1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IBM Real-Time Linux driver
4 *
5 * Copyright (C) IBM Corporation, 2010
6 *
7 * Author: Keith Mannthey <kmannth@us.ibm.com>
8 *         Vernon Mauery <vernux@us.ibm.com>
9 */
10
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/kernel.h>
14#include <linux/delay.h>
15#include <linux/module.h>
16#include <linux/io.h>
17#include <linux/dmi.h>
18#include <linux/efi.h>
19#include <linux/mutex.h>
20#include <asm/bios_ebda.h>
21
22#include <linux/io-64-nonatomic-lo-hi.h>
23
24static bool force;
25module_param(force, bool, 0);
26MODULE_PARM_DESC(force, "Force driver load, ignore DMI data");
27
28static bool debug;
29module_param(debug, bool, 0644);
30MODULE_PARM_DESC(debug, "Show debug output");
31
32MODULE_LICENSE("GPL");
33MODULE_AUTHOR("Keith Mannthey <kmmanth@us.ibm.com>");
34MODULE_AUTHOR("Vernon Mauery <vernux@us.ibm.com>");
35
36#define RTL_ADDR_TYPE_IO    1
37#define RTL_ADDR_TYPE_MMIO  2
38
39#define RTL_CMD_ENTER_PRTM  1
40#define RTL_CMD_EXIT_PRTM   2
41
42/* The RTL table as presented by the EBDA: */
43struct ibm_rtl_table {
44	char signature[5]; /* signature should be "_RTL_" */
45	u8 version;
46	u8 rt_status;
47	u8 command;
48	u8 command_status;
49	u8 cmd_address_type;
50	u8 cmd_granularity;
51	u8 cmd_offset;
52	u16 reserve1;
53	u32 cmd_port_address; /* platform dependent address */
54	u32 cmd_port_value;   /* platform dependent value */
55} __attribute__((packed));
56
57/* to locate "_RTL_" signature do a masked 5-byte integer compare */
58#define RTL_SIGNATURE 0x0000005f4c54525fULL
59#define RTL_MASK      0x000000ffffffffffULL
60
61#define RTL_DEBUG(fmt, ...)				\
62do {							\
63	if (debug)					\
64		pr_info(fmt, ##__VA_ARGS__);		\
65} while (0)
66
67static DEFINE_MUTEX(rtl_lock);
68static struct ibm_rtl_table __iomem *rtl_table;
69static void __iomem *ebda_map;
70static void __iomem *rtl_cmd_addr;
71static u8 rtl_cmd_type;
72static u8 rtl_cmd_width;
73
74static void __iomem *rtl_port_map(phys_addr_t addr, unsigned long len)
75{
76	if (rtl_cmd_type == RTL_ADDR_TYPE_MMIO)
77		return ioremap(addr, len);
78	return ioport_map(addr, len);
79}
80
81static void rtl_port_unmap(void __iomem *addr)
82{
83	if (addr && rtl_cmd_type == RTL_ADDR_TYPE_MMIO)
84		iounmap(addr);
85	else
86		ioport_unmap(addr);
87}
88
89static int ibm_rtl_write(u8 value)
90{
91	int ret = 0, count = 0;
92	u32 cmd_port_val;
93
94	RTL_DEBUG("%s(%d)\n", __func__, value);
95
96	value = value == 1 ? RTL_CMD_ENTER_PRTM : RTL_CMD_EXIT_PRTM;
97
98	mutex_lock(&rtl_lock);
99
100	if (ioread8(&rtl_table->rt_status) != value) {
101		iowrite8(value, &rtl_table->command);
102
103		switch (rtl_cmd_width) {
104		case 8:
105			cmd_port_val = ioread8(&rtl_table->cmd_port_value);
106			RTL_DEBUG("cmd_port_val = %u\n", cmd_port_val);
107			iowrite8((u8)cmd_port_val, rtl_cmd_addr);
108			break;
109		case 16:
110			cmd_port_val = ioread16(&rtl_table->cmd_port_value);
111			RTL_DEBUG("cmd_port_val = %u\n", cmd_port_val);
112			iowrite16((u16)cmd_port_val, rtl_cmd_addr);
113			break;
114		case 32:
115			cmd_port_val = ioread32(&rtl_table->cmd_port_value);
116			RTL_DEBUG("cmd_port_val = %u\n", cmd_port_val);
117			iowrite32(cmd_port_val, rtl_cmd_addr);
118			break;
119		}
120
121		while (ioread8(&rtl_table->command)) {
122			msleep(10);
123			if (count++ > 500) {
124				pr_err("Hardware not responding to "
125				       "mode switch request\n");
126				ret = -EIO;
127				break;
128			}
129
130		}
131
132		if (ioread8(&rtl_table->command_status)) {
133			RTL_DEBUG("command_status reports failed command\n");
134			ret = -EIO;
135		}
136	}
137
138	mutex_unlock(&rtl_lock);
139	return ret;
140}
141
142static ssize_t rtl_show_version(struct device *dev,
143                                struct device_attribute *attr,
144                                char *buf)
145{
146	return sprintf(buf, "%d\n", (int)ioread8(&rtl_table->version));
147}
148
149static ssize_t rtl_show_state(struct device *dev,
150                              struct device_attribute *attr,
151                              char *buf)
152{
153	return sprintf(buf, "%d\n", ioread8(&rtl_table->rt_status));
154}
155
156static ssize_t rtl_set_state(struct device *dev,
157                             struct device_attribute *attr,
158                             const char *buf,
159                             size_t count)
160{
161	ssize_t ret;
162
163	if (count < 1 || count > 2)
164		return -EINVAL;
165
166	switch (buf[0]) {
167	case '0':
168		ret = ibm_rtl_write(0);
169		break;
170	case '1':
171		ret = ibm_rtl_write(1);
172		break;
173	default:
174		ret = -EINVAL;
175	}
176	if (ret >= 0)
177		ret = count;
178
179	return ret;
180}
181
182static const struct bus_type rtl_subsys = {
183	.name = "ibm_rtl",
184	.dev_name = "ibm_rtl",
185};
186
187static DEVICE_ATTR(version, S_IRUGO, rtl_show_version, NULL);
188static DEVICE_ATTR(state, 0600, rtl_show_state, rtl_set_state);
189
190static struct device_attribute *rtl_attributes[] = {
191	&dev_attr_version,
192	&dev_attr_state,
193	NULL
194};
195
196
197static int rtl_setup_sysfs(void) {
198	int ret, i;
199
200	ret = subsys_system_register(&rtl_subsys, NULL);
201	if (!ret) {
202		struct device *dev_root = bus_get_dev_root(&rtl_subsys);
203
204		if (dev_root) {
205			for (i = 0; rtl_attributes[i]; i ++)
206				device_create_file(dev_root, rtl_attributes[i]);
207			put_device(dev_root);
208		}
209	}
210	return ret;
211}
212
213static void rtl_teardown_sysfs(void) {
214	struct device *dev_root = bus_get_dev_root(&rtl_subsys);
215	int i;
216
217	if (dev_root) {
218		for (i = 0; rtl_attributes[i]; i ++)
219			device_remove_file(dev_root, rtl_attributes[i]);
220		put_device(dev_root);
221	}
222	bus_unregister(&rtl_subsys);
223}
224
225
226static const struct dmi_system_id ibm_rtl_dmi_table[] __initconst = {
227	{                                                  \
228		.matches = {                               \
229			DMI_MATCH(DMI_SYS_VENDOR, "IBM"),  \
230		},                                         \
231	},
232	{ }
233};
234
235static int __init ibm_rtl_init(void) {
236	unsigned long ebda_addr, ebda_size;
237	unsigned int ebda_kb;
238	int ret = -ENODEV, i;
239
240	if (force)
241		pr_warn("module loaded by force\n");
242	/* first ensure that we are running on IBM HW */
243	else if (efi_enabled(EFI_BOOT) || !dmi_check_system(ibm_rtl_dmi_table))
244		return -ENODEV;
245
246	/* Get the address for the Extended BIOS Data Area */
247	ebda_addr = get_bios_ebda();
248	if (!ebda_addr) {
249		RTL_DEBUG("no BIOS EBDA found\n");
250		return -ENODEV;
251	}
252
253	ebda_map = ioremap(ebda_addr, 4);
254	if (!ebda_map)
255		return -ENOMEM;
256
257	/* First word in the EDBA is the Size in KB */
258	ebda_kb = ioread16(ebda_map);
259	RTL_DEBUG("EBDA is %d kB\n", ebda_kb);
260
261	if (ebda_kb == 0)
262		goto out;
263
264	iounmap(ebda_map);
265	ebda_size = ebda_kb*1024;
266
267	/* Remap the whole table */
268	ebda_map = ioremap(ebda_addr, ebda_size);
269	if (!ebda_map)
270		return -ENOMEM;
271
272	/* search for the _RTL_ signature at the start of the table */
273	for (i = 0 ; i < ebda_size/sizeof(unsigned int); i++) {
274		struct ibm_rtl_table __iomem * tmp;
275		tmp = (struct ibm_rtl_table __iomem *) (ebda_map+i);
276		if ((readq(&tmp->signature) & RTL_MASK) == RTL_SIGNATURE) {
277			phys_addr_t addr;
278			unsigned int plen;
279			RTL_DEBUG("found RTL_SIGNATURE at %p\n", tmp);
280			rtl_table = tmp;
281			/* The address, value, width and offset are platform
282			 * dependent and found in the ibm_rtl_table */
283			rtl_cmd_width = ioread8(&rtl_table->cmd_granularity);
284			rtl_cmd_type = ioread8(&rtl_table->cmd_address_type);
285			RTL_DEBUG("rtl_cmd_width = %u, rtl_cmd_type = %u\n",
286				  rtl_cmd_width, rtl_cmd_type);
287			addr = ioread32(&rtl_table->cmd_port_address);
288			RTL_DEBUG("addr = %#llx\n", (unsigned long long)addr);
289			plen = rtl_cmd_width/sizeof(char);
290			rtl_cmd_addr = rtl_port_map(addr, plen);
291			RTL_DEBUG("rtl_cmd_addr = %p\n", rtl_cmd_addr);
292			if (!rtl_cmd_addr) {
293				ret = -ENOMEM;
294				break;
295			}
296			ret = rtl_setup_sysfs();
297			break;
298		}
299	}
300
301out:
302	if (ret) {
303		iounmap(ebda_map);
304		rtl_port_unmap(rtl_cmd_addr);
305	}
306
307	return ret;
308}
309
310static void __exit ibm_rtl_exit(void)
311{
312	if (rtl_table) {
313		RTL_DEBUG("cleaning up");
314		/* do not leave the machine in SMI-free mode */
315		ibm_rtl_write(0);
316		/* unmap, unlink and remove all traces */
317		rtl_teardown_sysfs();
318		iounmap(ebda_map);
319		rtl_port_unmap(rtl_cmd_addr);
320	}
321}
322
323module_init(ibm_rtl_init);
324module_exit(ibm_rtl_exit);
325