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 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 (!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");

 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 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 (!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	return count;
 
 
 
50}
51
52static 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.id = NVMEM_DEVID_AUTO;
75	config.size = mem->size;
76	config.reg_read = rmem_read;
77
78	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
79}
80
81static const struct of_device_id rmem_match[] = {
82	{ .compatible = "nvmem-rmem", },
83	{ /* sentinel */ },
84};
85MODULE_DEVICE_TABLE(of, rmem_match);
86
87static struct platform_driver rmem_driver = {
88	.probe = rmem_probe,
89	.driver = {
90		.name = "rmem",
91		.of_match_table = rmem_match,
92	},
93};
94module_platform_driver(rmem_driver);
95
96MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
97MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
98MODULE_LICENSE("GPL");