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97 lines
2.3 KiB
97 lines
2.3 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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/* |
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* Copyright (C) 2020 Nicolas Saenz Julienne <[email protected]> |
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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 (IS_ERR(addr)) { |
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dev_err(priv->dev, "Failed to remap memory region\n"); |
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return PTR_ERR(addr); |
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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 <[email protected]>"); |
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MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver"); |
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MODULE_LICENSE("GPL");
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