// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for the CS5535/CS5536 Multi-Function General Purpose Timers (MFGPT)
 *
 * Copyright (C) 2006, Advanced Micro Devices, Inc.
 * Copyright (C) 2007  Andres Salomon <dilinger@debian.org>
 * Copyright (C) 2009  Andres Salomon <dilinger@collabora.co.uk>
 *
 * The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book.
 */

#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/cs5535.h>
#include <linux/slab.h>
#include <asm/msr.h>

#define DRV_NAME "cs5535-mfgpt"

static int mfgpt_reset_timers;
module_param_named(mfgptfix, mfgpt_reset_timers, int, 0644);
MODULE_PARM_DESC(mfgptfix, "Try to reset the MFGPT timers during init; "
                "required by some broken BIOSes (ie, TinyBIOS < 0.99) or kexec "
                "(1 = reset the MFGPT using an undocumented bit, "
                "2 = perform a soft reset by unconfiguring all timers); "
                "use what works best for you.");

struct cs5535_mfgpt_timer {
        struct cs5535_mfgpt_chip *chip;
        int nr;
};

static struct cs5535_mfgpt_chip {
        DECLARE_BITMAP(avail, MFGPT_MAX_TIMERS);
        resource_size_t base;

        struct platform_device *pdev;
        spinlock_t lock;
        int initialized;
} cs5535_mfgpt_chip;

int cs5535_mfgpt_toggle_event(struct cs5535_mfgpt_timer *timer, int cmp,
                int event, int enable)
{
        uint32_t msr, mask, value, dummy;
        int shift = (cmp == MFGPT_CMP1) ? 0 : 8;

        if (!timer) {
                WARN_ON(1);
                return -EIO;
        }

        /*
         * The register maps for these are described in sections 6.17.1.x of
         * the AMD Geode CS5536 Companion Device Data Book.
         */
        switch (event) {
        case MFGPT_EVENT_RESET:
                /*
                 * XXX: According to the docs, we cannot reset timers above
                 * 6; that is, resets for 7 and 8 will be ignored.  Is this
                 * a problem?   -dilinger
                 */
                msr = MSR_MFGPT_NR;
                mask = 1 << (timer->nr + 24);
                break;

        case MFGPT_EVENT_NMI:
                msr = MSR_MFGPT_NR;
                mask = 1 << (timer->nr + shift);
                break;

        case MFGPT_EVENT_IRQ:
                msr = MSR_MFGPT_IRQ;
                mask = 1 << (timer->nr + shift);
                break;

        default:
                return -EIO;
        }

        rdmsr(msr, value, dummy);

        if (enable)
                value |= mask;
        else
                value &= ~mask;

        wrmsr(msr, value, dummy);
        return 0;
}
EXPORT_SYMBOL_GPL(cs5535_mfgpt_toggle_event);

int cs5535_mfgpt_set_irq(struct cs5535_mfgpt_timer *timer, int cmp, int *irq,
                int enable)
{
        uint32_t zsel, lpc, dummy;
        int shift;

        if (!timer) {
                WARN_ON(1);
                return -EIO;
        }

        /*
         * Unfortunately, MFGPTs come in pairs sharing their IRQ lines. If VSA
         * is using the same CMP of the timer's Siamese twin, the IRQ is set to
         * 2, and we mustn't use nor change it.
         * XXX: Likewise, 2 Linux drivers might clash if the 2nd overwrites the
         * IRQ of the 1st. This can only happen if forcing an IRQ, calling this
         * with *irq==0 is safe. Currently there _are_ no 2 drivers.
         */
        rdmsr(MSR_PIC_ZSEL_LOW, zsel, dummy);
        shift = ((cmp == MFGPT_CMP1 ? 0 : 4) + timer->nr % 4) * 4;
        if (((zsel >> shift) & 0xF) == 2)
                return -EIO;

        /* Choose IRQ: if none supplied, keep IRQ already set or use default */
        if (!*irq)
                *irq = (zsel >> shift) & 0xF;
        if (!*irq)
                *irq = CONFIG_CS5535_MFGPT_DEFAULT_IRQ;

        /* Can't use IRQ if it's 0 (=disabled), 2, or routed to LPC */
        if (*irq < 1 || *irq == 2 || *irq > 15)
                return -EIO;
        rdmsr(MSR_PIC_IRQM_LPC, lpc, dummy);
        if (lpc & (1 << *irq))
                return -EIO;

        /* All chosen and checked - go for it */
        if (cs5535_mfgpt_toggle_event(timer, cmp, MFGPT_EVENT_IRQ, enable))
                return -EIO;
        if (enable) {
                zsel = (zsel & ~(0xF << shift)) | (*irq << shift);
                wrmsr(MSR_PIC_ZSEL_LOW, zsel, dummy);
        }

        return 0;
}
EXPORT_SYMBOL_GPL(cs5535_mfgpt_set_irq);

struct cs5535_mfgpt_timer *cs5535_mfgpt_alloc_timer(int timer_nr, int domain)
{
        struct cs5535_mfgpt_chip *mfgpt = &cs5535_mfgpt_chip;
        struct cs5535_mfgpt_timer *timer = NULL;
        unsigned long flags;
        int max;

        if (!mfgpt->initialized)
                goto done;

        /* only allocate timers from the working domain if requested */
        if (domain == MFGPT_DOMAIN_WORKING)
                max = 6;
        else
                max = MFGPT_MAX_TIMERS;

        if (timer_nr >= max) {
                /* programmer error.  silly programmers! */
                WARN_ON(1);
                goto done;
        }

        spin_lock_irqsave(&mfgpt->lock, flags);
        if (timer_nr < 0) {
                unsigned long t;

                /* try to find any available timer */
                t = find_first_bit(mfgpt->avail, max);
                /* set timer_nr to -1 if no timers available */
                timer_nr = t < max ? (int) t : -1;
        } else {
                /* check if the requested timer's available */
                if (!test_bit(timer_nr, mfgpt->avail))
                        timer_nr = -1;
        }

        if (timer_nr >= 0)
                /* if timer_nr is not -1, it's an available timer */
                __clear_bit(timer_nr, mfgpt->avail);
        spin_unlock_irqrestore(&mfgpt->lock, flags);

        if (timer_nr < 0)
                goto done;

        timer = kmalloc_obj(*timer);
        if (!timer) {
                /* aw hell */
                spin_lock_irqsave(&mfgpt->lock, flags);
                __set_bit(timer_nr, mfgpt->avail);
                spin_unlock_irqrestore(&mfgpt->lock, flags);
                goto done;
        }
        timer->chip = mfgpt;
        timer->nr = timer_nr;
        dev_info(&mfgpt->pdev->dev, "registered timer %d\n", timer_nr);

done:
        return timer;
}
EXPORT_SYMBOL_GPL(cs5535_mfgpt_alloc_timer);

/*
 * XXX: This frees the timer memory, but never resets the actual hardware
 * timer.  The old geode_mfgpt code did this; it would be good to figure
 * out a way to actually release the hardware timer.  See comments below.
 */
void cs5535_mfgpt_free_timer(struct cs5535_mfgpt_timer *timer)
{
        unsigned long flags;
        uint16_t val;

        /* timer can be made available again only if never set up */
        val = cs5535_mfgpt_read(timer, MFGPT_REG_SETUP);
        if (!(val & MFGPT_SETUP_SETUP)) {
                spin_lock_irqsave(&timer->chip->lock, flags);
                __set_bit(timer->nr, timer->chip->avail);
                spin_unlock_irqrestore(&timer->chip->lock, flags);
        }

        kfree(timer);
}
EXPORT_SYMBOL_GPL(cs5535_mfgpt_free_timer);

uint16_t cs5535_mfgpt_read(struct cs5535_mfgpt_timer *timer, uint16_t reg)
{
        return inw(timer->chip->base + reg + (timer->nr * 8));
}
EXPORT_SYMBOL_GPL(cs5535_mfgpt_read);

void cs5535_mfgpt_write(struct cs5535_mfgpt_timer *timer, uint16_t reg,
                uint16_t value)
{
        outw(value, timer->chip->base + reg + (timer->nr * 8));
}
EXPORT_SYMBOL_GPL(cs5535_mfgpt_write);

/*
 * This is a sledgehammer that resets all MFGPT timers. This is required by
 * some broken BIOSes which leave the system in an unstable state
 * (TinyBIOS 0.98, for example; fixed in 0.99).  It's uncertain as to
 * whether or not this secret MSR can be used to release individual timers.
 * Jordan tells me that he and Mitch once played w/ it, but it's unclear
 * what the results of that were (and they experienced some instability).
 */
static void reset_all_timers(void)
{
        uint32_t val, dummy;

        /* The following undocumented bit resets the MFGPT timers */
        val = 0xFF; dummy = 0;
        wrmsr(MSR_MFGPT_SETUP, val, dummy);
}

/*
 * This is another sledgehammer to reset all MFGPT timers.
 * Instead of using the undocumented bit method it clears
 * IRQ, NMI and RESET settings.
 */
static void soft_reset(void)
{
        int i;
        struct cs5535_mfgpt_timer t;

        for (i = 0; i < MFGPT_MAX_TIMERS; i++) {
                t.nr = i;

                cs5535_mfgpt_toggle_event(&t, MFGPT_CMP1, MFGPT_EVENT_RESET, 0);
                cs5535_mfgpt_toggle_event(&t, MFGPT_CMP2, MFGPT_EVENT_RESET, 0);
                cs5535_mfgpt_toggle_event(&t, MFGPT_CMP1, MFGPT_EVENT_NMI, 0);
                cs5535_mfgpt_toggle_event(&t, MFGPT_CMP2, MFGPT_EVENT_NMI, 0);
                cs5535_mfgpt_toggle_event(&t, MFGPT_CMP1, MFGPT_EVENT_IRQ, 0);
                cs5535_mfgpt_toggle_event(&t, MFGPT_CMP2, MFGPT_EVENT_IRQ, 0);
        }
}

/*
 * Check whether any MFGPTs are available for the kernel to use.  In most
 * cases, firmware that uses AMD's VSA code will claim all timers during
 * bootup; we certainly don't want to take them if they're already in use.
 * In other cases (such as with VSAless OpenFirmware), the system firmware
 * leaves timers available for us to use.
 */
static int scan_timers(struct cs5535_mfgpt_chip *mfgpt)
{
        struct cs5535_mfgpt_timer timer = { .chip = mfgpt };
        unsigned long flags;
        int timers = 0;
        uint16_t val;
        int i;

        /* bios workaround */
        if (mfgpt_reset_timers == 1)
                reset_all_timers();
        else if (mfgpt_reset_timers == 2)
                soft_reset();

        /* just to be safe, protect this section w/ lock */
        spin_lock_irqsave(&mfgpt->lock, flags);
        for (i = 0; i < MFGPT_MAX_TIMERS; i++) {
                timer.nr = i;
                val = cs5535_mfgpt_read(&timer, MFGPT_REG_SETUP);
                if (!(val & MFGPT_SETUP_SETUP) || mfgpt_reset_timers == 2) {
                        __set_bit(i, mfgpt->avail);
                        timers++;
                }
        }
        spin_unlock_irqrestore(&mfgpt->lock, flags);

        return timers;
}

static int cs5535_mfgpt_probe(struct platform_device *pdev)
{
        struct resource *res;
        int err = -EIO, t;

        if (mfgpt_reset_timers < 0 || mfgpt_reset_timers > 2) {
                dev_err(&pdev->dev, "Bad mfgpt_reset_timers value: %i\n",
                        mfgpt_reset_timers);
                goto done;
        }

        /* There are two ways to get the MFGPT base address; one is by
         * fetching it from MSR_LBAR_MFGPT, the other is by reading the
         * PCI BAR info.  The latter method is easier (especially across
         * different architectures), so we'll stick with that for now.  If
         * it turns out to be unreliable in the face of crappy BIOSes, we
         * can always go back to using MSRs.. */

        res = platform_get_resource(pdev, IORESOURCE_IO, 0);
        if (!res) {
                dev_err(&pdev->dev, "can't fetch device resource info\n");
                goto done;
        }

        if (!request_region(res->start, resource_size(res), pdev->name)) {
                dev_err(&pdev->dev, "can't request region\n");
                goto done;
        }

        /* set up the driver-specific struct */
        cs5535_mfgpt_chip.base = res->start;
        cs5535_mfgpt_chip.pdev = pdev;
        spin_lock_init(&cs5535_mfgpt_chip.lock);

        dev_info(&pdev->dev, "reserved resource region %pR\n", res);

        /* detect the available timers */
        t = scan_timers(&cs5535_mfgpt_chip);
        dev_info(&pdev->dev, "%d MFGPT timers available\n", t);
        cs5535_mfgpt_chip.initialized = 1;
        return 0;

done:
        return err;
}

static struct platform_driver cs5535_mfgpt_driver = {
        .driver = {
                .name = DRV_NAME,
        },
        .probe = cs5535_mfgpt_probe,
};


static int __init cs5535_mfgpt_init(void)
{
        return platform_driver_register(&cs5535_mfgpt_driver);
}

module_init(cs5535_mfgpt_init);

MODULE_AUTHOR("Andres Salomon <dilinger@queued.net>");
MODULE_DESCRIPTION("CS5535/CS5536 MFGPT timer driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRV_NAME);