arch/x86/kernel/i8237.c

   1 /*
   2  * 8237A DMA controller suspend functions.
   3  *
   4  * Written by Pierre Ossman, 2005.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or (at
   9  * your option) any later version.
  10  */
  11
  12 #include <linux/dmi.h>
  13 #include <linux/init.h>
  14 #include <linux/syscore_ops.h>
  15
  16 #include <asm/dma.h>
  17 #include <asm/x86_init.h>
  18
  19 /*
  20  * This module just handles suspend/resume issues with the
  21  * 8237A DMA controller (used for ISA and LPC).
  22  * Allocation is handled in kernel/dma.c and normal usage is
  23  * in asm/dma.h.
  24  */
  25
  26 static void i8237A_resume(void)
  27 {
  28         unsigned long flags;
  29         int i;
  30
  31         flags = claim_dma_lock();
  32
  33         dma_outb(0, DMA1_RESET_REG);
  34         dma_outb(0, DMA2_RESET_REG);
  35
  36         for (i = 0; i < 8; i++) {
  37                 set_dma_addr(i, 0x000000);
  38                 /* DMA count is a bit weird so this is not 0 */
  39                 set_dma_count(i, 1);
  40         }
  41
  42         /* Enable cascade DMA or channel 0-3 won't work */
  43         enable_dma(4);
  44
  45         release_dma_lock(flags);
  46 }
  47
  48 static struct syscore_ops i8237_syscore_ops = {
  49         .resume         = i8237A_resume,
  50 };
  51
  52 static int __init i8237A_init_ops(void)
  53 {
  54         /*
  55          * From SKL PCH onwards, the legacy DMA device is removed in which the
  56          * I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed
  57          * as well. All removed ports must return 0xff for a inb() request.
  58          *
  59          * Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting
  60          * the presence of DMA device since it may be used by BIOS to decode
  61          * LPC traffic for POST codes. Original LPC only decodes one byte of
  62          * port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x
  63          * decoding.
  64          */
  65         if (dma_inb(DMA_PAGE_0) == 0xFF)
  66                 return -ENODEV;
  67
  68         /*
  69          * It is not required to load this driver as newer SoC may not
  70          * support 8237 DMA or bus mastering from LPC. Platform firmware
  71          * must announce the support for such legacy devices via
  72          * ACPI_FADT_LEGACY_DEVICES field in FADT table.
  73          */
  74         if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017)
  75                 return -ENODEV;
  76
  77         register_syscore_ops(&i8237_syscore_ops);
  78         return 0;
  79 }
  80 device_initcall(i8237A_init_ops);