diff options
Diffstat (limited to 'arch/ppc/cpu/mpc8xxx/ddr/ddr2_dimm_params.c')
| -rw-r--r-- | arch/ppc/cpu/mpc8xxx/ddr/ddr2_dimm_params.c | 339 |
1 files changed, 339 insertions, 0 deletions
diff --git a/arch/ppc/cpu/mpc8xxx/ddr/ddr2_dimm_params.c b/arch/ppc/cpu/mpc8xxx/ddr/ddr2_dimm_params.c new file mode 100644 index 000000000..d9d0fa70e --- /dev/null +++ b/arch/ppc/cpu/mpc8xxx/ddr/ddr2_dimm_params.c @@ -0,0 +1,339 @@ +/* + * 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 5 bits up to the top. */ + bsize = ((row_dens >> 5) | ((row_dens & 31) << 3)); + bsize <<= 27ULL; + debug("DDR: DDR II 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; +} + +/* + * 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. 79-2C + * Table 40, "DDR2 SDRAM stanadard speed bins and tCK, tRCD, tRP, tRAS, + * and tRC for corresponding bin" + * + * ordinal 2, ddr2_speed_bins[1] contains tCK for CL=3 + * Not certain if any good value exists for CL=2 + */ + /* CL2 CL3 CL4 CL5 CL6 */ +unsigned short ddr2_speed_bins[] = { 0, 5000, 3750, 3000, 2500 }; + +unsigned int +compute_derated_DDR2_CAS_latency(unsigned int mclk_ps) +{ + const unsigned int num_speed_bins = ARRAY_SIZE(ddr2_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 = ddr2_speed_bins[i]; + debug("i=%u, x = %u, lowest_tCKmin_found = %u\n", + i, x, lowest_tCKmin_found); + if (x && x <= mclk_ps && x >= lowest_tCKmin_found ) { + lowest_tCKmin_found = x; + lowest_tCKmin_CL = i + 2; + } + } + + debug("lowest_tCKmin_CL = %u\n", lowest_tCKmin_CL); + + return lowest_tCKmin_CL; +} + +/* + * ddr_compute_dimm_parameters for DDR2 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 ddr2_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_DDR2) { + printf("DIMM %u: is not a DDR2 SPD.\n", dimm_number); + return 1; + } + } else { + memset(pdimm, 0, sizeof(dimm_params_t)); + return 1; + } + + retval = ddr2_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->mod_ranks & 0x7) + 1; + pdimm->rank_density = compute_ranksize(spd->mem_type, spd->rank_dens); + pdimm->capacity = pdimm->n_ranks * pdimm->rank_density; + pdimm->data_width = spd->dataw; + pdimm->primary_sdram_width = spd->primw; + pdimm->ec_sdram_width = spd->ecw; + + /* FIXME: what about registered SO-DIMM? */ + switch (spd->dimm_type) { + case 0x01: /* RDIMM */ + case 0x10: /* Mini-RDIMM */ + pdimm->registered_dimm = 1; /* register buffered */ + break; + + case 0x02: /* UDIMM */ + case 0x04: /* SO-DIMM */ + case 0x08: /* Micro-DIMM */ + case 0x20: /* Mini-UDIMM */ + pdimm->registered_dimm = 0; /* unbuffered */ + break; + + default: + printf("unknown dimm_type 0x%02X\n", spd->dimm_type); + return 1; + break; + } + + /* 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->rank_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 = convert_bcd_tenths_to_cycle_time_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_DDR2_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 = spd->twr * 250; + pdimm->tWTR_ps = spd->twtr * 250; + pdimm->tRFC_ps = compute_trfc_ps_from_spd(spd->trctrfc_ext, spd->trfc); + + pdimm->tRRD_ps = spd->trrd * 250; + pdimm->tRC_ps = compute_trc_ps_from_spd(spd->trctrfc_ext, 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 = spd->trtp * 250; + pdimm->tDQSQ_max_ps = spd->tdqsq * 10; + pdimm->tQHS_ps = spd->tqhs * 10; + + return 0; +} |