drivers/acpi/acpi_watchdog.c

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