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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
*/
#include <linux/io.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/of_reserved_mem.h>
#include <linux/platform_device.h>
struct rmem {
struct device *dev;
struct nvmem_device *nvmem;
struct reserved_mem *mem;
phys_addr_t size;
};
static int rmem_read(void *context, unsigned int offset,
void *val, size_t bytes)
{
struct rmem *priv = context;
size_t available = priv->mem->size;
loff_t off = offset;
void *addr;
int count;
/*
* Only map the reserved memory at this point to avoid potential rogue
* kernel threads inadvertently modifying it. Based on the current
* uses-cases for this driver, the performance hit isn't a concern.
* Nor is likely to be, given the nature of the subsystem. Most nvmem
* devices operate over slow buses to begin with.
*
* An alternative would be setting the memory as RO, set_memory_ro(),
* but as of Dec 2020 this isn't possible on arm64.
*/
addr = memremap(priv->mem->base, available, MEMREMAP_WB);
if (!addr) {
dev_err(priv->dev, "Failed to remap memory region\n");
return -ENOMEM;
}
count = memory_read_from_buffer(val, bytes, &off, addr, available);
memunmap(addr);
return count;
}
static int rmem_probe(struct platform_device *pdev)
{
struct nvmem_config config = { };
struct device *dev = &pdev->dev;
struct reserved_mem *mem;
struct rmem *priv;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->dev = dev;
mem = of_reserved_mem_lookup(dev->of_node);
if (!mem) {
dev_err(dev, "Failed to lookup reserved memory\n");
return -EINVAL;
}
priv->mem = mem;
config.dev = dev;
config.priv = priv;
config.name = "rmem";
config.size = mem->size;
config.reg_read = rmem_read;
return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
}
static const struct of_device_id rmem_match[] = {
{ .compatible = "nvmem-rmem", },
{ /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, rmem_match);
static struct platform_driver rmem_driver = {
.probe = rmem_probe,
.driver = {
.name = "rmem",
.of_match_table = rmem_match,
},
};
module_platform_driver(rmem_driver);
MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
MODULE_LICENSE("GPL");
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