/*
 * Copyright 2008 Freescale Semiconductor, Inc.
 *
 * 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.
 */

#include <common.h>
#include <asm/fsl_ddr_sdram.h>

#include "ddr.h"

/*
 * Calculate the Density of each Physical Rank.
 * Returned size is in bytes.
 *
 * Study these table from Byte 31 of JEDEC SPD Spec.
 *
 *              DDR I   DDR II
 *      Bit     Size    Size
 *      ---     -----   ------
 *      7 high  512MB   512MB
 *      6       256MB   256MB
 *      5       128MB   128MB
 *      4        64MB    16GB
 *      3        32MB     8GB
 *      2        16MB     4GB
 *      1         2GB     2GB
 *      0 low     1GB     1GB
 *
 * Reorder Table to be linear by stripping the bottom
 * 2 or 5 bits off and shifting them up to the top.
 */

static unsigned long long
compute_ranksize(unsigned int mem_type, unsigned char row_dens)
{
        unsigned long long bsize;

        /* Bottom 2 bits up to the top. */
        bsize = ((row_dens >> 2) | ((row_dens & 3) << 6));
        bsize <<= 24ULL;
        debug("DDR: DDR I rank density = 0x%08x\n", bsize);

        return bsize;
}

/*
 * Convert a two-nibble BCD value into a cycle time.
 * While the spec calls for nano-seconds, picos are returned.
 *
 * This implements the tables for bytes 9, 23 and 25 for both
 * DDR I and II.  No allowance for distinguishing the invalid
 * fields absent for DDR I yet present in DDR II is made.
 * (That is, cycle times of .25, .33, .66 and .75 ns are
 * allowed for both DDR II and I.)
 */
static unsigned int
convert_bcd_tenths_to_cycle_time_ps(unsigned int spd_val)
{
        /* Table look up the lower nibble, allow DDR I & II. */
        unsigned int tenths_ps[16] = {
                0,
                100,
                200,
                300,
                400,
                500,
                600,
                700,
                800,
                900,
                250,    /* This and the next 3 entries valid ... */
                330,    /* ...  only for tCK calculations. */
                660,
                750,
                0,      /* undefined */
                0       /* undefined */
        };

        unsigned int whole_ns = (spd_val & 0xF0) >> 4;
        unsigned int tenth_ns = spd_val & 0x0F;
        unsigned int ps = whole_ns * 1000 + tenths_ps[tenth_ns];

        return ps;
}

static unsigned int
convert_bcd_hundredths_to_cycle_time_ps(unsigned int spd_val)
{
        unsigned int tenth_ns = (spd_val & 0xF0) >> 4;
        unsigned int hundredth_ns = spd_val & 0x0F;
        unsigned int ps = tenth_ns * 100 + hundredth_ns * 10;

        return ps;
}

static unsigned int byte40_table_ps[8] = {
        0,
        250,
        330,
        500,
        660,
        750,
        0,      /* supposed to be RFC, but not sure what that means */
        0       /* Undefined */
};

static unsigned int
compute_trfc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trfc)
{
        unsigned int trfc_ps;

        trfc_ps = (((trctrfc_ext & 0x1) * 256) + trfc) * 1000
                + byte40_table_ps[(trctrfc_ext >> 1) & 0x7];

        return trfc_ps;
}

static unsigned int
compute_trc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trc)
{
        unsigned int trc_ps;

        trc_ps = trc * 1000 + byte40_table_ps[(trctrfc_ext >> 4) & 0x7];

        return trc_ps;
}

/*
 * tCKmax from DDR I SPD Byte 43
 *
 * Bits 7:2 == whole ns
 * Bits 1:0 == quarter ns
 *    00    == 0.00 ns
 *    01    == 0.25 ns
 *    10    == 0.50 ns
 *    11    == 0.75 ns
 *
 * Returns picoseconds.
 */
static unsigned int
compute_tckmax_from_spd_ps(unsigned int byte43)
{
        return (byte43 >> 2) * 1000 + (byte43 & 0x3) * 250;
}

/*
 * Determine Refresh Rate.  Ignore self refresh bit on DDR I.
 * Table from SPD Spec, Byte 12, converted to picoseconds and
 * filled in with "default" normal values.
 */
static unsigned int
determine_refresh_rate_ps(const unsigned int spd_refresh)
{
        unsigned int refresh_time_ps[8] = {
                15625000,       /* 0 Normal    1.00x */
                3900000,        /* 1 Reduced    .25x */
                7800000,        /* 2 Extended   .50x */
                31300000,       /* 3 Extended  2.00x */
                62500000,       /* 4 Extended  4.00x */
                125000000,      /* 5 Extended  8.00x */
                15625000,       /* 6 Normal    1.00x  filler */
                15625000,       /* 7 Normal    1.00x  filler */
        };

        return refresh_time_ps[spd_refresh & 0x7];
}

/*
 * The purpose of this function is to compute a suitable
 * CAS latency given the DRAM clock period.  The SPD only
 * defines at most 3 CAS latencies.  Typically the slower in
 * frequency the DIMM runs at, the shorter its CAS latency can be.
 * If the DIMM is operating at a sufficiently low frequency,
 * it may be able to run at a CAS latency shorter than the
 * shortest SPD-defined CAS latency.
 *
 * If a CAS latency is not found, 0 is returned.
 *
 * Do this by finding in the standard speed bin table the longest
 * tCKmin that doesn't exceed the value of mclk_ps (tCK).
 *
 * An assumption made is that the SDRAM device allows the
 * CL to be programmed for a value that is lower than those
 * advertised by the SPD.  This is not always the case,
 * as those modes not defined in the SPD are optional.
 *
 * CAS latency de-rating based upon values JEDEC Standard No. 79-E
 * Table 11.
 *
 * ordinal 2, ddr1_speed_bins[1] contains tCK for CL=2
 */
                                  /*   CL2.0 CL2.5 CL3.0  */
unsigned short ddr1_speed_bins[] = {0, 7500, 6000, 5000 };

unsigned int
compute_derated_DDR1_CAS_latency(unsigned int mclk_ps)
{
        const unsigned int num_speed_bins = ARRAY_SIZE(ddr1_speed_bins);
        unsigned int lowest_tCKmin_found = 0;
        unsigned int lowest_tCKmin_CL = 0;
        unsigned int i;

        debug("mclk_ps = %u\n", mclk_ps);

        for (i = 0; i < num_speed_bins; i++) {
                unsigned int x = ddr1_speed_bins[i];
                debug("i=%u, x = %u, lowest_tCKmin_found = %u\n",
                      i, x, lowest_tCKmin_found);
                if (x && lowest_tCKmin_found <= x && x <= mclk_ps) {
                        lowest_tCKmin_found = x;
                        lowest_tCKmin_CL = i + 1;
                }
        }

        debug("lowest_tCKmin_CL = %u\n", lowest_tCKmin_CL);

        return lowest_tCKmin_CL;
}

/*
 * ddr_compute_dimm_parameters for DDR1 SPD
 *
 * Compute DIMM parameters based upon the SPD information in spd.
 * Writes the results to the dimm_params_t structure pointed by pdimm.
 *
 * FIXME: use #define for the retvals
 */
unsigned int
ddr_compute_dimm_parameters(const ddr1_spd_eeprom_t *spd,
                             dimm_params_t *pdimm,
                             unsigned int dimm_number)
{
        unsigned int retval;

        if (spd->mem_type) {
                if (spd->mem_type != SPD_MEMTYPE_DDR) {
                        printf("DIMM %u: is not a DDR1 SPD.\n", dimm_number);
                        return 1;
                }
        } else {
                memset(pdimm, 0, sizeof(dimm_params_t));
                return 1;
        }

        retval = ddr1_spd_check(spd);
        if (retval) {
                printf("DIMM %u: failed checksum\n", dimm_number);
                return 2;
        }

        /*
         * The part name in ASCII in the SPD EEPROM is not null terminated.
         * Guarantee null termination here by presetting all bytes to 0
         * and copying the part name in ASCII from the SPD onto it
         */
        memset(pdimm->mpart, 0, sizeof(pdimm->mpart));
        memcpy(pdimm->mpart, spd->mpart, sizeof(pdimm->mpart) - 1);

        /* DIMM organization parameters */
        pdimm->n_ranks = spd->nrows;
        pdimm->rank_density = compute_ranksize(spd->mem_type, spd->bank_dens);
        pdimm->capacity = pdimm->n_ranks * pdimm->rank_density;
        pdimm->data_width = spd->dataw_lsb;
        pdimm->primary_sdram_width = spd->primw;
        pdimm->ec_sdram_width = spd->ecw;

        /*
         * FIXME: Need to determine registered_dimm status.
         *     1 == register buffered
         *     0 == unbuffered
         */
        pdimm->registered_dimm = 0;     /* unbuffered */

        /* SDRAM device parameters */
        pdimm->n_row_addr = spd->nrow_addr;
        pdimm->n_col_addr = spd->ncol_addr;
        pdimm->n_banks_per_sdram_device = spd->nbanks;
        pdimm->edc_config = spd->config;
        pdimm->burst_lengths_bitmask = spd->burstl;
        pdimm->row_density = spd->bank_dens;

        /*
         * Calculate the Maximum Data Rate based on the Minimum Cycle time.
         * The SPD clk_cycle field (tCKmin) is measured in tenths of
         * nanoseconds and represented as BCD.
         */
        pdimm->tCKmin_X_ps
                = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle);
        pdimm->tCKmin_X_minus_1_ps
                = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle2);
        pdimm->tCKmin_X_minus_2_ps
                = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle3);

        pdimm->tCKmax_ps = compute_tckmax_from_spd_ps(spd->tckmax);

        /*
         * Compute CAS latencies defined by SPD
         * The SPD caslat_X should have at least 1 and at most 3 bits set.
         *
         * If cas_lat after masking is 0, the __ilog2 function returns
         * 255 into the variable.   This behavior is abused once.
         */
        pdimm->caslat_X  = __ilog2(spd->cas_lat);
        pdimm->caslat_X_minus_1 = __ilog2(spd->cas_lat
                                          & ~(1 << pdimm->caslat_X));
        pdimm->caslat_X_minus_2 = __ilog2(spd->cas_lat
                                          & ~(1 << pdimm->caslat_X)
                                          & ~(1 << pdimm->caslat_X_minus_1));

        /* Compute CAS latencies below that defined by SPD */
        pdimm->caslat_lowest_derated
                = compute_derated_DDR1_CAS_latency(get_memory_clk_period_ps());

        /* Compute timing parameters */
        pdimm->tRCD_ps = spd->trcd * 250;
        pdimm->tRP_ps = spd->trp * 250;
        pdimm->tRAS_ps = spd->tras * 1000;

        pdimm->tWR_ps = mclk_to_picos(3);
        pdimm->tWTR_ps = mclk_to_picos(1);
        pdimm->tRFC_ps = compute_trfc_ps_from_spd(0, spd->trfc);

        pdimm->tRRD_ps = spd->trrd * 250;
        pdimm->tRC_ps = compute_trc_ps_from_spd(0, spd->trc);

        pdimm->refresh_rate_ps = determine_refresh_rate_ps(spd->refresh);

        pdimm->tIS_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_setup);
        pdimm->tIH_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_hold);
        pdimm->tDS_ps
                = convert_bcd_hundredths_to_cycle_time_ps(spd->data_setup);
        pdimm->tDH_ps
                = convert_bcd_hundredths_to_cycle_time_ps(spd->data_hold);

        pdimm->tRTP_ps = mclk_to_picos(2);      /* By the book. */
        pdimm->tDQSQ_max_ps = spd->tdqsq * 10;
        pdimm->tQHS_ps = spd->tqhs * 10;

        return 0;
}