1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
7 #include <linux/module.h>
8 #include <linux/nvmem-provider.h>
9 #include <linux/of_reserved_mem.h>
10 #include <linux/platform_device.h>
14 struct nvmem_device
*nvmem
;
15 struct reserved_mem
*mem
;
20 static int rmem_read(void *context
, unsigned int offset
,
21 void *val
, size_t bytes
)
23 struct rmem
*priv
= context
;
24 size_t available
= priv
->mem
->size
;
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.
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.
39 addr
= memremap(priv
->mem
->base
, available
, MEMREMAP_WB
);
41 dev_err(priv
->dev
, "Failed to remap memory region\n");
45 count
= memory_read_from_buffer(val
, bytes
, &off
, addr
, available
);
52 static int rmem_probe(struct platform_device
*pdev
)
54 struct nvmem_config config
= { };
55 struct device
*dev
= &pdev
->dev
;
56 struct reserved_mem
*mem
;
59 priv
= devm_kzalloc(dev
, sizeof(*priv
), GFP_KERNEL
);
64 mem
= of_reserved_mem_lookup(dev
->of_node
);
66 dev_err(dev
, "Failed to lookup reserved memory\n");
74 config
.size
= mem
->size
;
75 config
.reg_read
= rmem_read
;
77 return PTR_ERR_OR_ZERO(devm_nvmem_register(dev
, &config
));
80 static const struct of_device_id rmem_match
[] = {
81 { .compatible
= "nvmem-rmem", },
84 MODULE_DEVICE_TABLE(of
, rmem_match
);
86 static struct platform_driver rmem_driver
= {
90 .of_match_table
= rmem_match
,
93 module_platform_driver(rmem_driver
);
95 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
96 MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
97 MODULE_LICENSE("GPL");