1 /*
2  * Copyright 2008 Freescale Semiconductor, Inc.
3  *
4  * SPDX-License-Identifier:	GPL-2.0
5  */
6 
7 #include <common.h>
8 #include <fsl_ddr_sdram.h>
9 
10 #include <fsl_ddr.h>
11 
12 /*
13  * Calculate the Density of each Physical Rank.
14  * Returned size is in bytes.
15  *
16  * Study these table from Byte 31 of JEDEC SPD Spec.
17  *
18  *		DDR I	DDR II
19  *	Bit	Size	Size
20  *	---	-----	------
21  *	7 high	512MB	512MB
22  *	6	256MB	256MB
23  *	5	128MB	128MB
24  *	4	 64MB	 16GB
25  *	3	 32MB	  8GB
26  *	2	 16MB	  4GB
27  *	1	  2GB	  2GB
28  *	0 low	  1GB	  1GB
29  *
30  * Reorder Table to be linear by stripping the bottom
31  * 2 or 5 bits off and shifting them up to the top.
32  */
33 
34 static unsigned long long
35 compute_ranksize(unsigned int mem_type, unsigned char row_dens)
36 {
37 	unsigned long long bsize;
38 
39 	/* Bottom 2 bits up to the top. */
40 	bsize = ((row_dens >> 2) | ((row_dens & 3) << 6));
41 	bsize <<= 24ULL;
42 	debug("DDR: DDR I rank density = 0x%16llx\n", bsize);
43 
44 	return bsize;
45 }
46 
47 /*
48  * Convert a two-nibble BCD value into a cycle time.
49  * While the spec calls for nano-seconds, picos are returned.
50  *
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.)
56  */
57 static unsigned int
58 convert_bcd_tenths_to_cycle_time_ps(unsigned int spd_val)
59 {
60 	/* Table look up the lower nibble, allow DDR I & II. */
61 	unsigned int tenths_ps[16] = {
62 		0,
63 		100,
64 		200,
65 		300,
66 		400,
67 		500,
68 		600,
69 		700,
70 		800,
71 		900,
72 		250,	/* This and the next 3 entries valid ... */
73 		330,	/* ...  only for tCK calculations. */
74 		660,
75 		750,
76 		0,	/* undefined */
77 		0	/* undefined */
78 	};
79 
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];
83 
84 	return ps;
85 }
86 
87 static unsigned int
88 convert_bcd_hundredths_to_cycle_time_ps(unsigned int spd_val)
89 {
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;
93 
94 	return ps;
95 }
96 
97 static unsigned int byte40_table_ps[8] = {
98 	0,
99 	250,
100 	330,
101 	500,
102 	660,
103 	750,
104 	0,	/* supposed to be RFC, but not sure what that means */
105 	0	/* Undefined */
106 };
107 
108 static unsigned int
109 compute_trfc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trfc)
110 {
111 	return ((trctrfc_ext & 0x1) * 256 + trfc) * 1000
112 		+ byte40_table_ps[(trctrfc_ext >> 1) & 0x7];
113 }
114 
115 static unsigned int
116 compute_trc_ps_from_spd(unsigned char trctrfc_ext, unsigned char trc)
117 {
118 	return trc * 1000 + byte40_table_ps[(trctrfc_ext >> 4) & 0x7];
119 }
120 
121 /*
122  * tCKmax from DDR I SPD Byte 43
123  *
124  * Bits 7:2 == whole ns
125  * Bits 1:0 == quarter ns
126  *    00    == 0.00 ns
127  *    01    == 0.25 ns
128  *    10    == 0.50 ns
129  *    11    == 0.75 ns
130  *
131  * Returns picoseconds.
132  */
133 static unsigned int
134 compute_tckmax_from_spd_ps(unsigned int byte43)
135 {
136 	return (byte43 >> 2) * 1000 + (byte43 & 0x3) * 250;
137 }
138 
139 /*
140  * Determine Refresh Rate.  Ignore self refresh bit on DDR I.
141  * Table from SPD Spec, Byte 12, converted to picoseconds and
142  * filled in with "default" normal values.
143  */
144 static unsigned int
145 determine_refresh_rate_ps(const unsigned int spd_refresh)
146 {
147 	unsigned int refresh_time_ps[8] = {
148 		15625000,	/* 0 Normal    1.00x */
149 		3900000,	/* 1 Reduced    .25x */
150 		7800000,	/* 2 Extended   .50x */
151 		31300000,	/* 3 Extended  2.00x */
152 		62500000,	/* 4 Extended  4.00x */
153 		125000000,	/* 5 Extended  8.00x */
154 		15625000,	/* 6 Normal    1.00x  filler */
155 		15625000,	/* 7 Normal    1.00x  filler */
156 	};
157 
158 	return refresh_time_ps[spd_refresh & 0x7];
159 }
160 
161 /*
162  * The purpose of this function is to compute a suitable
163  * CAS latency given the DRAM clock period.  The SPD only
164  * defines at most 3 CAS latencies.  Typically the slower in
165  * frequency the DIMM runs at, the shorter its CAS latency can be.
166  * If the DIMM is operating at a sufficiently low frequency,
167  * it may be able to run at a CAS latency shorter than the
168  * shortest SPD-defined CAS latency.
169  *
170  * If a CAS latency is not found, 0 is returned.
171  *
172  * Do this by finding in the standard speed bin table the longest
173  * tCKmin that doesn't exceed the value of mclk_ps (tCK).
174  *
175  * An assumption made is that the SDRAM device allows the
176  * CL to be programmed for a value that is lower than those
177  * advertised by the SPD.  This is not always the case,
178  * as those modes not defined in the SPD are optional.
179  *
180  * CAS latency de-rating based upon values JEDEC Standard No. 79-E
181  * Table 11.
182  *
183  * ordinal 2, ddr1_speed_bins[1] contains tCK for CL=2
184  */
185 				  /*   CL2.0 CL2.5 CL3.0  */
186 unsigned short ddr1_speed_bins[] = {0, 7500, 6000, 5000 };
187 
188 unsigned int
189 compute_derated_DDR1_CAS_latency(unsigned int mclk_ps)
190 {
191 	const unsigned int num_speed_bins = ARRAY_SIZE(ddr1_speed_bins);
192 	unsigned int lowest_tCKmin_found = 0;
193 	unsigned int lowest_tCKmin_CL = 0;
194 	unsigned int i;
195 
196 	debug("mclk_ps = %u\n", mclk_ps);
197 
198 	for (i = 0; i < num_speed_bins; i++) {
199 		unsigned int x = ddr1_speed_bins[i];
200 		debug("i=%u, x = %u, lowest_tCKmin_found = %u\n",
201 		      i, x, lowest_tCKmin_found);
202 		if (x && lowest_tCKmin_found <= x && x <= mclk_ps) {
203 			lowest_tCKmin_found = x;
204 			lowest_tCKmin_CL = i + 1;
205 		}
206 	}
207 
208 	debug("lowest_tCKmin_CL = %u\n", lowest_tCKmin_CL);
209 
210 	return lowest_tCKmin_CL;
211 }
212 
213 /*
214  * ddr_compute_dimm_parameters for DDR1 SPD
215  *
216  * Compute DIMM parameters based upon the SPD information in spd.
217  * Writes the results to the dimm_params_t structure pointed by pdimm.
218  *
219  * FIXME: use #define for the retvals
220  */
221 unsigned int ddr_compute_dimm_parameters(const unsigned int ctrl_num,
222 					 const ddr1_spd_eeprom_t *spd,
223 					 dimm_params_t *pdimm,
224 					 unsigned int dimm_number)
225 {
226 	unsigned int retval;
227 
228 	if (spd->mem_type) {
229 		if (spd->mem_type != SPD_MEMTYPE_DDR) {
230 			printf("DIMM %u: is not a DDR1 SPD.\n", dimm_number);
231 			return 1;
232 		}
233 	} else {
234 		memset(pdimm, 0, sizeof(dimm_params_t));
235 		return 1;
236 	}
237 
238 	retval = ddr1_spd_check(spd);
239 	if (retval) {
240 		printf("DIMM %u: failed checksum\n", dimm_number);
241 		return 2;
242 	}
243 
244 	/*
245 	 * The part name in ASCII in the SPD EEPROM is not null terminated.
246 	 * Guarantee null termination here by presetting all bytes to 0
247 	 * and copying the part name in ASCII from the SPD onto it
248 	 */
249 	memset(pdimm->mpart, 0, sizeof(pdimm->mpart));
250 	memcpy(pdimm->mpart, spd->mpart, sizeof(pdimm->mpart) - 1);
251 
252 	/* DIMM organization parameters */
253 	pdimm->n_ranks = spd->nrows;
254 	pdimm->rank_density = compute_ranksize(spd->mem_type, spd->bank_dens);
255 	pdimm->capacity = pdimm->n_ranks * pdimm->rank_density;
256 	pdimm->data_width = spd->dataw_lsb;
257 	pdimm->primary_sdram_width = spd->primw;
258 	pdimm->ec_sdram_width = spd->ecw;
259 
260 	/*
261 	 * FIXME: Need to determine registered_dimm status.
262 	 *     1 == register buffered
263 	 *     0 == unbuffered
264 	 */
265 	pdimm->registered_dimm = 0;	/* unbuffered */
266 
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;
273 	pdimm->row_density = spd->bank_dens;
274 
275 	/*
276 	 * Calculate the Maximum Data Rate based on the Minimum Cycle time.
277 	 * The SPD clk_cycle field (tCKmin) is measured in tenths of
278 	 * nanoseconds and represented as BCD.
279 	 */
280 	pdimm->tckmin_x_ps
281 		= convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle);
282 	pdimm->tckmin_x_minus_1_ps
283 		= convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle2);
284 	pdimm->tckmin_x_minus_2_ps
285 		= convert_bcd_tenths_to_cycle_time_ps(spd->clk_cycle3);
286 
287 	pdimm->tckmax_ps = compute_tckmax_from_spd_ps(spd->tckmax);
288 
289 	/*
290 	 * Compute CAS latencies defined by SPD
291 	 * The SPD caslat_x should have at least 1 and at most 3 bits set.
292 	 *
293 	 * If cas_lat after masking is 0, the __ilog2 function returns
294 	 * 255 into the variable.   This behavior is abused once.
295 	 */
296 	pdimm->caslat_x  = __ilog2(spd->cas_lat);
297 	pdimm->caslat_x_minus_1 = __ilog2(spd->cas_lat
298 					  & ~(1 << pdimm->caslat_x));
299 	pdimm->caslat_x_minus_2 = __ilog2(spd->cas_lat
300 					  & ~(1 << pdimm->caslat_x)
301 					  & ~(1 << pdimm->caslat_x_minus_1));
302 
303 	/* Compute CAS latencies below that defined by SPD */
304 	pdimm->caslat_lowest_derated = compute_derated_DDR1_CAS_latency(
305 					get_memory_clk_period_ps(ctrl_num));
306 
307 	/* Compute timing parameters */
308 	pdimm->trcd_ps = spd->trcd * 250;
309 	pdimm->trp_ps = spd->trp * 250;
310 	pdimm->tras_ps = spd->tras * 1000;
311 
312 	pdimm->twr_ps = mclk_to_picos(ctrl_num, 3);
313 	pdimm->twtr_ps = mclk_to_picos(ctrl_num, 1);
314 	pdimm->trfc_ps = compute_trfc_ps_from_spd(0, spd->trfc);
315 
316 	pdimm->trrd_ps = spd->trrd * 250;
317 	pdimm->trc_ps = compute_trc_ps_from_spd(0, spd->trc);
318 
319 	pdimm->refresh_rate_ps = determine_refresh_rate_ps(spd->refresh);
320 
321 	pdimm->tis_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_setup);
322 	pdimm->tih_ps = convert_bcd_hundredths_to_cycle_time_ps(spd->ca_hold);
323 	pdimm->tds_ps
324 		= convert_bcd_hundredths_to_cycle_time_ps(spd->data_setup);
325 	pdimm->tdh_ps
326 		= convert_bcd_hundredths_to_cycle_time_ps(spd->data_hold);
327 
328 	pdimm->trtp_ps = mclk_to_picos(ctrl_num, 2);	/* By the book. */
329 	pdimm->tdqsq_max_ps = spd->tdqsq * 10;
330 	pdimm->tqhs_ps = spd->tqhs * 10;
331 
332 	return 0;
333 }
334