1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright 2008 Freescale Semiconductor, Inc.
7 #include <fsl_ddr_sdram.h>
9 #include <asm/bitops.h>
13 * Calculate the Density of each Physical Rank.
14 * Returned size is in bytes.
16 * Study these table from Byte 31 of JEDEC SPD Spec.
30 * Reorder Table to be linear by stripping the bottom
31 * 2 or 5 bits off and shifting them up to the top.
34 static unsigned long long
35 compute_ranksize(unsigned int mem_type, unsigned char row_dens)
37 unsigned long long bsize;
39 /* Bottom 5 bits up to the top. */
40 bsize = ((row_dens >> 5) | ((row_dens & 31) << 3));
42 debug("DDR: DDR II rank density = 0x%16llx\n", bsize);
48 * Convert a two-nibble BCD value into a cycle time.
49 * While the spec calls for nano-seconds, picos are returned.
51 * This implements the tables for bytes 9, 23 and 25 for both
52 * DDR I and II. No allowance for distinguishing the invalid
53 * fields absent for DDR I yet present in DDR II is made.
54 * (That is, cycle times of .25, .33, .66 and .75 ns are
55 * allowed for both DDR II and I.)
58 convert_bcd_tenths_to_cycle_time_ps(unsigned int spd_val)
60 /* Table look up the lower nibble, allow DDR I & II. */
61 unsigned int tenths_ps[16] = {
72 250, /* This and the next 3 entries valid ... */
73 330, /* ... only for tCK calculations. */
80 unsigned int whole_ns = (spd_val & 0xF0) >> 4;
81 unsigned int tenth_ns = spd_val & 0x0F;
82 unsigned int ps = whole_ns * 1000 + tenths_ps[tenth_ns];
88 convert_bcd_hundredths_to_cycle_time_ps(unsigned int spd_val)
90 unsigned int tenth_ns = (spd_val & 0xF0) >> 4;
91 unsigned int hundredth_ns = spd_val & 0x0F;
92 unsigned int ps = tenth_ns * 100 + hundredth_ns * 10;
97 static unsigned int byte40_table_ps[8] = {
104 0, /* supposed to be RFC, but not sure what that means */
109 compute_trfc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trfc)
111 return (((trctrfc_ext & 0x1) * 256) + trfc) * 1000
112 + byte40_table_ps[(trctrfc_ext >> 1) & 0x7];
116 compute_trc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trc)
118 return trc * 1000 + byte40_table_ps[(trctrfc_ext >> 4) & 0x7];
122 * Determine Refresh Rate. Ignore self refresh bit on DDR I.
123 * Table from SPD Spec, Byte 12, converted to picoseconds and
124 * filled in with "default" normal values.
127 determine_refresh_rate_ps(const unsigned int spd_refresh)
129 unsigned int refresh_time_ps[8] = {
130 15625000, /* 0 Normal 1.00x */
131 3900000, /* 1 Reduced .25x */
132 7800000, /* 2 Extended .50x */
133 31300000, /* 3 Extended 2.00x */
134 62500000, /* 4 Extended 4.00x */
135 125000000, /* 5 Extended 8.00x */
136 15625000, /* 6 Normal 1.00x filler */
137 15625000, /* 7 Normal 1.00x filler */
140 return refresh_time_ps[spd_refresh & 0x7];
144 * The purpose of this function is to compute a suitable
145 * CAS latency given the DRAM clock period. The SPD only
146 * defines at most 3 CAS latencies. Typically the slower in
147 * frequency the DIMM runs at, the shorter its CAS latency can.
148 * be. If the DIMM is operating at a sufficiently low frequency,
149 * it may be able to run at a CAS latency shorter than the
150 * shortest SPD-defined CAS latency.
152 * If a CAS latency is not found, 0 is returned.
154 * Do this by finding in the standard speed bin table the longest
155 * tCKmin that doesn't exceed the value of mclk_ps (tCK).
157 * An assumption made is that the SDRAM device allows the
158 * CL to be programmed for a value that is lower than those
159 * advertised by the SPD. This is not always the case,
160 * as those modes not defined in the SPD are optional.
162 * CAS latency de-rating based upon values JEDEC Standard No. 79-2C
163 * Table 40, "DDR2 SDRAM stanadard speed bins and tCK, tRCD, tRP, tRAS,
164 * and tRC for corresponding bin"
166 * ordinal 2, ddr2_speed_bins[1] contains tCK for CL=3
167 * Not certain if any good value exists for CL=2
169 /* CL2 CL3 CL4 CL5 CL6 CL7*/
170 unsigned short ddr2_speed_bins[] = { 0, 5000, 3750, 3000, 2500, 1875 };
173 compute_derated_DDR2_CAS_latency(unsigned int mclk_ps)
175 const unsigned int num_speed_bins = ARRAY_SIZE(ddr2_speed_bins);
176 unsigned int lowest_tCKmin_found = 0;
177 unsigned int lowest_tCKmin_CL = 0;
180 debug("mclk_ps = %u\n", mclk_ps);
182 for (i = 0; i < num_speed_bins; i++) {
183 unsigned int x = ddr2_speed_bins[i];
184 debug("i=%u, x = %u, lowest_tCKmin_found = %u\n",
185 i, x, lowest_tCKmin_found);
186 if (x && x <= mclk_ps && x >= lowest_tCKmin_found ) {
187 lowest_tCKmin_found = x;
188 lowest_tCKmin_CL = i + 2;
192 debug("lowest_tCKmin_CL = %u\n", lowest_tCKmin_CL);
194 return lowest_tCKmin_CL;
198 * ddr_compute_dimm_parameters for DDR2 SPD
200 * Compute DIMM parameters based upon the SPD information in spd.
201 * Writes the results to the dimm_params_t structure pointed by pdimm.
203 * FIXME: use #define for the retvals
205 unsigned int ddr_compute_dimm_parameters(const unsigned int ctrl_num,
206 const ddr2_spd_eeprom_t *spd,
207 dimm_params_t *pdimm,
208 unsigned int dimm_number)
213 if (spd->mem_type != SPD_MEMTYPE_DDR2) {
214 printf("DIMM %u: is not a DDR2 SPD.\n", dimm_number);
218 memset(pdimm, 0, sizeof(dimm_params_t));
222 retval = ddr2_spd_check(spd);
224 printf("DIMM %u: failed checksum\n", dimm_number);
229 * The part name in ASCII in the SPD EEPROM is not null terminated.
230 * Guarantee null termination here by presetting all bytes to 0
231 * and copying the part name in ASCII from the SPD onto it
233 memset(pdimm->mpart, 0, sizeof(pdimm->mpart));
234 memcpy(pdimm->mpart, spd->mpart, sizeof(pdimm->mpart) - 1);
236 /* DIMM organization parameters */
237 pdimm->n_ranks = (spd->mod_ranks & 0x7) + 1;
238 pdimm->rank_density = compute_ranksize(spd->mem_type, spd->rank_dens);
239 pdimm->capacity = pdimm->n_ranks * pdimm->rank_density;
240 pdimm->data_width = spd->dataw;
241 pdimm->primary_sdram_width = spd->primw;
242 pdimm->ec_sdram_width = spd->ecw;
244 /* These are all the types defined by the JEDEC DDR2 SPD 1.3 spec */
245 switch (spd->dimm_type) {
246 case DDR2_SPD_DIMMTYPE_RDIMM:
247 case DDR2_SPD_DIMMTYPE_72B_SO_RDIMM:
248 case DDR2_SPD_DIMMTYPE_MINI_RDIMM:
249 /* Registered/buffered DIMMs */
250 pdimm->registered_dimm = 1;
253 case DDR2_SPD_DIMMTYPE_UDIMM:
254 case DDR2_SPD_DIMMTYPE_SO_DIMM:
255 case DDR2_SPD_DIMMTYPE_MICRO_DIMM:
256 case DDR2_SPD_DIMMTYPE_MINI_UDIMM:
257 /* Unbuffered DIMMs */
258 pdimm->registered_dimm = 0;
261 case DDR2_SPD_DIMMTYPE_72B_SO_CDIMM:
263 printf("unknown dimm_type 0x%02X\n", spd->dimm_type);
267 /* SDRAM device parameters */
268 pdimm->n_row_addr = spd->nrow_addr;
269 pdimm->n_col_addr = spd->ncol_addr;
270 pdimm->n_banks_per_sdram_device = spd->nbanks;
271 pdimm->edc_config = spd->config;
272 pdimm->burst_lengths_bitmask = spd->burstl;
275 * Calculate the Maximum Data Rate based on the Minimum Cycle time.
276 * The SPD clk_cycle field (tCKmin) is measured in tenths of
277 * nanoseconds and represented as BCD.
280 = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle);
281 pdimm->tckmin_x_minus_1_ps
282 = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle2);
283 pdimm->tckmin_x_minus_2_ps
284 = convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle3);
286 pdimm->tckmax_ps = convert_bcd_tenths_to_cycle_time_ps(spd->tckmax);
289 * Compute CAS latencies defined by SPD
290 * The SPD caslat_x should have at least 1 and at most 3 bits set.
292 * If cas_lat after masking is 0, the __ilog2 function returns
293 * 255 into the variable. This behavior is abused once.
295 pdimm->caslat_x = __ilog2(spd->cas_lat);
296 pdimm->caslat_x_minus_1 = __ilog2(spd->cas_lat
297 & ~(1 << pdimm->caslat_x));
298 pdimm->caslat_x_minus_2 = __ilog2(spd->cas_lat
299 & ~(1 << pdimm->caslat_x)
300 & ~(1 << pdimm->caslat_x_minus_1));
302 /* Compute CAS latencies below that defined by SPD */
303 pdimm->caslat_lowest_derated = compute_derated_DDR2_CAS_latency(
304 get_memory_clk_period_ps(ctrl_num));
306 /* Compute timing parameters */
307 pdimm->trcd_ps = spd->trcd * 250;
308 pdimm->trp_ps = spd->trp * 250;
309 pdimm->tras_ps = spd->tras * 1000;
311 pdimm->twr_ps = spd->twr * 250;
312 pdimm->twtr_ps = spd->twtr * 250;
313 pdimm->trfc_ps = compute_trfc_ps_from_spd(spd->trctrfc_ext, spd->trfc);
315 pdimm->trrd_ps = spd->trrd * 250;
316 pdimm->trc_ps = compute_trc_ps_from_spd(spd->trctrfc_ext, spd->trc);
318 pdimm->refresh_rate_ps = determine_refresh_rate_ps(spd->refresh);
320 pdimm->tis_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_setup);
321 pdimm->tih_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_hold);
323 = convert_bcd_hundredths_to_cycle_time_ps(spd->data_setup);
325 = convert_bcd_hundredths_to_cycle_time_ps(spd->data_hold);
327 pdimm->trtp_ps = spd->trtp * 250;
328 pdimm->tdqsq_max_ps = spd->tdqsq * 10;
329 pdimm->tqhs_ps = spd->tqhs * 10;