/*
 *  linux/arch/arm/mach-sa1100/cpu-sa1110.c
 *
 *  Copyright (C) 2001 Russell King
 *
 *  $Id: cpu-sa1110.c,v 1.9 2002/07/06 16:53:18 rmk Exp $
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Note: there are two erratas that apply to the SA1110 here:
 *  7 - SDRAM auto-power-up failure (rev A0)
 * 13 - Corruption of internal register reads/writes following
 *      SDRAM reads (rev A0, B0, B1)
 *
 * We ignore rev. A0 and B0 devices; I don't think they're worth supporting.
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/init.h>

#include <asm/hardware.h>
#include <asm/mach-types.h>
#include <asm/io.h>
#include <asm/system.h>

#include "generic.h"

#undef DEBUG

static struct cpufreq_driver sa1110_driver;

struct sdram_params {
        u_char  rows;           /* bits                          */
        u_char  cas_latency;    /* cycles                        */
        u_char  tck;            /* clock cycle time (ns)         */
        u_char  trcd;           /* activate to r/w (ns)          */
        u_char  trp;            /* precharge to activate (ns)    */
        u_char  twr;            /* write recovery time (ns)      */
        u_short refresh;        /* refresh time for array (us)   */
};

struct sdram_info {
        u_int   mdcnfg;
        u_int   mdrefr;
        u_int   mdcas[3];
};

static struct sdram_params tc59sm716_cl2_params __initdata = {
        .rows                   = 12,
        .tck                    = 10,
        .trcd                   = 20,
        .trp                    = 20,
        .twr                    = 10,
        .refresh                = 64000,
        .cas_latency            = 2,
};

static struct sdram_params tc59sm716_cl3_params __initdata = {
        .rows                   = 12,
        .tck                    = 8,
        .trcd                   = 20,
        .trp                    = 20,
        .twr                    = 8,
        .refresh                = 64000,
        .cas_latency            = 3,
};

static struct sdram_params samsung_k4s641632d_tc75 __initdata = {
        .rows                   = 14,
        .tck                    = 9,
        .trcd                   = 27,
        .trp                    = 20,
        .twr                    = 9,
        .refresh                = 64000,
        .cas_latency            = 3,
};

static struct sdram_params samsung_km416s4030ct __initdata = {
        .rows                   = 13,
        .tck                    = 8,
        .trcd                   = 24,   /* 3 CLKs */
        .trp                    = 24,   /* 3 CLKs */
        .twr                    = 16,   /* Trdl: 2 CLKs */
        .refresh                = 64000,
        .cas_latency            = 3,
};

static struct sdram_params wbond_w982516ah75l_cl3_params __initdata = {
        .rows                   = 16,
        .tck                    = 8,
        .trcd                   = 20,
        .trp                    = 20,
        .twr                    = 8,
        .refresh                = 64000,
        .cas_latency            = 3,
};

static struct sdram_params sdram_params;

/*
 * Given a period in ns and frequency in khz, calculate the number of
 * cycles of frequency in period.  Note that we round up to the next
 * cycle, even if we are only slightly over.
 */
static inline u_int ns_to_cycles(u_int ns, u_int khz)
{
        return (ns * khz + 999999) / 1000000;
}

/*
 * Create the MDCAS register bit pattern.
 */
static inline void set_mdcas(u_int *mdcas, int delayed, u_int rcd)
{
        u_int shift;

        rcd = 2 * rcd - 1;
        shift = delayed + 1 + rcd;

        mdcas[0]  = (1 << rcd) - 1;
        mdcas[0] |= 0x55555555 << shift;
        mdcas[1]  = mdcas[2] = 0x55555555 << (shift & 1);
}

static void
sdram_calculate_timing(struct sdram_info *sd, u_int cpu_khz,
                       struct sdram_params *sdram)
{
        u_int mem_khz, sd_khz, trp, twr;

        mem_khz = cpu_khz / 2;
        sd_khz = mem_khz;

        /*
         * If SDCLK would invalidate the SDRAM timings,
         * run SDCLK at half speed.
         *
         * CPU steppings prior to B2 must either run the memory at
         * half speed or use delayed read latching (errata 13).
         */
        if ((ns_to_cycles(sdram->tck, sd_khz) > 1) ||
            (CPU_REVISION < CPU_SA1110_B2 && sd_khz < 62000))
                sd_khz /= 2;

        sd->mdcnfg = MDCNFG & 0x007f007f;

        twr = ns_to_cycles(sdram->twr, mem_khz);

        /* trp should always be >1 */
        trp = ns_to_cycles(sdram->trp, mem_khz) - 1;
        if (trp < 1)
                trp = 1;

        sd->mdcnfg |= trp << 8;
        sd->mdcnfg |= trp << 24;
        sd->mdcnfg |= sdram->cas_latency << 12;
        sd->mdcnfg |= sdram->cas_latency << 28;
        sd->mdcnfg |= twr << 14;
        sd->mdcnfg |= twr << 30;

        sd->mdrefr = MDREFR & 0xffbffff0;
        sd->mdrefr |= 7;

        if (sd_khz != mem_khz)
                sd->mdrefr |= MDREFR_K1DB2;

        /* initial number of '1's in MDCAS + 1 */
        set_mdcas(sd->mdcas, sd_khz >= 62000, ns_to_cycles(sdram->trcd, mem_khz));

#ifdef DEBUG
        printk("MDCNFG: %08x MDREFR: %08x MDCAS0: %08x MDCAS1: %08x MDCAS2: %08x\n",
                sd->mdcnfg, sd->mdrefr, sd->mdcas[0], sd->mdcas[1], sd->mdcas[2]);
#endif
}

/*
 * Set the SDRAM refresh rate.
 */
static inline void sdram_set_refresh(u_int dri)
{
        MDREFR = (MDREFR & 0xffff000f) | (dri << 4);
        (void) MDREFR;
}

/*
 * Update the refresh period.  We do this such that we always refresh
 * the SDRAMs within their permissible period.  The refresh period is
 * always a multiple of the memory clock (fixed at cpu_clock / 2).
 *
 * FIXME: we don't currently take account of burst accesses here,
 * but neither do Intels DM nor Angel.
 */
static void
sdram_update_refresh(u_int cpu_khz, struct sdram_params *sdram)
{
        u_int ns_row = (sdram->refresh * 1000) >> sdram->rows;
        u_int dri = ns_to_cycles(ns_row, cpu_khz / 2) / 32;

#ifdef DEBUG
        mdelay(250);
        printk("new dri value = %d\n", dri);
#endif

        sdram_set_refresh(dri);
}

/*
 * Ok, set the CPU frequency.  
 */
static int sa1110_target(struct cpufreq_policy *policy,
                         unsigned int target_freq,
                         unsigned int relation)
{
        struct sdram_params *sdram = &sdram_params;
        struct cpufreq_freqs freqs;
        struct sdram_info sd;
        unsigned long flags;
        unsigned int ppcr, unused;

        switch(relation){
        case CPUFREQ_RELATION_L:
                ppcr = sa11x0_freq_to_ppcr(target_freq);
                if (sa11x0_ppcr_to_freq(ppcr) > policy->max)
                        ppcr--;
                break;
        case CPUFREQ_RELATION_H:
                ppcr = sa11x0_freq_to_ppcr(target_freq);
                if (ppcr && (sa11x0_ppcr_to_freq(ppcr) > target_freq) &&
                    (sa11x0_ppcr_to_freq(ppcr-1) >= policy->min))
                        ppcr--;
                break;
        default:
                return -EINVAL;
        }

        freqs.old = sa11x0_getspeed(0);
        freqs.new = sa11x0_ppcr_to_freq(ppcr);
        freqs.cpu = 0;

        sdram_calculate_timing(&sd, freqs.new, sdram);

#if 0
        /*
         * These values are wrong according to the SA1110 documentation
         * and errata, but they seem to work.  Need to get a storage
         * scope on to the SDRAM signals to work out why.
         */
        if (policy->max < 147500) {
                sd.mdrefr |= MDREFR_K1DB2;
                sd.mdcas[0] = 0xaaaaaa7f;
        } else {
                sd.mdrefr &= ~MDREFR_K1DB2;
                sd.mdcas[0] = 0xaaaaaa9f;
        }
        sd.mdcas[1] = 0xaaaaaaaa;
        sd.mdcas[2] = 0xaaaaaaaa;
#endif

        cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

        /*
         * The clock could be going away for some time.  Set the SDRAMs
         * to refresh rapidly (every 64 memory clock cycles).  To get
         * through the whole array, we need to wait 262144 mclk cycles.
         * We wait 20ms to be safe.
         */
        sdram_set_refresh(2);
        if (!irqs_disabled()) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(20 * HZ / 1000);
        } else {
                mdelay(20);
        }

        /*
         * Reprogram the DRAM timings with interrupts disabled, and
         * ensure that we are doing this within a complete cache line.
         * This means that we won't access SDRAM for the duration of
         * the programming.
         */
        local_irq_save(flags);
        asm("mcr p15, 0, %0, c7, c10, 4" : : "r" (0));
        udelay(10);
        __asm__ __volatile__("                                  \n\
                b       2f                                      \n\
                .align  5                                       \n\
1:              str     %3, [%1, #0]            @ MDCNFG        \n\
                str     %4, [%1, #28]           @ MDREFR        \n\
                str     %5, [%1, #4]            @ MDCAS0        \n\
                str     %6, [%1, #8]            @ MDCAS1        \n\
                str     %7, [%1, #12]           @ MDCAS2        \n\
                str     %8, [%2, #0]            @ PPCR          \n\
                ldr     %0, [%1, #0]                            \n\
                b       3f                                      \n\
2:              b       1b                                      \n\
3:              nop                                             \n\
                nop"
                : "=&r" (unused)
                : "r" (&MDCNFG), "r" (&PPCR), "0" (sd.mdcnfg),
                  "r" (sd.mdrefr), "r" (sd.mdcas[0]),
                  "r" (sd.mdcas[1]), "r" (sd.mdcas[2]), "r" (ppcr));
        local_irq_restore(flags);

        /*
         * Now, return the SDRAM refresh back to normal.
         */
        sdram_update_refresh(freqs.new, sdram);

        cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

        return 0;
}

static int __init sa1110_cpu_init(struct cpufreq_policy *policy)
{
        if (policy->cpu != 0)
                return -EINVAL;
        policy->cur = policy->min = policy->max = sa11x0_getspeed(0);
        policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
        policy->cpuinfo.min_freq = 59000;
        policy->cpuinfo.max_freq = 287000;
        policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
        return 0;
}

static struct cpufreq_driver sa1110_driver = {
        .flags          = CPUFREQ_STICKY |
                          CPUFREQ_PANIC_OUTOFSYNC | 
                          CPUFREQ_PANIC_RESUME_OUTOFSYNC,
        .verify         = sa11x0_verify_speed,
        .target         = sa1110_target,
        .get            = sa11x0_getspeed,
        .init           = sa1110_cpu_init,
        .name           = "sa1110",
};

static int __init sa1110_clk_init(void)
{
        struct sdram_params *sdram = NULL;

        if (machine_is_assabet())
                sdram = &tc59sm716_cl3_params;

        if (machine_is_pt_system3())
                sdram = &samsung_k4s641632d_tc75;

        if (machine_is_h3100())
                sdram = &samsung_km416s4030ct;

        if (sdram) {
                printk(KERN_DEBUG "SDRAM: tck: %d trcd: %d trp: %d"
                        " twr: %d refresh: %d cas_latency: %d\n",
                        sdram->tck, sdram->trcd, sdram->trp,
                        sdram->twr, sdram->refresh, sdram->cas_latency);

                memcpy(&sdram_params, sdram, sizeof(sdram_params));

                return cpufreq_register_driver(&sa1110_driver);
        }

        return 0;
}

arch_initcall(sa1110_clk_init);