lib/acpi/acpi.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Utility functions for ACPI
   4  *
   5  * Copyright 2023 Google LLC
   6  */
   7
   8 #include <mapmem.h>
   9 #include <acpi/acpi_table.h>
  10 #include <asm/global_data.h>
  11
  12 DECLARE_GLOBAL_DATA_PTR;
  13
  14 struct acpi_table_header *acpi_find_table(const char *sig)
  15 {
  16         struct acpi_rsdp *rsdp;
  17         struct acpi_rsdt *rsdt;
  18         struct acpi_xsdt *xsdt;
  19         int len, i, count;
  20
  21         rsdp = map_sysmem(gd_acpi_start(), 0);
  22         if (!rsdp)
  23                 return NULL;
  24         if (rsdp->xsdt_address) {
  25                 xsdt = map_sysmem(rsdp->xsdt_address, 0);
  26                 len = xsdt->header.length - sizeof(xsdt->header);
  27                 count = len / sizeof(u64);
  28         } else {
  29                 if (!rsdp->rsdt_address)
  30                         return NULL;
  31                 rsdt = map_sysmem(rsdp->rsdt_address, 0);
  32                 len = rsdt->header.length - sizeof(rsdt->header);
  33                 count = len / sizeof(u32);
  34         }
  35         for (i = 0; i < count; i++) {
  36                 struct acpi_table_header *hdr;
  37
  38                 if (rsdp->xsdt_address)
  39                         hdr = map_sysmem(xsdt->entry[i], 0);
  40                 else
  41                         hdr = map_sysmem(rsdt->entry[i], 0);
  42                 if (!memcmp(hdr->signature, sig, ACPI_NAME_LEN))
  43                         return hdr;
  44                 if (!memcmp(hdr->signature, "FACP", ACPI_NAME_LEN)) {
  45                         struct acpi_fadt *fadt = (struct acpi_fadt *)hdr;
  46
  47                         if (!memcmp(sig, "DSDT", ACPI_NAME_LEN) && fadt->dsdt)
  48                                 return map_sysmem(fadt->dsdt, 0);
  49                         if (!memcmp(sig, "FACS", ACPI_NAME_LEN) &&
  50                             fadt->firmware_ctrl)
  51                                 return map_sysmem(fadt->firmware_ctrl, 0);
  52                 }
  53         }
  54
  55         return NULL;
  56 }