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  */
41 static 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 
70 struct litex_soc_ctrl_device {
71 	void __iomem *base;
72 	struct notifier_block reset_nb;
73 };
74 
75 static 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
86 static const struct of_device_id litex_soc_ctrl_of_match[] = {
87 	{.compatible = "litex,soc-controller"},
88 	{},
89 };
90 MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
91 #endif /* CONFIG_OF */
92 
93 static 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 
123 static int 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 	return 0;
129 }
130 
131 static struct platform_driver litex_soc_ctrl_driver = {
132 	.driver = {
133 		.name = "litex-soc-controller",
134 		.of_match_table = of_match_ptr(litex_soc_ctrl_of_match)
135 	},
136 	.probe = litex_soc_ctrl_probe,
137 	.remove = litex_soc_ctrl_remove,
138 };
139 
140 module_platform_driver(litex_soc_ctrl_driver);
141 MODULE_DESCRIPTION("LiteX SoC Controller driver");
142 MODULE_AUTHOR("Antmicro <www.antmicro.com>");
143 MODULE_LICENSE("GPL v2");
144