[linux.git] / drivers / nvmem / rmem.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2020 Nicolas Saenz Julienne <[email protected]>
 */

#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 (IS_ERR(addr)) {
		dev_err(priv->dev, "Failed to remap memory region\n");
		return PTR_ERR(addr);
	}

	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 <[email protected]>");
MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
5a3fa75a NSJ	1	// SPDX-License-Identifier: GPL-2.0+
	2	/*
	3	* Copyright (C) 2020 Nicolas Saenz Julienne <[email protected]>
	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
	12	struct rmem {
	13	struct device *dev;
	14	struct nvmem_device *nvmem;
	15	struct reserved_mem *mem;
	16
	17	phys_addr_t size;
	18	};
	19
	20	static 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 rogue
	31	* kernel threads inadvertently modifying it. Based on the current
	32	* 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 nvmem
	34	* 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 (IS_ERR(addr)) {
	41	dev_err(priv->dev, "Failed to remap memory region\n");
	42	return PTR_ERR(addr);
	43	}
	44
	45	count = memory_read_from_buffer(val, bytes, &off, addr, available);
	46
	47	memunmap(addr);
	48
	49	return count;
	50	}
	51
	52	static int rmem_probe(struct platform_device *pdev)
	53	{
	54	struct nvmem_config config = { };
	55	struct device *dev = &pdev->dev;
	56	struct reserved_mem *mem;
	57	struct rmem *priv;
	58
	59	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	60	if (!priv)
	61	return -ENOMEM;
	62	priv->dev = dev;
	63
	64	mem = of_reserved_mem_lookup(dev->of_node);
65	if (!mem) {
66	dev_err(dev, "Failed to lookup reserved memory\n");
67	return -EINVAL;
68	}
69	priv->mem = mem;
70
71	config.dev = dev;
72	config.priv = priv;
73	config.name = "rmem";
74	config.size = mem->size;
75	config.reg_read = rmem_read;
76
77	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
78	}
79
80	static const struct of_device_id rmem_match[] = {
81	{ .compatible = "nvmem-rmem", },
82	{ /* sentinel */ },
83	};
84	MODULE_DEVICE_TABLE(of, rmem_match);
85
86	static struct platform_driver rmem_driver = {
87	.probe = rmem_probe,
88	.driver = {
89	.name = "rmem",
90	.of_match_table = rmem_match,
91	},
92	};
93	module_platform_driver(rmem_driver);
94
95	MODULE_AUTHOR("Nicolas Saenz Julienne <[email protected]>");
96	MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
97	MODULE_LICENSE("GPL");