/*
 * Freescale General-purpose Timers Module
 *
 * Copyright (c) Freescale Semiconductor, Inc. 2006.
 *               Shlomi Gridish <gridish@freescale.com>
 *               Jerry Huang <Chang-Ming.Huang@freescale.com>
 * Copyright (c) MontaVista Software, Inc. 2008.
 *               Anton Vorontsov <avorontsov@ru.mvista.com>
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/spinlock.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <asm/fsl_gtm.h>

#define GTCFR_STP(x)            ((x) & 1 ? 1 << 5 : 1 << 1)
#define GTCFR_RST(x)            ((x) & 1 ? 1 << 4 : 1 << 0)

#define GTMDR_ICLK_MASK         (3 << 1)
#define GTMDR_ICLK_ICAS         (0 << 1)
#define GTMDR_ICLK_ICLK         (1 << 1)
#define GTMDR_ICLK_SLGO         (2 << 1)
#define GTMDR_FRR               (1 << 3)
#define GTMDR_ORI               (1 << 4)
#define GTMDR_SPS(x)            ((x) << 8)

struct gtm_timers_regs {
        u8      gtcfr1;         /* Timer 1, Timer 2 global config register */
        u8      res0[0x3];
        u8      gtcfr2;         /* Timer 3, timer 4 global config register */
        u8      res1[0xB];
        __be16  gtmdr1;         /* Timer 1 mode register */
        __be16  gtmdr2;         /* Timer 2 mode register */
        __be16  gtrfr1;         /* Timer 1 reference register */
        __be16  gtrfr2;         /* Timer 2 reference register */
        __be16  gtcpr1;         /* Timer 1 capture register */
        __be16  gtcpr2;         /* Timer 2 capture register */
        __be16  gtcnr1;         /* Timer 1 counter */
        __be16  gtcnr2;         /* Timer 2 counter */
        __be16  gtmdr3;         /* Timer 3 mode register */
        __be16  gtmdr4;         /* Timer 4 mode register */
        __be16  gtrfr3;         /* Timer 3 reference register */
        __be16  gtrfr4;         /* Timer 4 reference register */
        __be16  gtcpr3;         /* Timer 3 capture register */
        __be16  gtcpr4;         /* Timer 4 capture register */
        __be16  gtcnr3;         /* Timer 3 counter */
        __be16  gtcnr4;         /* Timer 4 counter */
        __be16  gtevr1;         /* Timer 1 event register */
        __be16  gtevr2;         /* Timer 2 event register */
        __be16  gtevr3;         /* Timer 3 event register */
        __be16  gtevr4;         /* Timer 4 event register */
        __be16  gtpsr1;         /* Timer 1 prescale register */
        __be16  gtpsr2;         /* Timer 2 prescale register */
        __be16  gtpsr3;         /* Timer 3 prescale register */
        __be16  gtpsr4;         /* Timer 4 prescale register */
        u8 res2[0x40];
} __attribute__ ((packed));

struct gtm {
        unsigned int clock;
        struct gtm_timers_regs __iomem *regs;
        struct gtm_timer timers[4];
        spinlock_t lock;
        struct list_head list_node;
};

static LIST_HEAD(gtms);

/**
 * gtm_get_timer - request GTM timer to use it with the rest of GTM API
 * Context:     non-IRQ
 *
 * This function reserves GTM timer for later use. It returns gtm_timer
 * structure to use with the rest of GTM API, you should use timer->irq
 * to manage timer interrupt.
 */
struct gtm_timer *gtm_get_timer16(void)
{
        struct gtm *gtm = NULL;
        int i;

        list_for_each_entry(gtm, &gtms, list_node) {
                spin_lock_irq(&gtm->lock);

                for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
                        if (!gtm->timers[i].requested) {
                                gtm->timers[i].requested = true;
                                spin_unlock_irq(&gtm->lock);
                                return &gtm->timers[i];
                        }
                }

                spin_unlock_irq(&gtm->lock);
        }

        if (gtm)
                return ERR_PTR(-EBUSY);
        return ERR_PTR(-ENODEV);
}
EXPORT_SYMBOL(gtm_get_timer16);

/**
 * gtm_get_specific_timer - request specific GTM timer
 * @gtm:        specific GTM, pass here GTM's device_node->data
 * @timer:      specific timer number, Timer1 is 0.
 * Context:     non-IRQ
 *
 * This function reserves GTM timer for later use. It returns gtm_timer
 * structure to use with the rest of GTM API, you should use timer->irq
 * to manage timer interrupt.
 */
struct gtm_timer *gtm_get_specific_timer16(struct gtm *gtm,
                                           unsigned int timer)
{
        struct gtm_timer *ret = ERR_PTR(-EBUSY);

        if (timer > 3)
                return ERR_PTR(-EINVAL);

        spin_lock_irq(&gtm->lock);

        if (gtm->timers[timer].requested)
                goto out;

        ret = &gtm->timers[timer];
        ret->requested = true;

out:
        spin_unlock_irq(&gtm->lock);
        return ret;
}
EXPORT_SYMBOL(gtm_get_specific_timer16);

/**
 * gtm_put_timer16 - release 16 bits GTM timer
 * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
 * Context:     any
 *
 * This function releases GTM timer so others may request it.
 */
void gtm_put_timer16(struct gtm_timer *tmr)
{
        gtm_stop_timer16(tmr);

        spin_lock_irq(&tmr->gtm->lock);
        tmr->requested = false;
        spin_unlock_irq(&tmr->gtm->lock);
}
EXPORT_SYMBOL(gtm_put_timer16);

/*
 * This is back-end for the exported functions, it's used to reset single
 * timer in reference mode.
 */
static int gtm_set_ref_timer16(struct gtm_timer *tmr, int frequency,
                               int reference_value, bool free_run)
{
        struct gtm *gtm = tmr->gtm;
        int num = tmr - &gtm->timers[0];
        unsigned int prescaler;
        u8 iclk = GTMDR_ICLK_ICLK;
        u8 psr;
        u8 sps;
        unsigned long flags;
        int max_prescaler = 256 * 256 * 16;

        /* CPM2 doesn't have primary prescaler */
        if (!tmr->gtpsr)
                max_prescaler /= 256;

        prescaler = gtm->clock / frequency;
        /*
         * We have two 8 bit prescalers -- primary and secondary (psr, sps),
         * plus "slow go" mode (clk / 16). So, total prescale value is
         * 16 * (psr + 1) * (sps + 1). Though, for CPM2 GTMs we losing psr.
         */
        if (prescaler > max_prescaler)
                return -EINVAL;

        if (prescaler > max_prescaler / 16) {
                iclk = GTMDR_ICLK_SLGO;
                prescaler /= 16;
        }

        if (prescaler <= 256) {
                psr = 0;
                sps = prescaler - 1;
        } else {
                psr = 256 - 1;
                sps = prescaler / 256 - 1;
        }

        spin_lock_irqsave(&gtm->lock, flags);

        /*
         * Properly reset timers: stop, reset, set up prescalers, reference
         * value and clear event register.
         */
        clrsetbits_8(tmr->gtcfr, ~(GTCFR_STP(num) | GTCFR_RST(num)),
                                 GTCFR_STP(num) | GTCFR_RST(num));

        setbits8(tmr->gtcfr, GTCFR_STP(num));

        if (tmr->gtpsr)
                out_be16(tmr->gtpsr, psr);
        clrsetbits_be16(tmr->gtmdr, 0xFFFF, iclk | GTMDR_SPS(sps) |
                        GTMDR_ORI | (free_run ? GTMDR_FRR : 0));
        out_be16(tmr->gtcnr, 0);
        out_be16(tmr->gtrfr, reference_value);
        out_be16(tmr->gtevr, 0xFFFF);

        /* Let it be. */
        clrbits8(tmr->gtcfr, GTCFR_STP(num));

        spin_unlock_irqrestore(&gtm->lock, flags);

        return 0;
}

/**
 * gtm_set_timer16 - (re)set 16 bit timer with arbitrary precision
 * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
 * @usec:       timer interval in microseconds
 * @reload:     if set, the timer will reset upon expiry rather than
 *              continue running free.
 * Context:     any
 *
 * This function (re)sets the GTM timer so that it counts up to the requested
 * interval value, and fires the interrupt when the value is reached. This
 * function will reduce the precision of the timer as needed in order for the
 * requested timeout to fit in a 16-bit register.
 */
int gtm_set_timer16(struct gtm_timer *tmr, unsigned long usec, bool reload)
{
        /* quite obvious, frequency which is enough for µSec precision */
        int freq = 1000000;
        unsigned int bit;

        bit = fls_long(usec);
        if (bit > 15) {
                freq >>= bit - 15;
                usec >>= bit - 15;
        }

        if (!freq)
                return -EINVAL;

        return gtm_set_ref_timer16(tmr, freq, usec, reload);
}
EXPORT_SYMBOL(gtm_set_timer16);

/**
 * gtm_set_exact_utimer16 - (re)set 16 bits timer
 * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
 * @usec:       timer interval in microseconds
 * @reload:     if set, the timer will reset upon expiry rather than
 *              continue running free.
 * Context:     any
 *
 * This function (re)sets GTM timer so that it counts up to the requested
 * interval value, and fires the interrupt when the value is reached. If reload
 * flag was set, timer will also reset itself upon reference value, otherwise
 * it continues to increment.
 *
 * The _exact_ bit in the function name states that this function will not
 * crop precision of the "usec" argument, thus usec is limited to 16 bits
 * (single timer width).
 */
int gtm_set_exact_timer16(struct gtm_timer *tmr, u16 usec, bool reload)
{
        /* quite obvious, frequency which is enough for µSec precision */
        const int freq = 1000000;

        /*
         * We can lower the frequency (and probably power consumption) by
         * dividing both frequency and usec by 2 until there is no remainder.
         * But we won't bother with this unless savings are measured, so just
         * run the timer as is.
         */

        return gtm_set_ref_timer16(tmr, freq, usec, reload);
}
EXPORT_SYMBOL(gtm_set_exact_timer16);

/**
 * gtm_stop_timer16 - stop single timer
 * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
 * Context:     any
 *
 * This function simply stops the GTM timer.
 */
void gtm_stop_timer16(struct gtm_timer *tmr)
{
        struct gtm *gtm = tmr->gtm;
        int num = tmr - &gtm->timers[0];
        unsigned long flags;

        spin_lock_irqsave(&gtm->lock, flags);

        setbits8(tmr->gtcfr, GTCFR_STP(num));
        out_be16(tmr->gtevr, 0xFFFF);

        spin_unlock_irqrestore(&gtm->lock, flags);
}
EXPORT_SYMBOL(gtm_stop_timer16);

/**
 * gtm_ack_timer16 - acknowledge timer event (free-run timers only)
 * @tmr:        pointer to the gtm_timer structure obtained from gtm_get_timer
 * @events:     events mask to ack
 * Context:     any
 *
 * Thus function used to acknowledge timer interrupt event, use it inside the
 * interrupt handler.
 */
void gtm_ack_timer16(struct gtm_timer *tmr, u16 events)
{
        out_be16(tmr->gtevr, events);
}
EXPORT_SYMBOL(gtm_ack_timer16);

static void __init gtm_set_shortcuts(struct device_node *np,
                                     struct gtm_timer *timers,
                                     struct gtm_timers_regs __iomem *regs)
{
        /*
         * Yeah, I don't like this either, but timers' registers a bit messed,
         * so we have to provide shortcuts to write timer independent code.
         * Alternative option is to create gt*() accessors, but that will be
         * even uglier and cryptic.
         */
        timers[0].gtcfr = &regs->gtcfr1;
        timers[0].gtmdr = &regs->gtmdr1;
        timers[0].gtcnr = &regs->gtcnr1;
        timers[0].gtrfr = &regs->gtrfr1;
        timers[0].gtevr = &regs->gtevr1;

        timers[1].gtcfr = &regs->gtcfr1;
        timers[1].gtmdr = &regs->gtmdr2;
        timers[1].gtcnr = &regs->gtcnr2;
        timers[1].gtrfr = &regs->gtrfr2;
        timers[1].gtevr = &regs->gtevr2;

        timers[2].gtcfr = &regs->gtcfr2;
        timers[2].gtmdr = &regs->gtmdr3;
        timers[2].gtcnr = &regs->gtcnr3;
        timers[2].gtrfr = &regs->gtrfr3;
        timers[2].gtevr = &regs->gtevr3;

        timers[3].gtcfr = &regs->gtcfr2;
        timers[3].gtmdr = &regs->gtmdr4;
        timers[3].gtcnr = &regs->gtcnr4;
        timers[3].gtrfr = &regs->gtrfr4;
        timers[3].gtevr = &regs->gtevr4;

        /* CPM2 doesn't have primary prescaler */
        if (!of_device_is_compatible(np, "fsl,cpm2-gtm")) {
                timers[0].gtpsr = &regs->gtpsr1;
                timers[1].gtpsr = &regs->gtpsr2;
                timers[2].gtpsr = &regs->gtpsr3;
                timers[3].gtpsr = &regs->gtpsr4;
        }
}

static int __init fsl_gtm_init(void)
{
        struct device_node *np;

        for_each_compatible_node(np, NULL, "fsl,gtm") {
                int i;
                struct gtm *gtm;
                const u32 *clock;
                int size;

                gtm = kzalloc(sizeof(*gtm), GFP_KERNEL);
                if (!gtm) {
                        pr_err("%pOF: unable to allocate memory\n",
                                np);
                        continue;
                }

                spin_lock_init(&gtm->lock);

                clock = of_get_property(np, "clock-frequency", &size);
                if (!clock || size != sizeof(*clock)) {
                        pr_err("%pOF: no clock-frequency\n", np);
                        goto err;
                }
                gtm->clock = *clock;

                for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
                        unsigned int irq;

                        irq = irq_of_parse_and_map(np, i);
                        if (!irq) {
                                pr_err("%pOF: not enough interrupts specified\n",
                                       np);
                                goto err;
                        }
                        gtm->timers[i].irq = irq;
                        gtm->timers[i].gtm = gtm;
                }

                gtm->regs = of_iomap(np, 0);
                if (!gtm->regs) {
                        pr_err("%pOF: unable to iomap registers\n",
                               np);
                        goto err;
                }

                gtm_set_shortcuts(np, gtm->timers, gtm->regs);
                list_add(&gtm->list_node, &gtms);

                /* We don't want to lose the node and its ->data */
                np->data = gtm;
                of_node_get(np);

                continue;
err:
                kfree(gtm);
        }
        return 0;
}
arch_initcall(fsl_gtm_init);