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: reg_addr + SCRATCH_REG_OFF);
46
47 if (reg != SCRATCH_REG_VALUE) {
48 panic(fmt: "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: reg_addr + SCRATCH_REG_OFF, SCRATCH_TEST_VALUE);
54 reg = litex_read32(reg: reg_addr + SCRATCH_REG_OFF);
55
56 if (reg != SCRATCH_TEST_VALUE) {
57 panic(fmt: "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: 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(reg: 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(dev: &pdev->dev, size: 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, index: 0);
103 if (IS_ERR(ptr: soc_ctrl_dev->base))
104 return PTR_ERR(ptr: soc_ctrl_dev->base);
105
106 error = litex_check_csr_access(reg_addr: soc_ctrl_dev->base);
107 if (error)
108 return error;
109
110 platform_set_drvdata(pdev, data: 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

source code of linux/drivers/soc/litex/litex_soc_ctrl.c