1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright (C) 2018 Arm Ltd
4  * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
5  *
6  */
7 #include <common.h>
8 #include <dm.h>
9 #include <dm/read.h>
10 #include <asm/io.h>
11 #include <linux/delay.h>
12 #include <misc.h>
13 
14 #define SYS_CFGDATA		0xa0
15 
16 #define SYS_CFGCTRL		0xa4
17 #define SYS_CFGCTRL_START	BIT(31)
18 #define SYS_CFGCTRL_WRITE	BIT(30)
19 
20 #define SYS_CFGSTAT		0xa8
21 #define SYS_CFGSTAT_ERR		BIT(1)
22 #define SYS_CFGSTAT_COMPLETE	BIT(0)
23 
24 struct vexpress_config_sysreg {
25 	phys_addr_t addr;
26 	u32 site;
27 };
28 
29 static int vexpress_config_exec(struct vexpress_config_sysreg *syscfg,
30 				bool write, void *buf, int size)
31 {
32 	u32 cmd, status, tries = 100;
33 
34 	cmd = (*(u32 *)buf) | SYS_CFGCTRL_START | (syscfg->site << 16);
35 
36 	if (!write) {
37 		/* write a canary in the data register for reads */
38 		writel(0xdeadbeef, syscfg->addr + SYS_CFGDATA);
39 	} else {
40 		cmd |= SYS_CFGCTRL_WRITE;
41 		writel(((u32 *)buf)[1], syscfg->addr + SYS_CFGDATA);
42 	}
43 	writel(0, syscfg->addr + SYS_CFGSTAT);
44 	writel(cmd, syscfg->addr + SYS_CFGCTRL);
45 
46 	/* completion of command takes ages, go to sleep (150us) */
47 	do {
48 		udelay(150);
49 		status = readl(syscfg->addr + SYS_CFGSTAT);
50 		if (status & SYS_CFGSTAT_ERR)
51 			return -EFAULT;
52 	} while (--tries && !(status & SYS_CFGSTAT_COMPLETE));
53 
54 	if (!tries)
55 		return -ETIMEDOUT;
56 
57 	if (!write)
58 		(*(u32 *)buf) = readl(syscfg->addr + SYS_CFGDATA);
59 
60 	return 0;
61 }
62 
63 static int vexpress_config_read(struct udevice *dev,
64 				int offset, void *buf, int size)
65 {
66 	struct vexpress_config_sysreg *priv = dev_get_uclass_priv(dev);
67 
68 	if (size != sizeof(u32))
69 		return -EINVAL;
70 
71 	return vexpress_config_exec(priv, false, buf, size);
72 }
73 
74 static int vexpress_config_write(struct udevice *dev,
75 				 int offset, const void *buf, int size)
76 {
77 	struct vexpress_config_sysreg *priv = dev_get_uclass_priv(dev);
78 
79 	if (size != sizeof(u32) * 2)
80 		return -EINVAL;
81 
82 	return vexpress_config_exec(priv, true, (void *)buf, size);
83 }
84 
85 static struct misc_ops vexpress_config_ops = {
86 	.read = vexpress_config_read,
87 	.write = vexpress_config_write,
88 };
89 
90 static int vexpress_config_probe(struct udevice *dev)
91 {
92 	struct ofnode_phandle_args args;
93 	struct vexpress_config_sysreg *priv;
94 	const char *prop;
95 	int err, prop_size;
96 
97 	err = dev_read_phandle_with_args(dev, "arm,vexpress,config-bridge",
98 					 NULL, 0, 0, &args);
99 	if (err)
100 		return err;
101 
102 	prop = ofnode_get_property(args.node, "compatible", &prop_size);
103 	if (!prop || (strncmp(prop, "arm,vexpress-sysreg", 19) != 0))
104 		return -ENOENT;
105 
106 	priv = calloc(1, sizeof(*priv));
107 	if (!priv)
108 		return -ENOMEM;
109 
110 	dev->uclass_priv = priv;
111 	priv->addr = ofnode_get_addr(args.node);
112 
113 	return dev_read_u32(dev, "arm,vexpress,site", &priv->site);
114 }
115 
116 static const struct udevice_id vexpress_config_ids[] = {
117 	{ .compatible = "arm,vexpress,config-bus" },
118 	{ }
119 };
120 
121 U_BOOT_DRIVER(vexpress_config_drv) = {
122 	.name = "vexpress_config_bus",
123 	.id = UCLASS_MISC,
124 	.of_match = vexpress_config_ids,
125 	.bind = dm_scan_fdt_dev,
126 	.probe = vexpress_config_probe,
127 	.ops = &vexpress_config_ops,
128 };
129