1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2018 Arm Ltd
4 * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
11 #include <linux/delay.h>
14 #define SYS_CFGDATA 0xa0
16 #define SYS_CFGCTRL 0xa4
17 #define SYS_CFGCTRL_START BIT(31)
18 #define SYS_CFGCTRL_WRITE BIT(30)
20 #define SYS_CFGSTAT 0xa8
21 #define SYS_CFGSTAT_ERR BIT(1)
22 #define SYS_CFGSTAT_COMPLETE BIT(0)
24 struct vexpress_config_sysreg {
29 static int vexpress_config_exec(struct vexpress_config_sysreg *syscfg,
30 bool write, void *buf, int size)
32 u32 cmd, status, tries = 100;
34 cmd = (*(u32 *)buf) | SYS_CFGCTRL_START | (syscfg->site << 16);
37 /* write a canary in the data register for reads */
38 writel(0xdeadbeef, syscfg->addr + SYS_CFGDATA);
40 cmd |= SYS_CFGCTRL_WRITE;
41 writel(((u32 *)buf)[1], syscfg->addr + SYS_CFGDATA);
43 writel(0, syscfg->addr + SYS_CFGSTAT);
44 writel(cmd, syscfg->addr + SYS_CFGCTRL);
46 /* completion of command takes ages, go to sleep (150us) */
49 status = readl(syscfg->addr + SYS_CFGSTAT);
50 if (status & SYS_CFGSTAT_ERR)
52 } while (--tries && !(status & SYS_CFGSTAT_COMPLETE));
58 (*(u32 *)buf) = readl(syscfg->addr + SYS_CFGDATA);
63 static int vexpress_config_read(struct udevice *dev,
64 int offset, void *buf, int size)
66 struct vexpress_config_sysreg *priv = dev_get_uclass_priv(dev);
68 if (size != sizeof(u32))
71 return vexpress_config_exec(priv, false, buf, size);
74 static int vexpress_config_write(struct udevice *dev,
75 int offset, const void *buf, int size)
77 struct vexpress_config_sysreg *priv = dev_get_uclass_priv(dev);
79 if (size != sizeof(u32) * 2)
82 return vexpress_config_exec(priv, true, (void *)buf, size);
85 static struct misc_ops vexpress_config_ops = {
86 .read = vexpress_config_read,
87 .write = vexpress_config_write,
90 static int vexpress_config_probe(struct udevice *dev)
92 struct ofnode_phandle_args args;
93 struct vexpress_config_sysreg *priv;
97 err = dev_read_phandle_with_args(dev, "arm,vexpress,config-bridge",
102 prop = ofnode_get_property(args.node, "compatible", &prop_size);
103 if (!prop || (strncmp(prop, "arm,vexpress-sysreg", 19) != 0))
106 priv = calloc(1, sizeof(*priv));
110 dev->uclass_priv = priv;
111 priv->addr = ofnode_get_addr(args.node);
113 return dev_read_u32(dev, "arm,vexpress,site", &priv->site);
116 static const struct udevice_id vexpress_config_ids[] = {
117 { .compatible = "arm,vexpress,config-bus" },
121 U_BOOT_DRIVER(vexpress_config_drv) = {
122 .name = "vexpress_config_bus",
124 .of_match = vexpress_config_ids,
125 .bind = dm_scan_fdt_dev,
126 .probe = vexpress_config_probe,
127 .ops = &vexpress_config_ops,