// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 8237A DMA controller suspend functions.
 *
 * Written by Pierre Ossman, 2005.
 */

#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 *data)
{
        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 const struct syscore_ops i8237_syscore_ops = {
        .resume         = i8237A_resume,
};

static struct syscore i8237_syscore = {
        .ops = &i8237_syscore_ops,
};

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(&i8237_syscore);
        return 0;
}
device_initcall(i8237A_init_ops);