// 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");