1// SPDX-License-Identifier: GPL-2.0
2/*
3 * LiteX SoC Controller Driver
4 *
5 * Copyright (C) 2020 Antmicro <www.antmicro.com>
6 *
7 */
8
9#include <linux/litex.h>
10#include <linux/device.h>
11#include <linux/errno.h>
12#include <linux/of.h>
13#include <linux/platform_device.h>
14#include <linux/printk.h>
15#include <linux/module.h>
16#include <linux/io.h>
17#include <linux/reboot.h>
18
19/* reset register located at the base address */
20#define RESET_REG_OFF           0x00
21#define RESET_REG_VALUE         0x00000001
22
23#define SCRATCH_REG_OFF         0x04
24#define SCRATCH_REG_VALUE       0x12345678
25#define SCRATCH_TEST_VALUE      0xdeadbeef
26
27/*
28 * Check LiteX CSR read/write access
29 *
30 * This function reads and writes a scratch register in order to verify if CSR
31 * access works.
32 *
33 * In case any problems are detected, the driver should panic.
34 *
35 * Access to the LiteX CSR is, by design, done in CPU native endianness.
36 * The driver should not dynamically configure access functions when
37 * the endianness mismatch is detected. Such situation indicates problems in
38 * the soft SoC design and should be solved at the LiteX generator level,
39 * not in the software.
40 */
41static int litex_check_csr_access(void __iomem *reg_addr)
42{
43	unsigned long reg;
44
45	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
46
47	if (reg != SCRATCH_REG_VALUE) {
48		panic("Scratch register read error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
49			SCRATCH_REG_VALUE, reg);
50		return -EINVAL;
51	}
52
53	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_TEST_VALUE);
54	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
55
56	if (reg != SCRATCH_TEST_VALUE) {
57		panic("Scratch register write error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
58			SCRATCH_TEST_VALUE, reg);
59		return -EINVAL;
60	}
61
62	/* restore original value of the SCRATCH register */
63	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_VALUE);
64
65	pr_info("LiteX SoC Controller driver initialized");
66
67	return 0;
68}
69
70struct litex_soc_ctrl_device {
71	void __iomem *base;
72	struct notifier_block reset_nb;
73};
74
75static int litex_reset_handler(struct notifier_block *this, unsigned long mode,
76			       void *cmd)
77{
78	struct litex_soc_ctrl_device *soc_ctrl_dev =
79		container_of(this, struct litex_soc_ctrl_device, reset_nb);
80
81	litex_write32(soc_ctrl_dev->base + RESET_REG_OFF, RESET_REG_VALUE);
82	return NOTIFY_DONE;
83}
84
85#ifdef CONFIG_OF
86static const struct of_device_id litex_soc_ctrl_of_match[] = {
87	{.compatible = "litex,soc-controller"},
88	{},
89};
90MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
91#endif /* CONFIG_OF */
92
93static int litex_soc_ctrl_probe(struct platform_device *pdev)
94{
95	struct litex_soc_ctrl_device *soc_ctrl_dev;
96	int error;
97
98	soc_ctrl_dev = devm_kzalloc(&pdev->dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
99	if (!soc_ctrl_dev)
100		return -ENOMEM;
101
102	soc_ctrl_dev->base = devm_platform_ioremap_resource(pdev, 0);
103	if (IS_ERR(soc_ctrl_dev->base))
104		return PTR_ERR(soc_ctrl_dev->base);
105
106	error = litex_check_csr_access(soc_ctrl_dev->base);
107	if (error)
108		return error;
109
110	platform_set_drvdata(pdev, soc_ctrl_dev);
111
112	soc_ctrl_dev->reset_nb.notifier_call = litex_reset_handler;
113	soc_ctrl_dev->reset_nb.priority = 128;
114	error = register_restart_handler(&soc_ctrl_dev->reset_nb);
115	if (error) {
116		dev_warn(&pdev->dev, "cannot register restart handler: %d\n",
117			 error);
118	}
119
120	return 0;
121}
122
123static void litex_soc_ctrl_remove(struct platform_device *pdev)
124{
125	struct litex_soc_ctrl_device *soc_ctrl_dev = platform_get_drvdata(pdev);
126
127	unregister_restart_handler(&soc_ctrl_dev->reset_nb);
128}
129
130static struct platform_driver litex_soc_ctrl_driver = {
131	.driver = {
132		.name = "litex-soc-controller",
133		.of_match_table = of_match_ptr(litex_soc_ctrl_of_match)
134	},
135	.probe = litex_soc_ctrl_probe,
136	.remove_new = litex_soc_ctrl_remove,
137};
138
139module_platform_driver(litex_soc_ctrl_driver);
140MODULE_DESCRIPTION("LiteX SoC Controller driver");
141MODULE_AUTHOR("Antmicro <www.antmicro.com>");
142MODULE_LICENSE("GPL v2");
143