem)
+                return ERR_PTR(-ENOMEM);
+
+        rval  = ida_simple_get(&nvmem_ida, 0, 0, GFP_KERNEL);
+        if (rval < 0) {
+                kfree(nvmem);
+                return ERR_PTR(rval);
+        }
+
+        nvmem->id = rval;
+        nvmem->regmap = rm;
+        nvmem->owner = config->owner;
+        nvmem->stride = regmap_get_reg_stride(rm);
+        nvmem->word_size = regmap_get_val_bytes(rm);
+        nvmem->size = regmap_get_max_register(rm) + nvmem->stride;
+        nvmem->dev.type = &nvmem_provider_type;
+        nvmem->dev.bus = &nvmem_bus_type;
+        nvmem->dev.parent = config->dev;
+        np = config->dev->of_node;
+        nvmem->dev.of_node = np;
+        dev_set_name(&nvmem->dev, "%s%d",
+                     config->name ? : "nvmem", config->id);
+
+        nvmem->read_only = of_property_read_bool(np, "read-only") |
+                           config->read_only;
+
+        nvmem->dev.groups = nvmem->read_only ? nvmem_ro_dev_groups :
+                                               nvmem_rw_dev_groups;
+
+        device_initialize(&nvmem->dev);
+
+        dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
+
+        rval = device_add(&nvmem->dev);
+        if (rval) {
+                ida_simple_remove(&nvmem_ida, nvmem->id);
+                kfree(nvmem);
+                return ERR_PTR(rval);
+        }
+
+        if (config->cells)
+                nvmem_add_cells(nvmem, config);
+
+        return nvmem;
+}
+EXPORT_SYMBOL_GPL(nvmem_register);
+
+/**
+ * nvmem_unregister() - Unregister previously registered nvmem device
+ *
+ * @nvmem: Pointer to previously registered nvmem device.
+ *
+ * Return: Will be an negative on error or a zero on success.
+ */
+int nvmem_unregister(struct nvmem_device *nvmem)
+{
+        if (nvmem->users)
+                return -EBUSY;
+
+        nvmem_device_remove_all_cells(nvmem);
+        device_del(&nvmem->dev);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(nvmem_unregister);
+
+static int __init nvmem_init(void)
+{
+        return bus_register(&nvmem_bus_type);
+}
+
+static void __exit nvmem_exit(void)
+{
+        bus_unregister(&nvmem_bus_type);
+}
+
+subsys_initcall(nvmem_init);
+module_exit(nvmem_exit);
+
+MODULE_AUTHOR("Srinivas Kandagatla <srinivas.kandagatla@linaro.org");
+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com");
+MODULE_DESCRIPTION("nvmem Driver Core");
+MODULE_LICENSE("GPL v2");