FSL DDR: Add DDR2 DIMM paramter support

Compute DIMM parameters based upon the SPD information.

Signed-off-by: James Yang <James.Yang@freescale.com>
Signed-off-by: Jon Loeliger <jdl@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 339 insertions, 0 deletions

diff --git a/cpu/mpc8xxx/ddr/ddr2_dimm_params.c b/cpu/mpc8xxx/ddr/ddr2_dimm_params.c
new file mode 100644
index 0000000..06a8eb6
--- /dev/null
+++ b/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 phys_size_t
+compute_ranksize(unsigned int mem_type, unsigned char row_dens)
+{
+	phys_size_t 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;
+}