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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
*/
#include <linux/crc32.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/of_reserved_mem.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
struct rmem {
struct device *dev;
struct nvmem_device *nvmem;
struct reserved_mem *mem;
};
struct rmem_match_data {
int (*checksum)(struct rmem *priv);
};
struct __packed rmem_eyeq5_header {
u32 magic;
u32 version;
u32 size;
};
#define RMEM_EYEQ5_MAGIC ((u32)0xDABBAD00)
static int rmem_read(void *context, unsigned int offset,
void *val, size_t bytes)
{
struct rmem *priv = context;
void *addr;
if ((phys_addr_t)offset + bytes > priv->mem->size)
return -EIO;
/*
* 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, priv->mem->size, MEMREMAP_WB);
if (!addr) {
dev_err(priv->dev, "Failed to remap memory region\n");
return -ENOMEM;
}
memcpy(val, addr + offset, bytes);
memunmap(addr);
return 0;
}
static int rmem_eyeq5_checksum(struct rmem *priv)
{
void *buf __free(kfree) = NULL;
struct rmem_eyeq5_header header;
u32 computed_crc, *target_crc;
size_t data_size;
int ret;
ret = rmem_read(priv, 0, &header, sizeof(header));
if (ret)
return ret;
if (header.magic != RMEM_EYEQ5_MAGIC)
return -EINVAL;
/*
* Avoid massive kmalloc() if header read is invalid;
* the check would be done by the next rmem_read() anyway.
*/
if (header.size > priv->mem->size)
return -EINVAL;
/*
* 0 +-------------------+
* | Header (12 bytes) | \
* +-------------------+ |
* | | | data to be CRCed
* | ... | |
* | | /
* data_size +-------------------+
* | CRC (4 bytes) |
* header.size +-------------------+
*/
buf = kmalloc(header.size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
ret = rmem_read(priv, 0, buf, header.size);
if (ret)
return ret;
data_size = header.size - sizeof(*target_crc);
target_crc = buf + data_size;
computed_crc = crc32(U32_MAX, buf, data_size) ^ U32_MAX;
if (computed_crc == *target_crc)
return 0;
dev_err(priv->dev,
"checksum failed: computed %#x, expected %#x, header (%#x, %#x, %#x)\n",
computed_crc, *target_crc, header.magic, header.version, header.size);
return -EINVAL;
}
static int rmem_probe(struct platform_device *pdev)
{
struct nvmem_config config = { };
struct device *dev = &pdev->dev;
const struct rmem_match_data *match_data = device_get_match_data(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.id = NVMEM_DEVID_AUTO;
config.size = mem->size;
config.reg_read = rmem_read;
if (match_data && match_data->checksum) {
int ret = match_data->checksum(priv);
if (ret)
return ret;
}
return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
}
static const struct rmem_match_data rmem_eyeq5_match_data = {
.checksum = rmem_eyeq5_checksum,
};
static const struct of_device_id rmem_match[] = {
{ .compatible = "mobileye,eyeq5-bootloader-config", .data = &rmem_eyeq5_match_data },
{ .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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