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1  // SPDX-License-Identifier: GPL-2.0-only
2  /*
3   * ACPI watchdog table parsing support.
4   *
5   * Copyright (C) 2016, Intel Corporation
6   * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
7   */
8  
9  #define pr_fmt(fmt) "ACPI: watchdog: " fmt
10  
11  #include <linux/acpi.h>
12  #include <linux/ioport.h>
13  #include <linux/platform_device.h>
14  
15  #include "internal.h"
16  
17  #ifdef CONFIG_RTC_MC146818_LIB
18  #include <linux/mc146818rtc.h>
19  
20  /*
21   * There are several systems where the WDAT table is accessing RTC SRAM to
22   * store persistent information. This does not work well with the Linux RTC
23   * driver so on those systems we skip WDAT driver and prefer iTCO_wdt
24   * instead.
25   *
26   * See also https://bugzilla.kernel.org/show_bug.cgi?id=199033.
27   */
acpi_watchdog_uses_rtc(const struct acpi_table_wdat * wdat)28  static bool acpi_watchdog_uses_rtc(const struct acpi_table_wdat *wdat)
29  {
30  	const struct acpi_wdat_entry *entries;
31  	int i;
32  
33  	entries = (struct acpi_wdat_entry *)(wdat + 1);
34  	for (i = 0; i < wdat->entries; i++) {
35  		const struct acpi_generic_address *gas;
36  
37  		gas = &entries[i].register_region;
38  		if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
39  			switch (gas->address) {
40  			case RTC_PORT(0):
41  			case RTC_PORT(1):
42  			case RTC_PORT(2):
43  			case RTC_PORT(3):
44  				return true;
45  			}
46  		}
47  	}
48  
49  	return false;
50  }
51  #else
acpi_watchdog_uses_rtc(const struct acpi_table_wdat * wdat)52  static bool acpi_watchdog_uses_rtc(const struct acpi_table_wdat *wdat)
53  {
54  	return false;
55  }
56  #endif
57  
58  static bool acpi_no_watchdog;
59  
acpi_watchdog_get_wdat(void)60  static const struct acpi_table_wdat *acpi_watchdog_get_wdat(void)
61  {
62  	const struct acpi_table_wdat *wdat = NULL;
63  	acpi_status status;
64  
65  	if (acpi_disabled || acpi_no_watchdog)
66  		return NULL;
67  
68  	status = acpi_get_table(ACPI_SIG_WDAT, 0,
69  				(struct acpi_table_header **)&wdat);
70  	if (ACPI_FAILURE(status)) {
71  		/* It is fine if there is no WDAT */
72  		return NULL;
73  	}
74  
75  	if (acpi_watchdog_uses_rtc(wdat)) {
76  		acpi_put_table((struct acpi_table_header *)wdat);
77  		pr_info("Skipping WDAT on this system because it uses RTC SRAM\n");
78  		return NULL;
79  	}
80  
81  	return wdat;
82  }
83  
84  /**
85   * Returns true if this system should prefer ACPI based watchdog instead of
86   * the native one (which are typically the same hardware).
87   */
acpi_has_watchdog(void)88  bool acpi_has_watchdog(void)
89  {
90  	return !!acpi_watchdog_get_wdat();
91  }
92  EXPORT_SYMBOL_GPL(acpi_has_watchdog);
93  
94  /* ACPI watchdog can be disabled on boot command line */
disable_acpi_watchdog(char * str)95  static int __init disable_acpi_watchdog(char *str)
96  {
97  	acpi_no_watchdog = true;
98  	return 1;
99  }
100  __setup("acpi_no_watchdog", disable_acpi_watchdog);
101  
acpi_watchdog_init(void)102  void __init acpi_watchdog_init(void)
103  {
104  	const struct acpi_wdat_entry *entries;
105  	const struct acpi_table_wdat *wdat;
106  	struct list_head resource_list;
107  	struct resource_entry *rentry;
108  	struct platform_device *pdev;
109  	struct resource *resources;
110  	size_t nresources = 0;
111  	int i;
112  
113  	wdat = acpi_watchdog_get_wdat();
114  	if (!wdat) {
115  		/* It is fine if there is no WDAT */
116  		return;
117  	}
118  
119  	/* Watchdog disabled by BIOS */
120  	if (!(wdat->flags & ACPI_WDAT_ENABLED))
121  		goto fail_put_wdat;
122  
123  	/* Skip legacy PCI WDT devices */
124  	if (wdat->pci_segment != 0xff || wdat->pci_bus != 0xff ||
125  	    wdat->pci_device != 0xff || wdat->pci_function != 0xff)
126  		goto fail_put_wdat;
127  
128  	INIT_LIST_HEAD(&resource_list);
129  
130  	entries = (struct acpi_wdat_entry *)(wdat + 1);
131  	for (i = 0; i < wdat->entries; i++) {
132  		const struct acpi_generic_address *gas;
133  		struct resource_entry *rentry;
134  		struct resource res = {};
135  		bool found;
136  
137  		gas = &entries[i].register_region;
138  
139  		res.start = gas->address;
140  		res.end = res.start + ACPI_ACCESS_BYTE_WIDTH(gas->access_width) - 1;
141  		if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
142  			res.flags = IORESOURCE_MEM;
143  		} else if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
144  			res.flags = IORESOURCE_IO;
145  		} else {
146  			pr_warn("Unsupported address space: %u\n",
147  				gas->space_id);
148  			goto fail_free_resource_list;
149  		}
150  
151  		found = false;
152  		resource_list_for_each_entry(rentry, &resource_list) {
153  			if (rentry->res->flags == res.flags &&
154  			    resource_union(rentry->res, &res, rentry->res)) {
155  				found = true;
156  				break;
157  			}
158  		}
159  
160  		if (!found) {
161  			rentry = resource_list_create_entry(NULL, 0);
162  			if (!rentry)
163  				goto fail_free_resource_list;
164  
165  			*rentry->res = res;
166  			resource_list_add_tail(rentry, &resource_list);
167  			nresources++;
168  		}
169  	}
170  
171  	resources = kcalloc(nresources, sizeof(*resources), GFP_KERNEL);
172  	if (!resources)
173  		goto fail_free_resource_list;
174  
175  	i = 0;
176  	resource_list_for_each_entry(rentry, &resource_list)
177  		resources[i++] = *rentry->res;
178  
179  	pdev = platform_device_register_simple("wdat_wdt", PLATFORM_DEVID_NONE,
180  					       resources, nresources);
181  	if (IS_ERR(pdev))
182  		pr_err("Device creation failed: %ld\n", PTR_ERR(pdev));
183  
184  	kfree(resources);
185  
186  fail_free_resource_list:
187  	resource_list_free(&resource_list);
188  fail_put_wdat:
189  	acpi_put_table((struct acpi_table_header *)wdat);
190  }
191