u-boot/cpu/mpc8xxx/ddr/ddr1_dimm_params.c

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/*
* 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;
}