arch/x86/kernel/i8237.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * 8237A DMA controller suspend functions.
   4  *
   5  * Written by Pierre Ossman, 2005.
   6  */
   7
   8 #include <linux/dmi.h>
   9 #include <linux/init.h>
  10 #include <linux/syscore_ops.h>
  11
  12 #include <asm/dma.h>
  13 #include <asm/x86_init.h>
  14
  15 /*
  16  * This module just handles suspend/resume issues with the
  17  * 8237A DMA controller (used for ISA and LPC).
  18  * Allocation is handled in kernel/dma.c and normal usage is
  19  * in asm/dma.h.
  20  */
  21
  22 static void i8237A_resume(void)
  23 {
  24         unsigned long flags;
  25         int i;
  26
  27         flags = claim_dma_lock();
  28
  29         dma_outb(0, DMA1_RESET_REG);
  30         dma_outb(0, DMA2_RESET_REG);
  31
  32         for (i = 0; i < 8; i++) {
  33                 set_dma_addr(i, 0x000000);
  34                 /* DMA count is a bit weird so this is not 0 */
  35                 set_dma_count(i, 1);
  36         }
  37
  38         /* Enable cascade DMA or channel 0-3 won't work */
  39         enable_dma(4);
  40
  41         release_dma_lock(flags);
  42 }
  43
  44 static struct syscore_ops i8237_syscore_ops = {
  45         .resume         = i8237A_resume,
  46 };
  47
  48 static int __init i8237A_init_ops(void)
  49 {
  50         /*
  51          * From SKL PCH onwards, the legacy DMA device is removed in which the
  52          * I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed
  53          * as well. All removed ports must return 0xff for a inb() request.
  54          *
  55          * Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting
  56          * the presence of DMA device since it may be used by BIOS to decode
  57          * LPC traffic for POST codes. Original LPC only decodes one byte of
  58          * port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x
  59          * decoding.
  60          */
  61         if (dma_inb(DMA_PAGE_0) == 0xFF)
  62                 return -ENODEV;
  63
  64         /*
  65          * It is not required to load this driver as newer SoC may not
  66          * support 8237 DMA or bus mastering from LPC. Platform firmware
  67          * must announce the support for such legacy devices via
  68          * ACPI_FADT_LEGACY_DEVICES field in FADT table.
  69          */
  70         if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017)
  71                 return -ENODEV;
  72
  73         register_syscore_ops(&i8237_syscore_ops);
  74         return 0;
  75 }
  76 device_initcall(i8237A_init_ops);