[PATCH 4/8] ppc 8xxx: lowest common dimm parameters

[Renaud Barbier <renaud.barbier@ge.com>]

This file is imported from U-Boot as is.

The code calculates the lowest common DIMM parameters.

Signed-off-by: Renaud Barbier <renaud.barbier@ge.com>
---
 arch/ppc/ddr-8xxx/lc_common_dimm_params.c |  517 +++++++++++++++++++++++++++++
 1 files changed, 517 insertions(+), 0 deletions(-)
 create mode 100644 arch/ppc/ddr-8xxx/lc_common_dimm_params.c

diff --git a/arch/ppc/ddr-8xxx/lc_common_dimm_params.c b/arch/ppc/ddr-8xxx/lc_common_dimm_params.c
new file mode 100644
index 0000000..e958e13
--- /dev/null
+++ b/arch/ppc/ddr-8xxx/lc_common_dimm_params.c
@@ -0,0 +1,517 @@
+/*
+ * 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 <asm/fsl_ddr_sdram.h>
+
+#include "ddr.h"
+
+#if defined(CONFIG_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 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_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);
+
+		/*
+		 * 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->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;
+				printf("Detected RDIMM %s\n",
+					dimm_params[i].mpart);
+			} else {
+				temp2 = 1;
+				printf("Detected UDIMM %s\n",
+					dimm_params[i].mpart);
+			}
+		}
+	}
+
+	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_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_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_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_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_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;
+}
-- 
1.7.1


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