// SPDX-License-Identifier: GPL-2.0+
/*
 *      intel TCO vendor specific watchdog driver support
 *
 *      (c) Copyright 2006-2009 Wim Van Sebroeck <wim@iguana.be>.
 *
 *      Neither Wim Van Sebroeck nor Iguana vzw. admit liability nor
 *      provide warranty for any of this software. This material is
 *      provided "AS-IS" and at no charge.
 */

/*
 *      Includes, defines, variables, module parameters, ...
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

/* Module and version information */
#define DRV_NAME        "iTCO_vendor_support"
#define DRV_VERSION     "1.04"

/* Includes */
#include <linux/module.h>               /* For module specific items */
#include <linux/moduleparam.h>          /* For new moduleparam's */
#include <linux/types.h>                /* For standard types (like size_t) */
#include <linux/errno.h>                /* For the -ENODEV/... values */
#include <linux/kernel.h>               /* For printk/panic/... */
#include <linux/init.h>                 /* For __init/__exit/... */
#include <linux/ioport.h>               /* For io-port access */
#include <linux/io.h>                   /* For inb/outb/... */

#include "iTCO_vendor.h"

/* List of vendor support modes */
/* SuperMicro Pentium 3 Era 370SSE+-OEM1/P3TSSE */
#define SUPERMICRO_OLD_BOARD    1
/* SuperMicro Pentium 4 / Xeon 4 / EMT64T Era Systems - no longer supported */
#define SUPERMICRO_NEW_BOARD    2
/* Broken BIOS */
#define BROKEN_BIOS             911

int iTCO_vendorsupport;
EXPORT_SYMBOL(iTCO_vendorsupport);

module_param_named(vendorsupport, iTCO_vendorsupport, int, 0);
MODULE_PARM_DESC(vendorsupport, "iTCO vendor specific support mode, default="
                        "0 (none), 1=SuperMicro Pent3, 911=Broken SMI BIOS");

/*
 *      Vendor Specific Support
 */

/*
 *      Vendor Support: 1
 *      Board: Super Micro Computer Inc. 370SSE+-OEM1/P3TSSE
 *      iTCO chipset: ICH2
 *
 *      Code contributed by: R. Seretny <lkpatches@paypc.com>
 *      Documentation obtained by R. Seretny from SuperMicro Technical Support
 *
 *      To enable Watchdog function:
 *          BIOS setup -> Power -> TCO Logic SMI Enable -> Within5Minutes
 *          This setting enables SMI to clear the watchdog expired flag.
 *          If BIOS or CPU fail which may cause SMI hang, then system will
 *          reboot. When application starts to use watchdog function,
 *          application has to take over the control from SMI.
 *
 *          For P3TSSE, J36 jumper needs to be removed to enable the Watchdog
 *          function.
 *
 *          Note: The system will reboot when Expire Flag is set TWICE.
 *          So, if the watchdog timer is 20 seconds, then the maximum hang
 *          time is about 40 seconds, and the minimum hang time is about
 *          20.6 seconds.
 */

static void supermicro_old_pre_start(struct resource *smires)
{
        unsigned long val32;

        /* Bit 13: TCO_EN -> 0 = Disables TCO logic generating an SMI# */
        val32 = inl(smires->start);
        val32 &= 0xffffdfff;    /* Turn off SMI clearing watchdog */
        outl(val32, smires->start);     /* Needed to activate watchdog */
}

static void supermicro_old_pre_stop(struct resource *smires)
{
        unsigned long val32;

        /* Bit 13: TCO_EN -> 1 = Enables the TCO logic to generate SMI# */
        val32 = inl(smires->start);
        val32 |= 0x00002000;    /* Turn on SMI clearing watchdog */
        outl(val32, smires->start);     /* Needed to deactivate watchdog */
}

/*
 *      Vendor Support: 911
 *      Board: Some Intel ICHx based motherboards
 *      iTCO chipset: ICH7+
 *
 *      Some Intel motherboards have a broken BIOS implementation: i.e.
 *      the SMI handler clear's the TIMEOUT bit in the TC01_STS register
 *      and does not reload the time. Thus the TCO watchdog does not reboot
 *      the system.
 *
 *      These are the conclusions of Andriy Gapon <avg@icyb.net.ua> after
 *      debugging: the SMI handler is quite simple - it tests value in
 *      TCO1_CNT against 0x800, i.e. checks TCO_TMR_HLT. If the bit is set
 *      the handler goes into an infinite loop, apparently to allow the
 *      second timeout and reboot. Otherwise it simply clears TIMEOUT bit
 *      in TCO1_STS and that's it.
 *      So the logic seems to be reversed, because it is hard to see how
 *      TIMEOUT can get set to 1 and SMI generated when TCO_TMR_HLT is set
 *      (other than a transitional effect).
 *
 *      The only fix found to get the motherboard(s) to reboot is to put
 *      the glb_smi_en bit to 0. This is a dirty hack that bypasses the
 *      broken code by disabling Global SMI.
 *
 *      WARNING: globally disabling SMI could possibly lead to dramatic
 *      problems, especially on laptops! I.e. various ACPI things where
 *      SMI is used for communication between OS and firmware.
 *
 *      Don't use this fix if you don't need to!!!
 */

static void broken_bios_start(struct resource *smires)
{
        unsigned long val32;

        val32 = inl(smires->start);
        /* Bit 13: TCO_EN     -> 0 = Disables TCO logic generating an SMI#
           Bit  0: GBL_SMI_EN -> 0 = No SMI# will be generated by ICH. */
        val32 &= 0xffffdffe;
        outl(val32, smires->start);
}

static void broken_bios_stop(struct resource *smires)
{
        unsigned long val32;

        val32 = inl(smires->start);
        /* Bit 13: TCO_EN     -> 1 = Enables TCO logic generating an SMI#
           Bit  0: GBL_SMI_EN -> 1 = Turn global SMI on again. */
        val32 |= 0x00002001;
        outl(val32, smires->start);
}

/*
 *      Generic Support Functions
 */

void iTCO_vendor_pre_start(struct resource *smires,
                           unsigned int heartbeat)
{
        switch (iTCO_vendorsupport) {
        case SUPERMICRO_OLD_BOARD:
                supermicro_old_pre_start(smires);
                break;
        case BROKEN_BIOS:
                broken_bios_start(smires);
                break;
        }
}
EXPORT_SYMBOL(iTCO_vendor_pre_start);

void iTCO_vendor_pre_stop(struct resource *smires)
{
        switch (iTCO_vendorsupport) {
        case SUPERMICRO_OLD_BOARD:
                supermicro_old_pre_stop(smires);
                break;
        case BROKEN_BIOS:
                broken_bios_stop(smires);
                break;
        }
}
EXPORT_SYMBOL(iTCO_vendor_pre_stop);

int iTCO_vendor_check_noreboot_on(void)
{
        switch (iTCO_vendorsupport) {
        case SUPERMICRO_OLD_BOARD:
                return 0;
        default:
                return 1;
        }
}
EXPORT_SYMBOL(iTCO_vendor_check_noreboot_on);

static int __init iTCO_vendor_init_module(void)
{
        if (iTCO_vendorsupport == SUPERMICRO_NEW_BOARD) {
                pr_warn("Option vendorsupport=%d is no longer supported, "
                        "please use the w83627hf_wdt driver instead\n",
                        SUPERMICRO_NEW_BOARD);
                return -EINVAL;
        }
        pr_info("vendor-support=%d\n", iTCO_vendorsupport);
        return 0;
}

static void __exit iTCO_vendor_exit_module(void)
{
        pr_info("Module Unloaded\n");
}

module_init(iTCO_vendor_init_module);
module_exit(iTCO_vendor_exit_module);

MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>, "
                "R. Seretny <lkpatches@paypc.com>");
MODULE_DESCRIPTION("Intel TCO Vendor Specific WatchDog Timer Driver Support");
MODULE_VERSION(DRV_VERSION);
MODULE_LICENSE("GPL");