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/*
* 8237A DMA controller suspend functions.
*
* Written by Pierre Ossman, 2005.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*/
#include <linux/dmi.h>
#include <linux/init.h>
#include <linux/syscore_ops.h>
#include <asm/dma.h>
#include <asm/x86_init.h>
/*
* This module just handles suspend/resume issues with the
* 8237A DMA controller (used for ISA and LPC).
* Allocation is handled in kernel/dma.c and normal usage is
* in asm/dma.h.
*/
static void i8237A_resume(void)
{
unsigned long flags;
int i;
flags = claim_dma_lock();
dma_outb(0, DMA1_RESET_REG);
dma_outb(0, DMA2_RESET_REG);
for (i = 0; i < 8; i++) {
set_dma_addr(i, 0x000000);
/* DMA count is a bit weird so this is not 0 */
set_dma_count(i, 1);
}
/* Enable cascade DMA or channel 0-3 won't work */
enable_dma(4);
release_dma_lock(flags);
}
static struct syscore_ops i8237_syscore_ops = {
.resume = i8237A_resume,
};
static int __init i8237A_init_ops(void)
{
/*
* From SKL PCH onwards, the legacy DMA device is removed in which the
* I/O ports (81h-83h, 87h, 89h-8Bh, 8Fh) related to it are removed
* as well. All removed ports must return 0xff for a inb() request.
*
* Note: DMA_PAGE_2 (port 0x81) should not be checked for detecting
* the presence of DMA device since it may be used by BIOS to decode
* LPC traffic for POST codes. Original LPC only decodes one byte of
* port 0x80 but some BIOS may choose to enhance PCH LPC port 0x8x
* decoding.
*/
if (dma_inb(DMA_PAGE_0) == 0xFF)
return -ENODEV;
/*
* It is not required to load this driver as newer SoC may not
* support 8237 DMA or bus mastering from LPC. Platform firmware
* must announce the support for such legacy devices via
* ACPI_FADT_LEGACY_DEVICES field in FADT table.
*/
if (x86_pnpbios_disabled() && dmi_get_bios_year() >= 2017)
return -ENODEV;
register_syscore_ops(&i8237_syscore_ops);
return 0;
}
device_initcall(i8237A_init_ops);
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