drivers/acpi/acpi_cmos_rtc.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * ACPI support for CMOS RTC Address Space access
   4  *
   5  * Copyright (C) 2013, Intel Corporation
   6  * Authors: Lan Tianyu <tianyu.lan@intel.com>
   7  */
   8
   9 #include <linux/acpi.h>
  10 #include <linux/device.h>
  11 #include <linux/err.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/mc146818rtc.h>
  15
  16 #include "internal.h"
  17
  18 static const struct acpi_device_id acpi_cmos_rtc_ids[] = {
  19         { "PNP0B00" },
  20         { "PNP0B01" },
  21         { "PNP0B02" },
  22         {}
  23 };
  24
  25 static acpi_status
  26 acpi_cmos_rtc_space_handler(u32 function, acpi_physical_address address,
  27                       u32 bits, u64 *value64,
  28                       void *handler_context, void *region_context)
  29 {
  30         int i;
  31         u8 *value = (u8 *)value64;
  32
  33         if (address > 0xff || !value64)
  34                 return AE_BAD_PARAMETER;
  35
  36         if (function != ACPI_WRITE && function != ACPI_READ)
  37                 return AE_BAD_PARAMETER;
  38
  39         spin_lock_irq(&rtc_lock);
  40
  41         for (i = 0; i < DIV_ROUND_UP(bits, 8); ++i, ++address, ++value)
  42                 if (function == ACPI_READ)
  43                         *value = CMOS_READ(address);
  44                 else
  45                         CMOS_WRITE(*value, address);
  46
  47         spin_unlock_irq(&rtc_lock);
  48
  49         return AE_OK;
  50 }
  51
  52 static int acpi_install_cmos_rtc_space_handler(struct acpi_device *adev,
  53                 const struct acpi_device_id *id)
  54 {
  55         acpi_status status;
  56
  57         status = acpi_install_address_space_handler(adev->handle,
  58                         ACPI_ADR_SPACE_CMOS,
  59                         &acpi_cmos_rtc_space_handler,
  60                         NULL, NULL);
  61         if (ACPI_FAILURE(status)) {
  62                 pr_err(PREFIX "Error installing CMOS-RTC region handler\n");
  63                 return -ENODEV;
  64         }
  65
  66         return 1;
  67 }
  68
  69 static void acpi_remove_cmos_rtc_space_handler(struct acpi_device *adev)
  70 {
  71         if (ACPI_FAILURE(acpi_remove_address_space_handler(adev->handle,
  72                         ACPI_ADR_SPACE_CMOS, &acpi_cmos_rtc_space_handler)))
  73                 pr_err(PREFIX "Error removing CMOS-RTC region handler\n");
  74 }
  75
  76 static struct acpi_scan_handler cmos_rtc_handler = {
  77         .ids = acpi_cmos_rtc_ids,
  78         .attach = acpi_install_cmos_rtc_space_handler,
  79         .detach = acpi_remove_cmos_rtc_space_handler,
  80 };
  81
  82 void __init acpi_cmos_rtc_init(void)
  83 {
  84         acpi_scan_add_handler(&cmos_rtc_handler);
  85 }