/*
 * Driver/API for AMD Geode Multi-Function General Purpose Timers (MFGPT)
 *
 * Copyright (C) 2006, Advanced Micro Devices, Inc.
 * Copyright (C) 2007, Andres Salomon <dilinger@debian.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public License
 * as published by the Free Software Foundation.
 *
 * The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book.
 */

/*
 * We are using the 32Khz input clock - its the only one that has the
 * ranges we find desirable.  The following table lists the suitable
 * divisors and the associated hz, minimum interval
 * and the maximum interval:
 *
 *  Divisor   Hz      Min Delta (S) Max Delta (S)
 *   1        32000     .0005          2.048
 *   2        16000      .001          4.096
 *   4         8000      .002          8.192
 *   8         4000      .004         16.384
 *   16        2000      .008         32.768
 *   32        1000      .016         65.536
 *   64         500      .032        131.072
 *  128         250      .064        262.144
 *  256         125      .128        524.288
 */

#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <asm/geode.h>

#define F_AVAIL    0x01

static struct mfgpt_timer_t {
	int flags;
	struct module *owner;
} mfgpt_timers[MFGPT_MAX_TIMERS];

/* Selected from the table above */

#define MFGPT_DIVISOR 16
#define MFGPT_SCALE  4     /* divisor = 2^(scale) */
#define MFGPT_HZ  (32000 / MFGPT_DIVISOR)
#define MFGPT_PERIODIC (MFGPT_HZ / HZ)

/* Allow for disabling of MFGPTs */
static int disable;
static int __init mfgpt_disable(char *s)
{
	disable = 1;
	return 1;
}
__setup("nomfgpt", mfgpt_disable);

/*
 * 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.
 */
int __init geode_mfgpt_detect(void)
{
	int count = 0, i;
	u16 val;

	if (disable) {
		printk(KERN_INFO "geode-mfgpt:  Skipping MFGPT setup\n");
		return 0;
	}

	for (i = 0; i < MFGPT_MAX_TIMERS; i++) {
		val = geode_mfgpt_read(i, MFGPT_REG_SETUP);
		if (!(val & MFGPT_SETUP_SETUP)) {
			mfgpt_timers[i].flags = F_AVAIL;
			count++;
		}
	}

	return count;
}

int geode_mfgpt_toggle_event(int timer, int cmp, int event, int enable)
{
	u32 msr, mask, value, dummy;
	int shift = (cmp == MFGPT_CMP1) ? 0 : 8;

	if (timer < 0 || timer >= MFGPT_MAX_TIMERS)
		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 = MFGPT_NR_MSR;
		mask = 1 << (timer + 24);
		break;

	case MFGPT_EVENT_NMI:
		msr = MFGPT_NR_MSR;
		mask = 1 << (timer + shift);
		break;

	case MFGPT_EVENT_IRQ:
		msr = MFGPT_IRQ_MSR;
		mask = 1 << (timer + shift);
		break;

	default:
		return -EIO;
	}

	rdmsr(msr, value, dummy);

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

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

int geode_mfgpt_set_irq(int timer, int cmp, int irq, int enable)
{
	u32 val, dummy;
	int offset;

	if (timer < 0 || timer >= MFGPT_MAX_TIMERS)
		return -EIO;

	if (geode_mfgpt_toggle_event(timer, cmp, MFGPT_EVENT_IRQ, enable))
		return -EIO;

	rdmsr(MSR_PIC_ZSEL_LOW, val, dummy);

	offset = (timer % 4) * 4;

	val &= ~((0xF << offset) | (0xF << (offset + 16)));

	if (enable) {
		val |= (irq & 0x0F) << (offset);
		val |= (irq & 0x0F) << (offset + 16);
	}

	wrmsr(MSR_PIC_ZSEL_LOW, val, dummy);
	return 0;
}

static int mfgpt_get(int timer, struct module *owner)
{
	mfgpt_timers[timer].flags &= ~F_AVAIL;
	mfgpt_timers[timer].owner = owner;
	printk(KERN_INFO "geode-mfgpt:  Registered timer %d\n", timer);
	return timer;
}

int geode_mfgpt_alloc_timer(int timer, int domain, struct module *owner)
{
	int i;

	if (!geode_get_dev_base(GEODE_DEV_MFGPT))
		return -ENODEV;
	if (timer >= MFGPT_MAX_TIMERS)
		return -EIO;

	if (timer < 0) {
		/* Try to find an available timer */
		for (i = 0; i < MFGPT_MAX_TIMERS; i++) {
			if (mfgpt_timers[i].flags & F_AVAIL)
				return mfgpt_get(i, owner);

			if (i == 5 && domain == MFGPT_DOMAIN_WORKING)
				break;
		}
	} else {
		/* If they requested a specific timer, try to honor that */
		if (mfgpt_timers[timer].flags & F_AVAIL)
			return mfgpt_get(timer, owner);
	}

	/* No timers available - too bad */
	return -1;
}