drivers/ddr/fsl/lc_common_dimm_params.c - filogic/uboot - Gitiles

 /*
  * Copyright 2008-2012 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 <fsl_ddr_sdram.h>

 #include <fsl_ddr.h>

 #if defined(CONFIG_SYS_FSL_DDR3)
 static unsigned int
 compute_cas_latency_ddr3(const dimm_params_t *dimm_params,
 			 common_timing_params_t *outpdimm,
 			 unsigned int number_of_dimms)
 {
 	unsigned int i;
 	unsigned int taamin_ps = 0;
 	unsigned int tckmin_x_ps = 0;
 	unsigned int common_caslat;
 	unsigned int caslat_actual;
 	unsigned int retry = 16;
 	unsigned int tmp;
 	const unsigned int mclk_ps = get_memory_clk_period_ps();

 	/* compute the common CAS latency supported between slots */
 	tmp = dimm_params[0].caslat_x;
 	for (i = 1; i < number_of_dimms; i++) {
 		if (dimm_params[i].n_ranks)
 			tmp &= dimm_params[i].caslat_x;
 	}
 	common_caslat = tmp;

 	/* compute the max tAAmin tCKmin between slots */
 	for (i = 0; i < number_of_dimms; i++) {
 		taamin_ps = max(taamin_ps, dimm_params[i].taa_ps);
 		tckmin_x_ps = max(tckmin_x_ps, dimm_params[i].tckmin_x_ps);
 	}
 	/* validate if the memory clk is in the range of dimms */
 	if (mclk_ps < tckmin_x_ps) {
 		printf("DDR clock (MCLK cycle %u ps) is faster than "
 			"the slowest DIMM(s) (tCKmin %u ps) can support.\n",
 			mclk_ps, tckmin_x_ps);
 	}
 	/* determine the acutal cas latency */
 	caslat_actual = (taamin_ps + mclk_ps - 1) / mclk_ps;
 	/* check if the dimms support the CAS latency */
 	while (!(common_caslat & (1 << caslat_actual)) && retry > 0) {
 		caslat_actual++;
 		retry--;
 	}
 	/* once the caculation of caslat_actual is completed
 	 * we must verify that this CAS latency value does not
 	 * exceed tAAmax, which is 20 ns for all DDR3 speed grades
 	 */
 	if (caslat_actual * mclk_ps > 20000) {
 		printf("The choosen cas latency %d is too large\n",
 			caslat_actual);
 	}
 	outpdimm->lowest_common_SPD_caslat = caslat_actual;

 	return 0;
 }
 #endif

 /*
  * compute_lowest_common_dimm_parameters()
  *
  * Determine the worst-case DIMM timing parameters from the set of DIMMs
  * whose parameters have been computed into the array pointed to
  * by dimm_params.
  */
 unsigned int
 compute_lowest_common_dimm_parameters(const dimm_params_t *dimm_params,
 				      common_timing_params_t *outpdimm,
 				      const unsigned int number_of_dimms)
 {
 	unsigned int i, j;

 	unsigned int tckmin_x_ps = 0;
 	unsigned int tckmax_ps = 0xFFFFFFFF;
 	unsigned int tckmax_max_ps = 0;
 	unsigned int trcd_ps = 0;
 	unsigned int trp_ps = 0;
 	unsigned int tras_ps = 0;
 	unsigned int twr_ps = 0;
 	unsigned int twtr_ps = 0;
 	unsigned int trfc_ps = 0;
 	unsigned int trrd_ps = 0;
 	unsigned int trc_ps = 0;
 	unsigned int refresh_rate_ps = 0;
 	unsigned int extended_op_srt = 1;
 	unsigned int tis_ps = 0;
 	unsigned int tih_ps = 0;
 	unsigned int tds_ps = 0;
 	unsigned int tdh_ps = 0;
 	unsigned int trtp_ps = 0;
 	unsigned int tdqsq_max_ps = 0;
 	unsigned int tqhs_ps = 0;

 	unsigned int temp1, temp2;
 	unsigned int additive_latency = 0;
 #if !defined(CONFIG_SYS_FSL_DDR3)
 	const unsigned int mclk_ps = get_memory_clk_period_ps();
 	unsigned int lowest_good_caslat;
 	unsigned int not_ok;

 	debug("using mclk_ps = %u\n", mclk_ps);
 #endif

 	temp1 = 0;
 	for (i = 0; i < number_of_dimms; i++) {
 		/*
 		 * If there are no ranks on this DIMM,
 		 * it probably doesn't exist, so skip it.
 		 */
 		if (dimm_params[i].n_ranks == 0) {
 			temp1++;
 			continue;
 		}
 		if (dimm_params[i].n_ranks == 4 && i != 0) {
 			printf("Found Quad-rank DIMM in wrong bank, ignored."
 				" Software may not run as expected.\n");
 			temp1++;
 			continue;
 		}

 		/*
 		 * check if quad-rank DIMM is plugged if
 		 * CONFIG_CHIP_SELECT_QUAD_CAPABLE is not defined
 		 * Only the board with proper design is capable
 		 */
 #ifndef CONFIG_FSL_DDR_FIRST_SLOT_QUAD_CAPABLE
 		if (dimm_params[i].n_ranks == 4 && \
 		  CONFIG_CHIP_SELECTS_PER_CTRL/CONFIG_DIMM_SLOTS_PER_CTLR < 4) {
 			printf("Found Quad-rank DIMM, not able to support.");
 			temp1++;
 			continue;
 		}
 #endif
 		/*
 		 * Find minimum tckmax_ps to find fastest slow speed,
 		 * i.e., this is the slowest the whole system can go.
 		 */
 		tckmax_ps = min(tckmax_ps, dimm_params[i].tckmax_ps);

 		/* Either find maximum value to determine slowest
 		 * speed, delay, time, period, etc */
 		tckmin_x_ps = max(tckmin_x_ps, dimm_params[i].tckmin_x_ps);
 		tckmax_max_ps = max(tckmax_max_ps, dimm_params[i].tckmax_ps);
 		trcd_ps = max(trcd_ps, dimm_params[i].trcd_ps);
 		trp_ps = max(trp_ps, dimm_params[i].trp_ps);
 		tras_ps = max(tras_ps, dimm_params[i].tras_ps);
 		twr_ps = max(twr_ps, dimm_params[i].twr_ps);
 		twtr_ps = max(twtr_ps, dimm_params[i].twtr_ps);
 		trfc_ps = max(trfc_ps, dimm_params[i].trfc_ps);
 		trrd_ps = max(trrd_ps, dimm_params[i].trrd_ps);
 		trc_ps = max(trc_ps, dimm_params[i].trc_ps);
 		tis_ps = max(tis_ps, dimm_params[i].tis_ps);
 		tih_ps = max(tih_ps, dimm_params[i].tih_ps);
 		tds_ps = max(tds_ps, dimm_params[i].tds_ps);
 		tdh_ps = max(tdh_ps, dimm_params[i].tdh_ps);
 		trtp_ps = max(trtp_ps, dimm_params[i].trtp_ps);
 		tqhs_ps = max(tqhs_ps, dimm_params[i].tqhs_ps);
 		refresh_rate_ps = max(refresh_rate_ps,
 				      dimm_params[i].refresh_rate_ps);
 		/* extended_op_srt is either 0 or 1, 0 having priority */
 		extended_op_srt = min(extended_op_srt,
 				      dimm_params[i].extended_op_srt);

 		/*
 		 * Find maximum tdqsq_max_ps to find slowest.
 		 *
 		 * FIXME: is finding the slowest value the correct
 		 * strategy for this parameter?
 		 */
 		tdqsq_max_ps = max(tdqsq_max_ps, dimm_params[i].tdqsq_max_ps);
 	}

 	outpdimm->ndimms_present = number_of_dimms - temp1;

 	if (temp1 == number_of_dimms) {
 		debug("no dimms this memory controller\n");
 		return 0;
 	}

 	outpdimm->tckmin_x_ps = tckmin_x_ps;
 	outpdimm->tckmax_ps = tckmax_ps;
 	outpdimm->tckmax_max_ps = tckmax_max_ps;
 	outpdimm->trcd_ps = trcd_ps;
 	outpdimm->trp_ps = trp_ps;
 	outpdimm->tras_ps = tras_ps;
 	outpdimm->twr_ps = twr_ps;
 	outpdimm->twtr_ps = twtr_ps;
 	outpdimm->trfc_ps = trfc_ps;
 	outpdimm->trrd_ps = trrd_ps;
 	outpdimm->trc_ps = trc_ps;
 	outpdimm->refresh_rate_ps = refresh_rate_ps;
 	outpdimm->extended_op_srt = extended_op_srt;
 	outpdimm->tis_ps = tis_ps;
 	outpdimm->tih_ps = tih_ps;
 	outpdimm->tds_ps = tds_ps;
 	outpdimm->tdh_ps = tdh_ps;
 	outpdimm->trtp_ps = trtp_ps;
 	outpdimm->tdqsq_max_ps = tdqsq_max_ps;
 	outpdimm->tqhs_ps = tqhs_ps;

 	/* Determine common burst length for all DIMMs. */
 	temp1 = 0xff;
 	for (i = 0; i < number_of_dimms; i++) {
 		if (dimm_params[i].n_ranks) {
 			temp1 &= dimm_params[i].burst_lengths_bitmask;
 		}
 	}
 	outpdimm->all_dimms_burst_lengths_bitmask = temp1;

 	/* Determine if all DIMMs registered buffered. */
 	temp1 = temp2 = 0;
 	for (i = 0; i < number_of_dimms; i++) {
 		if (dimm_params[i].n_ranks) {
 			if (dimm_params[i].registered_dimm) {
 				temp1 = 1;
 #ifndef CONFIG_SPL_BUILD
 				printf("Detected RDIMM %s\n",
 					dimm_params[i].mpart);
 #endif
 			} else {
 				temp2 = 1;
 #ifndef CONFIG_SPL_BUILD
 				printf("Detected UDIMM %s\n",
 					dimm_params[i].mpart);
 #endif
 			}
 		}
 	}

 	outpdimm->all_dimms_registered = 0;
 	outpdimm->all_dimms_unbuffered = 0;
 	if (temp1 && !temp2) {
 		outpdimm->all_dimms_registered = 1;
 	} else if (!temp1 && temp2) {
 		outpdimm->all_dimms_unbuffered = 1;
 	} else {
 		printf("ERROR:  Mix of registered buffered and unbuffered "
 				"DIMMs detected!\n");
 	}

 	temp1 = 0;
 	if (outpdimm->all_dimms_registered)
 		for (j = 0; j < 16; j++) {
 			outpdimm->rcw[j] = dimm_params[0].rcw[j];
 			for (i = 1; i < number_of_dimms; i++) {
 				if (!dimm_params[i].n_ranks)
 					continue;
 				if (dimm_params[i].rcw[j] != dimm_params[0].rcw[j]) {
 					temp1 = 1;
 					break;
 				}
 			}
 		}

 	if (temp1 != 0)
 		printf("ERROR: Mix different RDIMM detected!\n");

 #if defined(CONFIG_SYS_FSL_DDR3)
 	if (compute_cas_latency_ddr3(dimm_params, outpdimm, number_of_dimms))
 		return 1;
 #else
 	/*
 	 * Compute a CAS latency suitable for all DIMMs
 	 *
 	 * Strategy for SPD-defined latencies: compute only
 	 * CAS latency defined by all DIMMs.
 	 */

 	/*
 	 * Step 1: find CAS latency common to all DIMMs using bitwise
 	 * operation.
 	 */
 	temp1 = 0xFF;
 	for (i = 0; i < number_of_dimms; i++) {
 		if (dimm_params[i].n_ranks) {
 			temp2 = 0;
 			temp2 |= 1 << dimm_params[i].caslat_x;
 			temp2 |= 1 << dimm_params[i].caslat_x_minus_1;
 			temp2 |= 1 << dimm_params[i].caslat_x_minus_2;
 			/*
 			 * FIXME: If there was no entry for X-2 (X-1) in
 			 * the SPD, then caslat_x_minus_2
 			 * (caslat_x_minus_1) contains either 255 or
 			 * 0xFFFFFFFF because that's what the glorious
 			 * __ilog2 function returns for an input of 0.
 			 * On 32-bit PowerPC, left shift counts with bit
 			 * 26 set (that the value of 255 or 0xFFFFFFFF
 			 * will have), cause the destination register to
 			 * be 0.  That is why this works.
 			 */
 			temp1 &= temp2;
 		}
 	}

 	/*
 	 * Step 2: check each common CAS latency against tCK of each
 	 * DIMM's SPD.
 	 */
 	lowest_good_caslat = 0;
 	temp2 = 0;
 	while (temp1) {
 		not_ok = 0;
 		temp2 =  __ilog2(temp1);
 		debug("checking common caslat = %u\n", temp2);

 		/* Check if this CAS latency will work on all DIMMs at tCK. */
 		for (i = 0; i < number_of_dimms; i++) {
 			if (!dimm_params[i].n_ranks) {
 				continue;
 			}
 			if (dimm_params[i].caslat_x == temp2) {
 				if (mclk_ps >= dimm_params[i].tckmin_x_ps) {
 					debug("CL = %u ok on DIMM %u at tCK=%u"
 					    " ps with its tCKmin_X_ps of %u\n",
 					       temp2, i, mclk_ps,
 					       dimm_params[i].tckmin_x_ps);
 					continue;
 				} else {
 					not_ok++;
 				}
 			}

 			if (dimm_params[i].caslat_x_minus_1 == temp2) {
 				unsigned int tckmin_x_minus_1_ps
 					= dimm_params[i].tckmin_x_minus_1_ps;
 				if (mclk_ps >= tckmin_x_minus_1_ps) {
 					debug("CL = %u ok on DIMM %u at "
 						"tCK=%u ps with its "
 						"tckmin_x_minus_1_ps of %u\n",
 					       temp2, i, mclk_ps,
 					       tckmin_x_minus_1_ps);
 					continue;
 				} else {
 					not_ok++;
 				}
 			}

 			if (dimm_params[i].caslat_x_minus_2 == temp2) {
 				unsigned int tckmin_x_minus_2_ps
 					= dimm_params[i].tckmin_x_minus_2_ps;
 				if (mclk_ps >= tckmin_x_minus_2_ps) {
 					debug("CL = %u ok on DIMM %u at "
 						"tCK=%u ps with its "
 						"tckmin_x_minus_2_ps of %u\n",
 					       temp2, i, mclk_ps,
 					       tckmin_x_minus_2_ps);
 					continue;
 				} else {
 					not_ok++;
 				}
 			}
 		}

 		if (!not_ok) {
 			lowest_good_caslat = temp2;
 		}

 		temp1 &= ~(1 << temp2);
 	}

 	debug("lowest common SPD-defined CAS latency = %u\n",
 	       lowest_good_caslat);
 	outpdimm->lowest_common_SPD_caslat = lowest_good_caslat;


 	/*
 	 * Compute a common 'de-rated' CAS latency.
 	 *
 	 * The strategy here is to find the *highest* dereated cas latency
 	 * with the assumption that all of the DIMMs will support a dereated
 	 * CAS latency higher than or equal to their lowest dereated value.
 	 */
 	temp1 = 0;
 	for (i = 0; i < number_of_dimms; i++) {
 		temp1 = max(temp1, dimm_params[i].caslat_lowest_derated);
 	}
 	outpdimm->highest_common_derated_caslat = temp1;
 	debug("highest common dereated CAS latency = %u\n", temp1);
 #endif /* #if defined(CONFIG_SYS_FSL_DDR3) */

 	/* Determine if all DIMMs ECC capable. */
 	temp1 = 1;
 	for (i = 0; i < number_of_dimms; i++) {
 		if (dimm_params[i].n_ranks &&
 			!(dimm_params[i].edc_config & EDC_ECC)) {
 			temp1 = 0;
 			break;
 		}
 	}
 	if (temp1) {
 		debug("all DIMMs ECC capable\n");
 	} else {
 		debug("Warning: not all DIMMs ECC capable, cant enable ECC\n");
 	}
 	outpdimm->all_dimms_ecc_capable = temp1;

 #ifndef CONFIG_SYS_FSL_DDR3
 	/* FIXME: move to somewhere else to validate. */
 	if (mclk_ps > tckmax_max_ps) {
 		printf("Warning: some of the installed DIMMs "
 				"can not operate this slowly.\n");
 		return 1;
 	}
 #endif
 	/*
 	 * Compute additive latency.
 	 *
 	 * For DDR1, additive latency should be 0.
 	 *
 	 * For DDR2, with ODT enabled, use "a value" less than ACTTORW,
 	 *	which comes from Trcd, and also note that:
 	 *	    add_lat + caslat must be >= 4
 	 *
 	 * For DDR3, we use the AL=0
 	 *
 	 * When to use additive latency for DDR2:
 	 *
 	 * I. Because you are using CL=3 and need to do ODT on writes and
 	 *    want functionality.
 	 *    1. Are you going to use ODT? (Does your board not have
 	 *      additional termination circuitry for DQ, DQS, DQS_,
 	 *      DM, RDQS, RDQS_ for x4/x8 configs?)
 	 *    2. If so, is your lowest supported CL going to be 3?
 	 *    3. If so, then you must set AL=1 because
 	 *
 	 *       WL >= 3 for ODT on writes
 	 *       RL = AL + CL
 	 *       WL = RL - 1
 	 *       ->
 	 *       WL = AL + CL - 1
 	 *       AL + CL - 1 >= 3
 	 *       AL + CL >= 4
 	 *  QED
 	 *
 	 *  RL >= 3 for ODT on reads
 	 *  RL = AL + CL
 	 *
 	 *  Since CL aren't usually less than 2, AL=0 is a minimum,
 	 *  so the WL-derived AL should be the  -- FIXME?
 	 *
 	 * II. Because you are using auto-precharge globally and want to
 	 *     use additive latency (posted CAS) to get more bandwidth.
 	 *     1. Are you going to use auto-precharge mode globally?
 	 *
 	 *        Use addtivie latency and compute AL to be 1 cycle less than
 	 *        tRCD, i.e. the READ or WRITE command is in the cycle
 	 *        immediately following the ACTIVATE command..
 	 *
 	 * III. Because you feel like it or want to do some sort of
 	 *      degraded-performance experiment.
 	 *     1.  Do you just want to use additive latency because you feel
 	 *         like it?
 	 *
 	 * Validation:  AL is less than tRCD, and within the other
 	 * read-to-precharge constraints.
 	 */

 	additive_latency = 0;

 #if defined(CONFIG_SYS_FSL_DDR2)
 	if (lowest_good_caslat < 4) {
 		additive_latency = (picos_to_mclk(trcd_ps) > lowest_good_caslat)
 			? picos_to_mclk(trcd_ps) - lowest_good_caslat : 0;
 		if (mclk_to_picos(additive_latency) > trcd_ps) {
 			additive_latency = picos_to_mclk(trcd_ps);
 			debug("setting additive_latency to %u because it was "
 				" greater than tRCD_ps\n", additive_latency);
 		}
 	}

 #elif defined(CONFIG_SYS_FSL_DDR3)
 	/*
 	 * The system will not use the global auto-precharge mode.
 	 * However, it uses the page mode, so we set AL=0
 	 */
 	additive_latency = 0;
 #endif

 	/*
 	 * Validate additive latency
 	 * FIXME: move to somewhere else to validate
 	 *
 	 * AL <= tRCD(min)
 	 */
 	if (mclk_to_picos(additive_latency) > trcd_ps) {
 		printf("Error: invalid additive latency exceeds tRCD(min).\n");
 		return 1;
 	}

 	/*
 	 * RL = CL + AL;  RL >= 3 for ODT_RD_CFG to be enabled
 	 * WL = RL - 1;  WL >= 3 for ODT_WL_CFG to be enabled
 	 * ADD_LAT (the register) must be set to a value less
 	 * than ACTTORW if WL = 1, then AL must be set to 1
 	 * RD_TO_PRE (the register) must be set to a minimum
 	 * tRTP + AL if AL is nonzero
 	 */

 	/*
 	 * Additive latency will be applied only if the memctl option to
 	 * use it.
 	 */
 	outpdimm->additive_latency = additive_latency;

 	debug("tCKmin_ps = %u\n", outpdimm->tckmin_x_ps);
 	debug("trcd_ps   = %u\n", outpdimm->trcd_ps);
 	debug("trp_ps    = %u\n", outpdimm->trp_ps);
 	debug("tras_ps   = %u\n", outpdimm->tras_ps);
 	debug("twr_ps    = %u\n", outpdimm->twr_ps);
 	debug("twtr_ps   = %u\n", outpdimm->twtr_ps);
 	debug("trfc_ps   = %u\n", outpdimm->trfc_ps);
 	debug("trrd_ps   = %u\n", outpdimm->trrd_ps);
 	debug("trc_ps    = %u\n", outpdimm->trc_ps);

 	return 0;
 }
	/*
	* Copyright 2008-2012 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 <fsl_ddr_sdram.h>

	#include <fsl_ddr.h>

	#if defined(CONFIG_SYS_FSL_DDR3)
	static unsigned int
	compute_cas_latency_ddr3(const dimm_params_t *dimm_params,
	common_timing_params_t *outpdimm,
	unsigned int number_of_dimms)
	{
	unsigned int i;
	unsigned int taamin_ps = 0;
	unsigned int tckmin_x_ps = 0;
	unsigned int common_caslat;
	unsigned int caslat_actual;
	unsigned int retry = 16;
	unsigned int tmp;
	const unsigned int mclk_ps = get_memory_clk_period_ps();

	/* compute the common CAS latency supported between slots */
	tmp = dimm_params[0].caslat_x;
	for (i = 1; i < number_of_dimms; i++) {
	if (dimm_params[i].n_ranks)
	tmp &= dimm_params[i].caslat_x;
	}
	common_caslat = tmp;

	/* compute the max tAAmin tCKmin between slots */
	for (i = 0; i < number_of_dimms; i++) {
	taamin_ps = max(taamin_ps, dimm_params[i].taa_ps);
	tckmin_x_ps = max(tckmin_x_ps, dimm_params[i].tckmin_x_ps);
	}
	/* validate if the memory clk is in the range of dimms */
	if (mclk_ps < tckmin_x_ps) {
	printf("DDR clock (MCLK cycle %u ps) is faster than "
	"the slowest DIMM(s) (tCKmin %u ps) can support.\n",
	mclk_ps, tckmin_x_ps);
	}
	/* determine the acutal cas latency */
	caslat_actual = (taamin_ps + mclk_ps - 1) / mclk_ps;
	/* check if the dimms support the CAS latency */
	while (!(common_caslat & (1 << caslat_actual)) && retry > 0) {
	caslat_actual++;
	retry--;
	}
	/* once the caculation of caslat_actual is completed
	* we must verify that this CAS latency value does not
	* exceed tAAmax, which is 20 ns for all DDR3 speed grades
	*/
	if (caslat_actual * mclk_ps > 20000) {
	printf("The choosen cas latency %d is too large\n",
	caslat_actual);
	}
	outpdimm->lowest_common_SPD_caslat = caslat_actual;

	return 0;
	}
	#endif

	/*
	* compute_lowest_common_dimm_parameters()
	*
	* Determine the worst-case DIMM timing parameters from the set of DIMMs
	* whose parameters have been computed into the array pointed to
	* by dimm_params.
	*/
	unsigned int
	compute_lowest_common_dimm_parameters(const dimm_params_t *dimm_params,
	common_timing_params_t *outpdimm,
	const unsigned int number_of_dimms)
	{
	unsigned int i, j;

	unsigned int tckmin_x_ps = 0;
	unsigned int tckmax_ps = 0xFFFFFFFF;
	unsigned int tckmax_max_ps = 0;
	unsigned int trcd_ps = 0;
	unsigned int trp_ps = 0;
	unsigned int tras_ps = 0;
	unsigned int twr_ps = 0;
	unsigned int twtr_ps = 0;
	unsigned int trfc_ps = 0;
	unsigned int trrd_ps = 0;
	unsigned int trc_ps = 0;
	unsigned int refresh_rate_ps = 0;
	unsigned int extended_op_srt = 1;
	unsigned int tis_ps = 0;
	unsigned int tih_ps = 0;
	unsigned int tds_ps = 0;
	unsigned int tdh_ps = 0;
	unsigned int trtp_ps = 0;
	unsigned int tdqsq_max_ps = 0;
	unsigned int tqhs_ps = 0;

	unsigned int temp1, temp2;
	unsigned int additive_latency = 0;
	#if !defined(CONFIG_SYS_FSL_DDR3)
	const unsigned int mclk_ps = get_memory_clk_period_ps();
	unsigned int lowest_good_caslat;
	unsigned int not_ok;

	debug("using mclk_ps = %u\n", mclk_ps);
	#endif

	temp1 = 0;
	for (i = 0; i < number_of_dimms; i++) {
	/*
	* If there are no ranks on this DIMM,
	* it probably doesn't exist, so skip it.
	*/
	if (dimm_params[i].n_ranks == 0) {
	temp1++;
	continue;
	}
	if (dimm_params[i].n_ranks == 4 && i != 0) {
	printf("Found Quad-rank DIMM in wrong bank, ignored."
	" Software may not run as expected.\n");
	temp1++;
	continue;
	}

	/*
	* check if quad-rank DIMM is plugged if
	* CONFIG_CHIP_SELECT_QUAD_CAPABLE is not defined
	* Only the board with proper design is capable
	*/
	#ifndef CONFIG_FSL_DDR_FIRST_SLOT_QUAD_CAPABLE
	if (dimm_params[i].n_ranks == 4 && \
	CONFIG_CHIP_SELECTS_PER_CTRL/CONFIG_DIMM_SLOTS_PER_CTLR < 4) {
	printf("Found Quad-rank DIMM, not able to support.");
	temp1++;
	continue;
	}
	#endif
	/*
	* Find minimum tckmax_ps to find fastest slow speed,
	* i.e., this is the slowest the whole system can go.
	*/
	tckmax_ps = min(tckmax_ps, dimm_params[i].tckmax_ps);

	/* Either find maximum value to determine slowest
	* speed, delay, time, period, etc */
	tckmin_x_ps = max(tckmin_x_ps, dimm_params[i].tckmin_x_ps);
	tckmax_max_ps = max(tckmax_max_ps, dimm_params[i].tckmax_ps);
	trcd_ps = max(trcd_ps, dimm_params[i].trcd_ps);
	trp_ps = max(trp_ps, dimm_params[i].trp_ps);
	tras_ps = max(tras_ps, dimm_params[i].tras_ps);
	twr_ps = max(twr_ps, dimm_params[i].twr_ps);
	twtr_ps = max(twtr_ps, dimm_params[i].twtr_ps);
	trfc_ps = max(trfc_ps, dimm_params[i].trfc_ps);
	trrd_ps = max(trrd_ps, dimm_params[i].trrd_ps);
	trc_ps = max(trc_ps, dimm_params[i].trc_ps);
	tis_ps = max(tis_ps, dimm_params[i].tis_ps);
	tih_ps = max(tih_ps, dimm_params[i].tih_ps);
	tds_ps = max(tds_ps, dimm_params[i].tds_ps);
	tdh_ps = max(tdh_ps, dimm_params[i].tdh_ps);
	trtp_ps = max(trtp_ps, dimm_params[i].trtp_ps);
	tqhs_ps = max(tqhs_ps, dimm_params[i].tqhs_ps);
	refresh_rate_ps = max(refresh_rate_ps,
	dimm_params[i].refresh_rate_ps);
	/* extended_op_srt is either 0 or 1, 0 having priority */
	extended_op_srt = min(extended_op_srt,
	dimm_params[i].extended_op_srt);

	/*
	* Find maximum tdqsq_max_ps to find slowest.
	*
	* FIXME: is finding the slowest value the correct
	* strategy for this parameter?
	*/
	tdqsq_max_ps = max(tdqsq_max_ps, dimm_params[i].tdqsq_max_ps);
	}

	outpdimm->ndimms_present = number_of_dimms - temp1;

	if (temp1 == number_of_dimms) {
	debug("no dimms this memory controller\n");
	return 0;
	}

	outpdimm->tckmin_x_ps = tckmin_x_ps;
	outpdimm->tckmax_ps = tckmax_ps;
	outpdimm->tckmax_max_ps = tckmax_max_ps;
	outpdimm->trcd_ps = trcd_ps;
	outpdimm->trp_ps = trp_ps;
	outpdimm->tras_ps = tras_ps;
	outpdimm->twr_ps = twr_ps;
	outpdimm->twtr_ps = twtr_ps;
	outpdimm->trfc_ps = trfc_ps;
	outpdimm->trrd_ps = trrd_ps;
	outpdimm->trc_ps = trc_ps;
	outpdimm->refresh_rate_ps = refresh_rate_ps;
	outpdimm->extended_op_srt = extended_op_srt;
	outpdimm->tis_ps = tis_ps;
	outpdimm->tih_ps = tih_ps;
	outpdimm->tds_ps = tds_ps;
	outpdimm->tdh_ps = tdh_ps;
	outpdimm->trtp_ps = trtp_ps;
	outpdimm->tdqsq_max_ps = tdqsq_max_ps;
	outpdimm->tqhs_ps = tqhs_ps;

	/* Determine common burst length for all DIMMs. */
	temp1 = 0xff;
	for (i = 0; i < number_of_dimms; i++) {
	if (dimm_params[i].n_ranks) {
	temp1 &= dimm_params[i].burst_lengths_bitmask;
	}
	}
	outpdimm->all_dimms_burst_lengths_bitmask = temp1;

	/* Determine if all DIMMs registered buffered. */
	temp1 = temp2 = 0;
	for (i = 0; i < number_of_dimms; i++) {
	if (dimm_params[i].n_ranks) {
	if (dimm_params[i].registered_dimm) {
	temp1 = 1;
	#ifndef CONFIG_SPL_BUILD
	printf("Detected RDIMM %s\n",
	dimm_params[i].mpart);
	#endif
	} else {
	temp2 = 1;
	#ifndef CONFIG_SPL_BUILD
	printf("Detected UDIMM %s\n",
	dimm_params[i].mpart);
	#endif
	}
	}
	}

	outpdimm->all_dimms_registered = 0;
	outpdimm->all_dimms_unbuffered = 0;
	if (temp1 && !temp2) {
	outpdimm->all_dimms_registered = 1;
	} else if (!temp1 && temp2) {
	outpdimm->all_dimms_unbuffered = 1;
	} else {
	printf("ERROR: Mix of registered buffered and unbuffered "
	"DIMMs detected!\n");
	}

	temp1 = 0;
	if (outpdimm->all_dimms_registered)
	for (j = 0; j < 16; j++) {
	outpdimm->rcw[j] = dimm_params[0].rcw[j];
	for (i = 1; i < number_of_dimms; i++) {
	if (!dimm_params[i].n_ranks)
	continue;
	if (dimm_params[i].rcw[j] != dimm_params[0].rcw[j]) {
	temp1 = 1;
	break;
	}
	}
	}

	if (temp1 != 0)
	printf("ERROR: Mix different RDIMM detected!\n");

	#if defined(CONFIG_SYS_FSL_DDR3)
	if (compute_cas_latency_ddr3(dimm_params, outpdimm, number_of_dimms))
	return 1;
	#else
	/*
	* Compute a CAS latency suitable for all DIMMs
	*
	* Strategy for SPD-defined latencies: compute only
	* CAS latency defined by all DIMMs.
	*/

	/*
	* Step 1: find CAS latency common to all DIMMs using bitwise
	* operation.
	*/
	temp1 = 0xFF;
	for (i = 0; i < number_of_dimms; i++) {
	if (dimm_params[i].n_ranks) {
	temp2 = 0;
	temp2 \|= 1 << dimm_params[i].caslat_x;
	temp2 \|= 1 << dimm_params[i].caslat_x_minus_1;
	temp2 \|= 1 << dimm_params[i].caslat_x_minus_2;
	/*
	* FIXME: If there was no entry for X-2 (X-1) in
	* the SPD, then caslat_x_minus_2
	* (caslat_x_minus_1) contains either 255 or
	* 0xFFFFFFFF because that's what the glorious
	* __ilog2 function returns for an input of 0.
	* On 32-bit PowerPC, left shift counts with bit
	* 26 set (that the value of 255 or 0xFFFFFFFF
	* will have), cause the destination register to
	* be 0. That is why this works.
	*/
	temp1 &= temp2;
	}
	}

	/*
	* Step 2: check each common CAS latency against tCK of each
	* DIMM's SPD.
	*/
	lowest_good_caslat = 0;
	temp2 = 0;
	while (temp1) {
	not_ok = 0;
	temp2 = __ilog2(temp1);
	debug("checking common caslat = %u\n", temp2);

	/* Check if this CAS latency will work on all DIMMs at tCK. */
	for (i = 0; i < number_of_dimms; i++) {
	if (!dimm_params[i].n_ranks) {
	continue;
	}
	if (dimm_params[i].caslat_x == temp2) {
	if (mclk_ps >= dimm_params[i].tckmin_x_ps) {
	debug("CL = %u ok on DIMM %u at tCK=%u"
	" ps with its tCKmin_X_ps of %u\n",
	temp2, i, mclk_ps,
	dimm_params[i].tckmin_x_ps);
	continue;
	} else {
	not_ok++;
	}
	}

	if (dimm_params[i].caslat_x_minus_1 == temp2) {
	unsigned int tckmin_x_minus_1_ps
	= dimm_params[i].tckmin_x_minus_1_ps;
	if (mclk_ps >= tckmin_x_minus_1_ps) {
	debug("CL = %u ok on DIMM %u at "
	"tCK=%u ps with its "
	"tckmin_x_minus_1_ps of %u\n",
	temp2, i, mclk_ps,
	tckmin_x_minus_1_ps);
	continue;
	} else {
	not_ok++;
	}
	}

	if (dimm_params[i].caslat_x_minus_2 == temp2) {
	unsigned int tckmin_x_minus_2_ps
	= dimm_params[i].tckmin_x_minus_2_ps;
	if (mclk_ps >= tckmin_x_minus_2_ps) {
	debug("CL = %u ok on DIMM %u at "
	"tCK=%u ps with its "
	"tckmin_x_minus_2_ps of %u\n",
	temp2, i, mclk_ps,
	tckmin_x_minus_2_ps);
	continue;
	} else {
	not_ok++;
	}
	}
	}

	if (!not_ok) {
	lowest_good_caslat = temp2;
	}

	temp1 &= ~(1 << temp2);
	}

	debug("lowest common SPD-defined CAS latency = %u\n",
	lowest_good_caslat);
	outpdimm->lowest_common_SPD_caslat = lowest_good_caslat;


	/*
	* Compute a common 'de-rated' CAS latency.
	*
	* The strategy here is to find the highest dereated cas latency
	* with the assumption that all of the DIMMs will support a dereated
	* CAS latency higher than or equal to their lowest dereated value.
	*/
	temp1 = 0;
	for (i = 0; i < number_of_dimms; i++) {
	temp1 = max(temp1, dimm_params[i].caslat_lowest_derated);
	}
	outpdimm->highest_common_derated_caslat = temp1;
	debug("highest common dereated CAS latency = %u\n", temp1);
	#endif /* #if defined(CONFIG_SYS_FSL_DDR3) */

	/* Determine if all DIMMs ECC capable. */
	temp1 = 1;
	for (i = 0; i < number_of_dimms; i++) {
	if (dimm_params[i].n_ranks &&
	!(dimm_params[i].edc_config & EDC_ECC)) {
	temp1 = 0;
	break;
	}
	}
	if (temp1) {
	debug("all DIMMs ECC capable\n");
	} else {
	debug("Warning: not all DIMMs ECC capable, cant enable ECC\n");
	}
	outpdimm->all_dimms_ecc_capable = temp1;

	#ifndef CONFIG_SYS_FSL_DDR3
	/* FIXME: move to somewhere else to validate. */
	if (mclk_ps > tckmax_max_ps) {
	printf("Warning: some of the installed DIMMs "
	"can not operate this slowly.\n");
	return 1;
	}
	#endif
	/*
	* Compute additive latency.
	*
	* For DDR1, additive latency should be 0.
	*
	* For DDR2, with ODT enabled, use "a value" less than ACTTORW,
	* which comes from Trcd, and also note that:
	* add_lat + caslat must be >= 4
	*
	* For DDR3, we use the AL=0
	*
	* When to use additive latency for DDR2:
	*
	* I. Because you are using CL=3 and need to do ODT on writes and
	* want functionality.
	* 1. Are you going to use ODT? (Does your board not have
	* additional termination circuitry for DQ, DQS, DQS_,
	* DM, RDQS, RDQS_ for x4/x8 configs?)
	* 2. If so, is your lowest supported CL going to be 3?
	* 3. If so, then you must set AL=1 because
	*
	* WL >= 3 for ODT on writes
	* RL = AL + CL
	* WL = RL - 1
	* ->
	* WL = AL + CL - 1
	* AL + CL - 1 >= 3
	* AL + CL >= 4
	* QED
	*
	* RL >= 3 for ODT on reads
	* RL = AL + CL
	*
	* Since CL aren't usually less than 2, AL=0 is a minimum,
	* so the WL-derived AL should be the -- FIXME?
	*
	* II. Because you are using auto-precharge globally and want to
	* use additive latency (posted CAS) to get more bandwidth.
	* 1. Are you going to use auto-precharge mode globally?
	*
	* Use addtivie latency and compute AL to be 1 cycle less than
	* tRCD, i.e. the READ or WRITE command is in the cycle
	* immediately following the ACTIVATE command..
	*
	* III. Because you feel like it or want to do some sort of
	* degraded-performance experiment.
	* 1. Do you just want to use additive latency because you feel
	* like it?
	*
	* Validation: AL is less than tRCD, and within the other
	* read-to-precharge constraints.
	*/

	additive_latency = 0;

	#if defined(CONFIG_SYS_FSL_DDR2)
	if (lowest_good_caslat < 4) {
	additive_latency = (picos_to_mclk(trcd_ps) > lowest_good_caslat)
	? picos_to_mclk(trcd_ps) - lowest_good_caslat : 0;
	if (mclk_to_picos(additive_latency) > trcd_ps) {
	additive_latency = picos_to_mclk(trcd_ps);
	debug("setting additive_latency to %u because it was "
	" greater than tRCD_ps\n", additive_latency);
	}
	}

	#elif defined(CONFIG_SYS_FSL_DDR3)
	/*
	* The system will not use the global auto-precharge mode.
	* However, it uses the page mode, so we set AL=0
	*/
	additive_latency = 0;
	#endif

	/*
	* Validate additive latency
	* FIXME: move to somewhere else to validate
	*
	* AL <= tRCD(min)
	*/
	if (mclk_to_picos(additive_latency) > trcd_ps) {
	printf("Error: invalid additive latency exceeds tRCD(min).\n");
	return 1;
	}

	/*
	* RL = CL + AL; RL >= 3 for ODT_RD_CFG to be enabled
	* WL = RL - 1; WL >= 3 for ODT_WL_CFG to be enabled
	* ADD_LAT (the register) must be set to a value less
	* than ACTTORW if WL = 1, then AL must be set to 1
	* RD_TO_PRE (the register) must be set to a minimum
	* tRTP + AL if AL is nonzero
	*/

	/*
	* Additive latency will be applied only if the memctl option to
	* use it.
	*/
	outpdimm->additive_latency = additive_latency;

	debug("tCKmin_ps = %u\n", outpdimm->tckmin_x_ps);
	debug("trcd_ps = %u\n", outpdimm->trcd_ps);
	debug("trp_ps = %u\n", outpdimm->trp_ps);
	debug("tras_ps = %u\n", outpdimm->tras_ps);
	debug("twr_ps = %u\n", outpdimm->twr_ps);
	debug("twtr_ps = %u\n", outpdimm->twtr_ps);
	debug("trfc_ps = %u\n", outpdimm->trfc_ps);
	debug("trrd_ps = %u\n", outpdimm->trrd_ps);
	debug("trc_ps = %u\n", outpdimm->trc_ps);

	return 0;
	}