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