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/errno.h>
17 #include <linux/io.h>
18 #include <linux/reboot.h>
19 
20 /* reset register located at the base address */
21 #define RESET_REG_OFF           0x00
22 #define RESET_REG_VALUE         0x00000001
23 
24 #define SCRATCH_REG_OFF         0x04
25 #define SCRATCH_REG_VALUE       0x12345678
26 #define SCRATCH_TEST_VALUE      0xdeadbeef
27 
28 /*
29  * Check LiteX CSR read/write access
30  *
31  * This function reads and writes a scratch register in order to verify if CSR
32  * access works.
33  *
34  * In case any problems are detected, the driver should panic.
35  *
36  * Access to the LiteX CSR is, by design, done in CPU native endianness.
37  * The driver should not dynamically configure access functions when
38  * the endianness mismatch is detected. Such situation indicates problems in
39  * the soft SoC design and should be solved at the LiteX generator level,
40  * not in the software.
41  */
42 static int litex_check_csr_access(void __iomem *reg_addr)
43 {
44 	unsigned long reg;
45 
46 	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
47 
48 	if (reg != SCRATCH_REG_VALUE) {
49 		panic("Scratch register read error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
50 			SCRATCH_REG_VALUE, reg);
51 		return -EINVAL;
52 	}
53 
54 	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_TEST_VALUE);
55 	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
56 
57 	if (reg != SCRATCH_TEST_VALUE) {
58 		panic("Scratch register write error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
59 			SCRATCH_TEST_VALUE, reg);
60 		return -EINVAL;
61 	}
62 
63 	/* restore original value of the SCRATCH register */
64 	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_VALUE);
65 
66 	pr_info("LiteX SoC Controller driver initialized: subreg:%d, align:%d",
67 		LITEX_SUBREG_SIZE, LITEX_SUBREG_ALIGN);
68 
69 	return 0;
70 }
71 
72 struct litex_soc_ctrl_device {
73 	void __iomem *base;
74 	struct notifier_block reset_nb;
75 };
76 
77 static int litex_reset_handler(struct notifier_block *this, unsigned long mode,
78 			       void *cmd)
79 {
80 	struct litex_soc_ctrl_device *soc_ctrl_dev =
81 		container_of(this, struct litex_soc_ctrl_device, reset_nb);
82 
83 	litex_write32(soc_ctrl_dev->base + RESET_REG_OFF, RESET_REG_VALUE);
84 	return NOTIFY_DONE;
85 }
86 
87 #ifdef CONFIG_OF
88 static const struct of_device_id litex_soc_ctrl_of_match[] = {
89 	{.compatible = "litex,soc-controller"},
90 	{},
91 };
92 MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
93 #endif /* CONFIG_OF */
94 
95 static int litex_soc_ctrl_probe(struct platform_device *pdev)
96 {
97 	struct litex_soc_ctrl_device *soc_ctrl_dev;
98 	int error;
99 
100 	soc_ctrl_dev = devm_kzalloc(&pdev->dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
101 	if (!soc_ctrl_dev)
102 		return -ENOMEM;
103 
104 	soc_ctrl_dev->base = devm_platform_ioremap_resource(pdev, 0);
105 	if (IS_ERR(soc_ctrl_dev->base))
106 		return PTR_ERR(soc_ctrl_dev->base);
107 
108 	error = litex_check_csr_access(soc_ctrl_dev->base);
109 	if (error)
110 		return error;
111 
112 	platform_set_drvdata(pdev, soc_ctrl_dev);
113 
114 	soc_ctrl_dev->reset_nb.notifier_call = litex_reset_handler;
115 	soc_ctrl_dev->reset_nb.priority = 128;
116 	error = register_restart_handler(&soc_ctrl_dev->reset_nb);
117 	if (error) {
118 		dev_warn(&pdev->dev, "cannot register restart handler: %d\n",
119 			 error);
120 	}
121 
122 	return 0;
123 }
124 
125 static int litex_soc_ctrl_remove(struct platform_device *pdev)
126 {
127 	struct litex_soc_ctrl_device *soc_ctrl_dev = platform_get_drvdata(pdev);
128 
129 	unregister_restart_handler(&soc_ctrl_dev->reset_nb);
130 	return 0;
131 }
132 
133 static struct platform_driver litex_soc_ctrl_driver = {
134 	.driver = {
135 		.name = "litex-soc-controller",
136 		.of_match_table = of_match_ptr(litex_soc_ctrl_of_match)
137 	},
138 	.probe = litex_soc_ctrl_probe,
139 	.remove = litex_soc_ctrl_remove,
140 };
141 
142 module_platform_driver(litex_soc_ctrl_driver);
143 MODULE_DESCRIPTION("LiteX SoC Controller driver");
144 MODULE_AUTHOR("Antmicro <www.antmicro.com>");
145 MODULE_LICENSE("GPL v2");
146