2 * Copyright 2008 Freescale Semiconductor, Inc.
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * Version 2 as published by the Free Software Foundation.
10 #include <fsl_ddr_sdram.h>
15 * Calculate the Density of each Physical Rank.
16 * Returned size is in bytes.
18 * Study these table from Byte 31 of JEDEC SPD Spec.
32 * Reorder Table to be linear by stripping the bottom
33 * 2 or 5 bits off and shifting them up to the top.
36 static unsigned long long
37 compute_ranksize(unsigned int mem_type, unsigned char row_dens)
39 unsigned long long bsize;
41 /* Bottom 2 bits up to the top. */
42 bsize = ((row_dens >> 2) | ((row_dens & 3) << 6));
44 debug("DDR: DDR I rank density = 0x%16llx\n", bsize);
50 * Convert a two-nibble BCD value into a cycle time.
51 * While the spec calls for nano-seconds, picos are returned.
53 * This implements the tables for bytes 9, 23 and 25 for both
54 * DDR I and II. No allowance for distinguishing the invalid
55 * fields absent for DDR I yet present in DDR II is made.
56 * (That is, cycle times of .25, .33, .66 and .75 ns are
57 * allowed for both DDR II and I.)
60 convert_bcd_tenths_to_cycle_time_ps(unsigned int spd_val)
62 /* Table look up the lower nibble, allow DDR I & II. */
63 unsigned int tenths_ps[16] = {
74 250, /* This and the next 3 entries valid ... */
75 330, /* ... only for tCK calculations. */
82 unsigned int whole_ns = (spd_val & 0xF0) >> 4;
83 unsigned int tenth_ns = spd_val & 0x0F;
84 unsigned int ps = whole_ns * 1000 + tenths_ps[tenth_ns];
90 convert_bcd_hundredths_to_cycle_time_ps(unsigned int spd_val)
92 unsigned int tenth_ns = (spd_val & 0xF0) >> 4;
93 unsigned int hundredth_ns = spd_val & 0x0F;
94 unsigned int ps = tenth_ns * 100 + hundredth_ns * 10;
99 static unsigned int byte40_table_ps[8] = {
106 0, /* supposed to be RFC, but not sure what that means */
111 compute_trfc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trfc)
113 unsigned int trfc_ps;
115 trfc_ps = (((trctrfc_ext & 0x1) * 256) + trfc) * 1000
116 + byte40_table_ps[(trctrfc_ext >> 1) & 0x7];
122 compute_trc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trc)
126 trc_ps = trc * 1000 + byte40_table_ps[(trctrfc_ext >> 4) & 0x7];
132 * tCKmax from DDR I SPD Byte 43
134 * Bits 7:2 == whole ns
135 * Bits 1:0 == quarter ns
141 * Returns picoseconds.
144 compute_tckmax_from_spd_ps(unsigned int byte43)
146 return (byte43 >> 2) * 1000 + (byte43 & 0x3) * 250;
150 * Determine Refresh Rate. Ignore self refresh bit on DDR I.
151 * Table from SPD Spec, Byte 12, converted to picoseconds and
152 * filled in with "default" normal values.
155 determine_refresh_rate_ps(const unsigned int spd_refresh)
157 unsigned int refresh_time_ps[8] = {
158 15625000, /* 0 Normal 1.00x */
159 3900000, /* 1 Reduced .25x */
160 7800000, /* 2 Extended .50x */
161 31300000, /* 3 Extended 2.00x */
162 62500000, /* 4 Extended 4.00x */
163 125000000, /* 5 Extended 8.00x */
164 15625000, /* 6 Normal 1.00x filler */
165 15625000, /* 7 Normal 1.00x filler */
168 return refresh_time_ps[spd_refresh & 0x7];
172 * The purpose of this function is to compute a suitable
173 * CAS latency given the DRAM clock period. The SPD only
174 * defines at most 3 CAS latencies. Typically the slower in
175 * frequency the DIMM runs at, the shorter its CAS latency can be.
176 * If the DIMM is operating at a sufficiently low frequency,
177 * it may be able to run at a CAS latency shorter than the
178 * shortest SPD-defined CAS latency.
180 * If a CAS latency is not found, 0 is returned.
182 * Do this by finding in the standard speed bin table the longest
183 * tCKmin that doesn't exceed the value of mclk_ps (tCK).
185 * An assumption made is that the SDRAM device allows the
186 * CL to be programmed for a value that is lower than those
187 * advertised by the SPD. This is not always the case,
188 * as those modes not defined in the SPD are optional.
190 * CAS latency de-rating based upon values JEDEC Standard No. 79-E
193 * ordinal 2, ddr1_speed_bins[1] contains tCK for CL=2
195 /* CL2.0 CL2.5 CL3.0 */
196 unsigned short ddr1_speed_bins[] = {0, 7500, 6000, 5000 };
199 compute_derated_DDR1_CAS_latency(unsigned int mclk_ps)
201 const unsigned int num_speed_bins = ARRAY_SIZE(ddr1_speed_bins);
202 unsigned int lowest_tCKmin_found = 0;
203 unsigned int lowest_tCKmin_CL = 0;
206 debug("mclk_ps = %u\n", mclk_ps);
208 for (i = 0; i < num_speed_bins; i++) {
209 unsigned int x = ddr1_speed_bins[i];
210 debug("i=%u, x = %u, lowest_tCKmin_found = %u\n",
211 i, x, lowest_tCKmin_found);
212 if (x && lowest_tCKmin_found <= x && x <= mclk_ps) {
213 lowest_tCKmin_found = x;
214 lowest_tCKmin_CL = i + 1;
218 debug("lowest_tCKmin_CL = %u\n", lowest_tCKmin_CL);
220 return lowest_tCKmin_CL;
224 * ddr_compute_dimm_parameters for DDR1 SPD
226 * Compute DIMM parameters based upon the SPD information in spd.
227 * Writes the results to the dimm_params_t structure pointed by pdimm.
229 * FIXME: use #define for the retvals
232 ddr_compute_dimm_parameters(const ddr1_spd_eeprom_t *spd,
233 dimm_params_t *pdimm,
234 unsigned int dimm_number)
239 if (spd->mem_type != SPD_MEMTYPE_DDR) {
240 printf("DIMM %u: is not a DDR1 SPD.\n", dimm_number);
244 memset(pdimm, 0, sizeof(dimm_params_t));
248 retval = ddr1_spd_check(spd);
250 printf("DIMM %u: failed checksum\n", dimm_number);
255 * The part name in ASCII in the SPD EEPROM is not null terminated.
256 * Guarantee null termination here by presetting all bytes to 0
257 * and copying the part name in ASCII from the SPD onto it
259 memset(pdimm->mpart, 0, sizeof(pdimm->mpart));
260 memcpy(pdimm->mpart, spd->mpart, sizeof(pdimm->mpart) - 1);
262 /* DIMM organization parameters */
263 pdimm->n_ranks = spd->nrows;
264 pdimm->rank_density = compute_ranksize(spd->mem_type, spd->bank_dens);
265 pdimm->capacity = pdimm->n_ranks * pdimm->rank_density;
266 pdimm->data_width = spd->dataw_lsb;
267 pdimm->primary_sdram_width = spd->primw;
268 pdimm->ec_sdram_width = spd->ecw;
271 * FIXME: Need to determine registered_dimm status.
272 * 1 == register buffered
275 pdimm->registered_dimm = 0; /* unbuffered */
277 /* SDRAM device parameters */
278 pdimm->n_row_addr = spd->nrow_addr;
279 pdimm->n_col_addr = spd->ncol_addr;
280 pdimm->n_banks_per_sdram_device = spd->nbanks;
281 pdimm->edc_config = spd->config;
282 pdimm->burst_lengths_bitmask = spd->burstl;
283 pdimm->row_density = spd->bank_dens;
286 * Calculate the Maximum Data Rate based on the Minimum Cycle time.
287 * The SPD clk_cycle field (tCKmin) is measured in tenths of
288 * nanoseconds and represented as BCD.
291 = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle);
292 pdimm->tckmin_x_minus_1_ps
293 = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle2);
294 pdimm->tckmin_x_minus_2_ps
295 = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle3);
297 pdimm->tckmax_ps = compute_tckmax_from_spd_ps(spd->tckmax);
300 * Compute CAS latencies defined by SPD
301 * The SPD caslat_x should have at least 1 and at most 3 bits set.
303 * If cas_lat after masking is 0, the __ilog2 function returns
304 * 255 into the variable. This behavior is abused once.
306 pdimm->caslat_x = __ilog2(spd->cas_lat);
307 pdimm->caslat_x_minus_1 = __ilog2(spd->cas_lat
308 & ~(1 << pdimm->caslat_x));
309 pdimm->caslat_x_minus_2 = __ilog2(spd->cas_lat
310 & ~(1 << pdimm->caslat_x)
311 & ~(1 << pdimm->caslat_x_minus_1));
313 /* Compute CAS latencies below that defined by SPD */
314 pdimm->caslat_lowest_derated
315 = compute_derated_DDR1_CAS_latency(get_memory_clk_period_ps());
317 /* Compute timing parameters */
318 pdimm->trcd_ps = spd->trcd * 250;
319 pdimm->trp_ps = spd->trp * 250;
320 pdimm->tras_ps = spd->tras * 1000;
322 pdimm->twr_ps = mclk_to_picos(3);
323 pdimm->twtr_ps = mclk_to_picos(1);
324 pdimm->trfc_ps = compute_trfc_ps_from_spd(0, spd->trfc);
326 pdimm->trrd_ps = spd->trrd * 250;
327 pdimm->trc_ps = compute_trc_ps_from_spd(0, spd->trc);
329 pdimm->refresh_rate_ps = determine_refresh_rate_ps(spd->refresh);
331 pdimm->tis_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_setup);
332 pdimm->tih_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_hold);
334 = convert_bcd_hundredths_to_cycle_time_ps(spd->data_setup);
336 = convert_bcd_hundredths_to_cycle_time_ps(spd->data_hold);
338 pdimm->trtp_ps = mclk_to_picos(2); /* By the book. */
339 pdimm->tdqsq_max_ps = spd->tdqsq * 10;
340 pdimm->tqhs_ps = spd->tqhs * 10;