drivers/acpi/acpi_watchdog.c

   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  */
  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
  52 static bool acpi_watchdog_uses_rtc(const struct acpi_table_wdat *wdat)
  53 {
  54         return false;
  55 }
  56 #endif
  57
  58 static const struct acpi_table_wdat *acpi_watchdog_get_wdat(void)
  59 {
  60         const struct acpi_table_wdat *wdat = NULL;
  61         acpi_status status;
  62
  63         if (acpi_disabled)
  64                 return NULL;
  65
  66         status = acpi_get_table(ACPI_SIG_WDAT, 0,
  67                                 (struct acpi_table_header **)&wdat);
  68         if (ACPI_FAILURE(status)) {
  69                 /* It is fine if there is no WDAT */
  70                 return NULL;
  71         }
  72
  73         if (acpi_watchdog_uses_rtc(wdat)) {
  74                 pr_info("Skipping WDAT on this system because it uses RTC SRAM\n");
  75                 return NULL;
  76         }
  77
  78         return wdat;
  79 }
  80
  81 /**
  82  * Returns true if this system should prefer ACPI based watchdog instead of
  83  * the native one (which are typically the same hardware).
  84  */
  85 bool acpi_has_watchdog(void)
  86 {
  87         return !!acpi_watchdog_get_wdat();
  88 }
  89 EXPORT_SYMBOL_GPL(acpi_has_watchdog);
  90
  91 void __init acpi_watchdog_init(void)
  92 {
  93         const struct acpi_wdat_entry *entries;
  94         const struct acpi_table_wdat *wdat;
  95         struct list_head resource_list;
  96         struct resource_entry *rentry;
  97         struct platform_device *pdev;
  98         struct resource *resources;
  99         size_t nresources = 0;
 100         int i;
 101
 102         wdat = acpi_watchdog_get_wdat();
 103         if (!wdat) {
 104                 /* It is fine if there is no WDAT */
 105                 return;
 106         }
 107
 108         /* Watchdog disabled by BIOS */
 109         if (!(wdat->flags & ACPI_WDAT_ENABLED))
 110                 return;
 111
 112         /* Skip legacy PCI WDT devices */
 113         if (wdat->pci_segment != 0xff || wdat->pci_bus != 0xff ||
 114             wdat->pci_device != 0xff || wdat->pci_function != 0xff)
 115                 return;
 116
 117         INIT_LIST_HEAD(&resource_list);
 118
 119         entries = (struct acpi_wdat_entry *)(wdat + 1);
 120         for (i = 0; i < wdat->entries; i++) {
 121                 const struct acpi_generic_address *gas;
 122                 struct resource_entry *rentry;
 123                 struct resource res = {};
 124                 bool found;
 125
 126                 gas = &entries[i].register_region;
 127
 128                 res.start = gas->address;
 129                 if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
 130                         res.flags = IORESOURCE_MEM;
 131                         res.end = res.start + ALIGN(gas->access_width, 4) - 1;
 132                 } else if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
 133                         res.flags = IORESOURCE_IO;
 134                         res.end = res.start + gas->access_width - 1;
 135                 } else {
 136                         pr_warn("Unsupported address space: %u\n",
 137                                 gas->space_id);
 138                         goto fail_free_resource_list;
 139                 }
 140
 141                 found = false;
 142                 resource_list_for_each_entry(rentry, &resource_list) {
 143                         if (rentry->res->flags == res.flags &&
 144                             resource_overlaps(rentry->res, &res)) {
 145                                 if (res.start < rentry->res->start)
 146                                         rentry->res->start = res.start;
 147                                 if (res.end > rentry->res->end)
 148                                         rentry->res->end = res.end;
 149                                 found = true;
 150                                 break;
 151                         }
 152                 }
 153
 154                 if (!found) {
 155                         rentry = resource_list_create_entry(NULL, 0);
 156                         if (!rentry)
 157                                 goto fail_free_resource_list;
 158
 159                         *rentry->res = res;
 160                         resource_list_add_tail(rentry, &resource_list);
 161                         nresources++;
 162                 }
 163         }
 164
 165         resources = kcalloc(nresources, sizeof(*resources), GFP_KERNEL);
 166         if (!resources)
 167                 goto fail_free_resource_list;
 168
 169         i = 0;
 170         resource_list_for_each_entry(rentry, &resource_list)
 171                 resources[i++] = *rentry->res;
 172
 173         pdev = platform_device_register_simple("wdat_wdt", PLATFORM_DEVID_NONE,
 174                                                resources, nresources);
 175         if (IS_ERR(pdev))
 176                 pr_err("Device creation failed: %ld\n", PTR_ERR(pdev));
 177
 178         kfree(resources);
 179
 180 fail_free_resource_list:
 181         resource_list_free(&resource_list);
 182 }