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1// SPDX-License-Identifier: GPL-2.0+2/*3 * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>4 */5 6#include <linux/io.h>7#include <linux/module.h>8#include <linux/nvmem-provider.h>9#include <linux/of_reserved_mem.h>10#include <linux/platform_device.h>11 12struct rmem {13 struct device *dev;14 struct nvmem_device *nvmem;15 struct reserved_mem *mem;16 17 phys_addr_t size;18};19 20static int rmem_read(void *context, unsigned int offset,21 void *val, size_t bytes)22{23 struct rmem *priv = context;24 size_t available = priv->mem->size;25 loff_t off = offset;26 void *addr;27 int count;28 29 /*30 * Only map the reserved memory at this point to avoid potential rogue31 * kernel threads inadvertently modifying it. Based on the current32 * uses-cases for this driver, the performance hit isn't a concern.33 * Nor is likely to be, given the nature of the subsystem. Most nvmem34 * devices operate over slow buses to begin with.35 *36 * An alternative would be setting the memory as RO, set_memory_ro(),37 * but as of Dec 2020 this isn't possible on arm64.38 */39 addr = memremap(priv->mem->base, available, MEMREMAP_WB);40 if (!addr) {41 dev_err(priv->dev, "Failed to remap memory region\n");42 return -ENOMEM;43 }44 45 count = memory_read_from_buffer(val, bytes, &off, addr, available);46 47 memunmap(addr);48 49 if (count < 0)50 return count;51 52 return count == bytes ? 0 : -EIO;53}54 55static int rmem_probe(struct platform_device *pdev)56{57 struct nvmem_config config = { };58 struct device *dev = &pdev->dev;59 struct reserved_mem *mem;60 struct rmem *priv;61 62 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);63 if (!priv)64 return -ENOMEM;65 priv->dev = dev;66 67 mem = of_reserved_mem_lookup(dev->of_node);68 if (!mem) {69 dev_err(dev, "Failed to lookup reserved memory\n");70 return -EINVAL;71 }72 priv->mem = mem;73 74 config.dev = dev;75 config.priv = priv;76 config.name = "rmem";77 config.id = NVMEM_DEVID_AUTO;78 config.size = mem->size;79 config.reg_read = rmem_read;80 81 return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));82}83 84static const struct of_device_id rmem_match[] = {85 { .compatible = "nvmem-rmem", },86 { /* sentinel */ },87};88MODULE_DEVICE_TABLE(of, rmem_match);89 90static struct platform_driver rmem_driver = {91 .probe = rmem_probe,92 .driver = {93 .name = "rmem",94 .of_match_table = rmem_match,95 },96};97module_platform_driver(rmem_driver);98 99MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");100MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");101MODULE_LICENSE("GPL");102