// 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);