diff options
Diffstat (limited to 'drivers/nvmem/rmem.c')
| -rw-r--r-- | drivers/nvmem/rmem.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/drivers/nvmem/rmem.c b/drivers/nvmem/rmem.c new file mode 100644 index 000000000000..b39d628cb60a --- /dev/null +++ b/drivers/nvmem/rmem.c @@ -0,0 +1,178 @@ +// 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"); |