coreboot/default: merge coreboot/haswell

Signed-off-by: Leah Rowe <leah@libreboot.org>

1 files changed, 708 insertions, 0 deletions

diff --git a/config/coreboot/default/patches/0053-haswell-NRI-Add-RcvEn-training.patch b/config/coreboot/default/patches/0053-haswell-NRI-Add-RcvEn-training.patch
new file mode 100644
index 00000000..a9821796
--- /dev/null
+++ b/config/coreboot/default/patches/0053-haswell-NRI-Add-RcvEn-training.patch
@@ -0,0 +1,708 @@
+From 0826d1e9ba50daad13c3d5adccba4b180c82296b Mon Sep 17 00:00:00 2001
+From: Angel Pons <th3fanbus@gmail.com>
+Date: Sun, 8 May 2022 00:05:41 +0200
+Subject: [PATCH 11/17] haswell NRI: Add RcvEn training
+
+Implement the RcvEn (Receive Enable) calibration procedure.
+
+Change-Id: Ifbfa520f3e0486c56d0988ce67af2ddb9cf29888
+Signed-off-by: Angel Pons <th3fanbus@gmail.com>
+---
+ .../intel/haswell/native_raminit/Makefile.mk  |   1 +
+ .../haswell/native_raminit/raminit_main.c     |   1 +
+ .../haswell/native_raminit/raminit_native.h   |  14 +
+ .../haswell/native_raminit/reg_structs.h      |  13 +
+ .../native_raminit/train_receive_enable.c     | 561 ++++++++++++++++++
+ .../intel/haswell/registers/mchbar.h          |   3 +
+ 6 files changed, 593 insertions(+)
+ create mode 100644 src/northbridge/intel/haswell/native_raminit/train_receive_enable.c
+
+diff --git a/src/northbridge/intel/haswell/native_raminit/Makefile.mk b/src/northbridge/intel/haswell/native_raminit/Makefile.mk
+index ebe9e9b762..e2fbfb4211 100644
+--- a/src/northbridge/intel/haswell/native_raminit/Makefile.mk
++++ b/src/northbridge/intel/haswell/native_raminit/Makefile.mk
+@@ -16,3 +16,4 @@ romstage-y += setup_wdb.c
+ romstage-y += spd_bitmunching.c
+ romstage-y += testing_io.c
+ romstage-y += timings_refresh.c
++romstage-y += train_receive_enable.c
+diff --git a/src/northbridge/intel/haswell/native_raminit/raminit_main.c b/src/northbridge/intel/haswell/native_raminit/raminit_main.c
+index 5e4674957d..7d444659c3 100644
+--- a/src/northbridge/intel/haswell/native_raminit/raminit_main.c
++++ b/src/northbridge/intel/haswell/native_raminit/raminit_main.c
+@@ -60,6 +60,7 @@ static const struct task_entry cold_boot[] = {
+ 	{ configure_memory_map,                                   true, "MEMMAP",     },
+ 	{ do_jedec_init,                                          true, "JEDECINIT",  },
+ 	{ pre_training,                                           true, "PRETRAIN",   },
++	{ train_receive_enable,                                   true, "RCVET",      },
+ };
+ 
+ /* Return a generic stepping value to make stepping checks simpler */
+diff --git a/src/northbridge/intel/haswell/native_raminit/raminit_native.h b/src/northbridge/intel/haswell/native_raminit/raminit_native.h
+index 8707257b27..eaaaedad1e 100644
+--- a/src/northbridge/intel/haswell/native_raminit/raminit_native.h
++++ b/src/northbridge/intel/haswell/native_raminit/raminit_native.h
+@@ -43,6 +43,9 @@
+ #define NUM_WDB_CL_MUX_SEEDS	3
+ #define NUM_CADB_MUX_SEEDS	3
+ 
++/* Specified in PI ticks. 64 PI ticks == 1 qclk */
++#define tDQSCK_DRIFT		64
++
+ /* ZQ calibration types */
+ enum {
+ 	ZQ_INIT,	/* DDR3: ZQCL with tZQinit, LPDDR3: ZQ Init  with tZQinit  */
+@@ -189,6 +192,7 @@ enum raminit_status {
+ 	RAMINIT_STATUS_MPLL_INIT_FAILURE,
+ 	RAMINIT_STATUS_POLL_TIMEOUT,
+ 	RAMINIT_STATUS_REUT_ERROR,
++	RAMINIT_STATUS_RCVEN_FAILURE,
+ 	RAMINIT_STATUS_UNSPECIFIED_ERROR, /** TODO: Deprecated in favor of specific values **/
+ };
+ 
+@@ -271,6 +275,10 @@ struct sysinfo {
+ 
+ 	union ddr_data_vref_adjust_reg dimm_vref;
+ 
++	uint8_t io_latency[NUM_CHANNELS][NUM_SLOTRANKS];
++	uint8_t rt_latency[NUM_CHANNELS][NUM_SLOTRANKS];
++	uint32_t rt_io_comp[NUM_CHANNELS];
++
+ 	uint32_t data_offset_train[NUM_CHANNELS][NUM_LANES];
+ 	uint32_t data_offset_comp[NUM_CHANNELS][NUM_LANES];
+ 
+@@ -345,6 +353,11 @@ static inline void clear_data_offset_train_all(struct sysinfo *ctrl)
+ 	memset(ctrl->data_offset_train, 0, sizeof(ctrl->data_offset_train));
+ }
+ 
++static inline uint32_t get_data_train_feedback(const uint8_t channel, const uint8_t byte)
++{
++	return mchbar_read32(DDR_DATA_TRAIN_FEEDBACK(channel, byte));
++}
++
+ /* Number of ticks to wait in units of 69.841279 ns (citation needed) */
+ static inline void tick_delay(const uint32_t delay)
+ {
+@@ -400,6 +413,7 @@ enum raminit_status convert_timings(struct sysinfo *ctrl);
+ enum raminit_status configure_mc(struct sysinfo *ctrl);
+ enum raminit_status configure_memory_map(struct sysinfo *ctrl);
+ enum raminit_status do_jedec_init(struct sysinfo *ctrl);
++enum raminit_status train_receive_enable(struct sysinfo *ctrl);
+ 
+ void configure_timings(struct sysinfo *ctrl);
+ void configure_refresh(struct sysinfo *ctrl);
+diff --git a/src/northbridge/intel/haswell/native_raminit/reg_structs.h b/src/northbridge/intel/haswell/native_raminit/reg_structs.h
+index b943259b91..b099f4bb82 100644
+--- a/src/northbridge/intel/haswell/native_raminit/reg_structs.h
++++ b/src/northbridge/intel/haswell/native_raminit/reg_structs.h
+@@ -297,6 +297,19 @@ union ddr_scram_misc_control_reg {
+ 	uint32_t raw;
+ };
+ 
++union sc_io_latency_reg {
++	struct __packed {
++		uint32_t iolat_rank0     : 4; // Bits  3:0
++		uint32_t iolat_rank1     : 4; // Bits  7:4
++		uint32_t iolat_rank2     : 4; // Bits 11:8
++		uint32_t iolat_rank3     : 4; // Bits 15:12
++		uint32_t rt_iocomp       : 6; // Bits 21:16
++		uint32_t                 : 9; // Bits 30:22
++		uint32_t dis_rt_clk_gate : 1; // Bits 31:31
++	};
++	uint32_t raw;
++};
++
+ union mcscheds_cbit_reg {
+ 	struct __packed {
+ 		uint32_t dis_opp_cas    : 1; // Bits  0:0
+diff --git a/src/northbridge/intel/haswell/native_raminit/train_receive_enable.c b/src/northbridge/intel/haswell/native_raminit/train_receive_enable.c
+new file mode 100644
+index 0000000000..576c6bc21e
+--- /dev/null
++++ b/src/northbridge/intel/haswell/native_raminit/train_receive_enable.c
+@@ -0,0 +1,561 @@
++/* SPDX-License-Identifier: GPL-2.0-or-later */
++
++#include <console/console.h>
++#include <northbridge/intel/haswell/haswell.h>
++#include <types.h>
++
++#include "raminit_native.h"
++#include "ranges.h"
++
++#define RCVEN_PLOT	RAM_DEBUG
++
++static enum raminit_status change_rcven_timing(struct sysinfo *ctrl, const uint8_t channel)
++{
++	int16_t max_rcven = -4096;
++	int16_t min_rcven = 4096;
++	int16_t max_rcven_rank[NUM_SLOTRANKS];
++	int16_t min_rcven_rank[NUM_SLOTRANKS];
++	for (uint8_t rank = 0; rank < NUM_SLOTRANKS; rank++) {
++		max_rcven_rank[rank] = max_rcven;
++		min_rcven_rank[rank] = min_rcven;
++	}
++	for (uint8_t rank = 0; rank < NUM_SLOTRANKS; rank++) {
++		if (!rank_in_ch(ctrl, rank, channel))
++			continue;
++
++		for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++			int16_t new_rcven = ctrl->rcven[channel][rank][byte];
++			new_rcven -= ctrl->io_latency[channel][rank] * 64;
++			if (max_rcven_rank[rank] < new_rcven)
++				max_rcven_rank[rank] = new_rcven;
++
++			if (min_rcven_rank[rank] > new_rcven)
++				min_rcven_rank[rank] = new_rcven;
++		}
++		if (max_rcven < max_rcven_rank[rank])
++			max_rcven = max_rcven_rank[rank];
++
++		if (min_rcven > min_rcven_rank[rank])
++			min_rcven = min_rcven_rank[rank];
++	}
++
++	/*
++	 * Determine how far we are from the ideal center point for RcvEn timing.
++	 * (PiIdeal - AveRcvEn) / 64 is the ideal number of cycles we should have
++	 * for IO latency. command training will reduce this by 64, so plan for
++	 * that now in the ideal value. Round to closest integer.
++	 */
++	const int16_t rre_pi_ideal = 256 + 64;
++	const int16_t pi_reserve = 64;
++	const int16_t rcven_center = (max_rcven + min_rcven) / 2;
++	const int8_t iolat_target = DIV_ROUND_CLOSEST(rre_pi_ideal - rcven_center, 64);
++
++	int8_t io_g_offset = 0;
++	int8_t io_lat[NUM_SLOTRANKS] = { 0 };
++	for (uint8_t rank = 0; rank < NUM_SLOTRANKS; rank++) {
++		if (!rank_in_ch(ctrl, rank, channel))
++			continue;
++
++		io_lat[rank] = iolat_target;
++
++		/* Check for RcvEn underflow/overflow */
++		const int16_t rcven_lower = 64 * io_lat[rank] + min_rcven_rank[rank];
++		if (rcven_lower < pi_reserve)
++			io_lat[rank] += DIV_ROUND_UP(pi_reserve - rcven_lower, 64);
++
++		const int16_t rcven_upper = 64 * io_lat[rank] + max_rcven_rank[rank];
++		if (rcven_upper > 511 - pi_reserve)
++			io_lat[rank] -= DIV_ROUND_UP(rcven_upper - (511 - pi_reserve), 64);
++
++		/* Check for IO latency over/underflow */
++		if (io_lat[rank] - io_g_offset > 14)
++			io_g_offset = io_lat[rank] - 14;
++
++		if (io_lat[rank] - io_g_offset < 1)
++			io_g_offset = io_lat[rank] - 1;
++
++		const int8_t cycle_offset = io_lat[rank] - ctrl->io_latency[channel][rank];
++		for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++			ctrl->rcven[channel][rank][byte] += 64 * cycle_offset;
++			update_rxt(ctrl, channel, rank, byte, RXT_RESTORE, 0);
++		}
++	}
++
++	/* Calculate new IO comp latency */
++	union sc_io_latency_reg sc_io_lat = {
++		.raw = mchbar_read32(SC_IO_LATENCY_ch(channel)),
++	};
++
++	/* Check if we are underflowing or overflowing this field */
++	if (io_g_offset < 0 && sc_io_lat.rt_iocomp < -io_g_offset) {
++		printk(BIOS_ERR, "%s: IO COMP underflow\n", __func__);
++		printk(BIOS_ERR, "io_g_offset: %d\n", io_g_offset);
++		printk(BIOS_ERR, "rt_iocomp: %u\n", sc_io_lat.rt_iocomp);
++		return RAMINIT_STATUS_RCVEN_FAILURE;
++	}
++	if (io_g_offset > 0 && io_g_offset > 0x3f - sc_io_lat.rt_iocomp) {
++		printk(BIOS_ERR, "%s: IO COMP overflow\n", __func__);
++		printk(BIOS_ERR, "io_g_offset: %d\n", io_g_offset);
++		printk(BIOS_ERR, "rt_iocomp: %u\n", sc_io_lat.rt_iocomp);
++		return RAMINIT_STATUS_RCVEN_FAILURE;
++	}
++	sc_io_lat.rt_iocomp += io_g_offset;
++	ctrl->rt_io_comp[channel] = sc_io_lat.rt_iocomp;
++	for (uint8_t rank = 0; rank < NUM_SLOTRANKS; rank++) {
++		if (ctrl->rankmap[channel] & BIT(rank))
++			ctrl->io_latency[channel][rank] = io_lat[rank] - io_g_offset;
++
++		const uint8_t shift = rank * 4;
++		sc_io_lat.raw &= ~(0xf << shift);
++		sc_io_lat.raw |= ctrl->io_latency[channel][rank] << shift;
++	}
++	mchbar_write32(SC_IO_LATENCY_ch(channel), sc_io_lat.raw);
++	return RAMINIT_STATUS_SUCCESS;
++}
++
++#define RL_START (256 + 24)
++#define RL_STOP  (384 + 24)
++#define RL_STEP  8
++
++#define RE_NUM_SAMPLES	6
++
++static enum raminit_status verify_high_region(const int32_t center, const int32_t lwidth)
++{
++	if (center > RL_STOP) {
++		/* Check if center of high was found where it should be */
++		printk(BIOS_ERR, "RcvEn: Center of high (%d) higher than expected\n", center);
++		return RAMINIT_STATUS_RCVEN_FAILURE;
++	}
++	if (lwidth <= 32) {
++		/* Check if width is large enough */
++		printk(BIOS_ERR, "RcvEn: Width of high region (%d) too small\n", lwidth);
++		return RAMINIT_STATUS_RCVEN_FAILURE;
++	}
++	if (lwidth >= 96) {
++		/* Since we're calibrating a phase, a too large region is a problem */
++		printk(BIOS_ERR, "RcvEn: Width of high region (%d) too large\n", lwidth);
++		return RAMINIT_STATUS_RCVEN_FAILURE;
++	}
++	return RAMINIT_STATUS_SUCCESS;
++}
++
++static void program_io_latency(struct sysinfo *ctrl, const uint8_t channel, const uint8_t rank)
++{
++	const uint8_t shift = rank * 4;
++	const uint8_t iolat = ctrl->io_latency[channel][rank];
++	mchbar_clrsetbits32(SC_IO_LATENCY_ch(channel), 0xf << shift, iolat << shift);
++}
++
++static void program_rl_delays(struct sysinfo *ctrl, const uint8_t rank, const uint16_t rl_delay)
++{
++	for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++		if (!rank_in_ch(ctrl, rank, channel))
++			continue;
++
++		for (uint8_t byte = 0; byte < ctrl->lanes; byte++)
++			update_rxt(ctrl, channel, rank, byte, RXT_RCVEN, rl_delay);
++	}
++}
++
++static bool sample_dqs(const uint8_t channel, const uint8_t byte)
++{
++	return (get_data_train_feedback(channel, byte) & 0x1ff) >= BIT(RE_NUM_SAMPLES - 1);
++}
++
++enum raminit_status train_receive_enable(struct sysinfo *ctrl)
++{
++	const struct reut_box reut_addr = {
++		.col = {
++			.start    = 0,
++			.stop     = 1023,
++			.inc_rate = 0,
++			.inc_val  = 1,
++		},
++	};
++	const struct wdb_pat wdb_pattern = {
++		.start_ptr  = 0,
++		.stop_ptr   = 9,
++		.inc_rate   = 32,
++		.dq_pattern = BASIC_VA,
++	};
++
++	const uint16_t bytemask = BIT(ctrl->lanes) - 1;
++	const uint8_t fine_step = 1;
++
++	const uint8_t rt_delta = is_hsw_ult() ? 4 : 2;
++	const uint8_t rt_io_comp = 21 + rt_delta;
++	const uint8_t rt_latency = 16 + rt_delta;
++	setup_io_test(
++		ctrl,
++		ctrl->chanmap,
++		PAT_RD,
++		2,
++		RE_NUM_SAMPLES + 1,
++		&reut_addr,
++		0,
++		&wdb_pattern,
++		0,
++		8);
++
++	for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++		if (!does_ch_exist(ctrl, channel))
++			continue;
++
++		for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++			union ddr_data_control_2_reg data_control_2 = {
++				.raw = ctrl->dq_control_2[channel][byte],
++			};
++			data_control_2.force_rx_on = 1;
++			mchbar_write32(DQ_CONTROL_2(channel, byte), data_control_2.raw);
++		}
++		union ddr_data_control_0_reg data_control_0 = {
++			.raw = ctrl->dq_control_0[channel],
++		};
++		if (ctrl->lpddr) {
++			/**
++			 * W/A for b4618574 - @todo: remove for HSW ULT C0
++			 * Can't have force_odt_on together with leaker, disable LPDDR
++			 * mode during this training step. lpddr_mode is restored
++			 * at the end of this function from the host structure.
++			 */
++			data_control_0.lpddr_mode = 0;
++			mchbar_write32(DDR_DATA_ch_CONTROL_0(channel), data_control_0.raw);
++		}
++		data_control_0.force_odt_on     = 1;
++		data_control_0.rl_training_mode = 1;
++		mchbar_write32(DDR_DATA_ch_CONTROL_0(channel), data_control_0.raw);
++		mchbar_write32(SC_IO_LATENCY_ch(channel), (union sc_io_latency_reg) {
++			.rt_iocomp = rt_io_comp,
++		}.raw);
++	}
++	enum raminit_status status = RAMINIT_STATUS_SUCCESS;
++	for (uint8_t rank = 0; rank < NUM_SLOTRANKS; rank++) {
++		if (!does_rank_exist(ctrl, rank))
++			continue;
++
++		/*
++		 * Set initial roundtrip latency values. Assume -4 QCLK for worst board
++		 * layout. This is calculated as HW_ROUNDT_LAT_DEFAULT_VALUE plus:
++		 *
++		 *   DDR3: Default + (2 * tAA) + 4 QCLK + PI_CLK + N-mode value * 2
++		 * LPDDR3: Default + (2 * tAA) + 4 QCLK + PI_CLK + tDQSCK_max
++		 *
++		 * N-mode is 3 during training mode. Both channels use the same timings.
++		 */
++		/** TODO: differs for LPDDR **/
++		const uint32_t tmp = MAX(ctrl->multiplier, 4) + 5 + 2 * ctrl->tAA;
++		const uint32_t initial_rt_latency = MIN(rt_latency + tmp, 0x3f);
++
++		uint8_t chanmask = 0;
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			chanmask |= select_reut_ranks(ctrl, channel, BIT(rank));
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			ctrl->io_latency[channel][rank] = 0;
++			mchbar_write8(SC_ROUNDT_LAT_ch(channel) + rank, initial_rt_latency);
++			ctrl->rt_latency[channel][rank] = initial_rt_latency;
++		}
++
++		printk(BIOS_DEBUG, "Rank %u\n", rank);
++		printk(BIOS_DEBUG, "Steps 1 and 2: Find middle of high region\n");
++		printk(RCVEN_PLOT, "Byte");
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			printk(RCVEN_PLOT, "\t");
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++)
++				printk(RCVEN_PLOT, "%u ", byte);
++		}
++		printk(RCVEN_PLOT, "\nRcvEn\n");
++		struct phase_train_data region_data[NUM_CHANNELS][NUM_LANES] = { 0 };
++		for (uint16_t rl_delay = RL_START; rl_delay < RL_STOP; rl_delay += RL_STEP) {
++			printk(RCVEN_PLOT, " % 3d", rl_delay);
++			program_rl_delays(ctrl, rank, rl_delay);
++			run_io_test(ctrl, chanmask, BASIC_VA, true);
++			for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++				if (!rank_in_ch(ctrl, rank, channel))
++					continue;
++
++				printk(RCVEN_PLOT, "\t");
++				for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++					const bool high = sample_dqs(channel, byte);
++					printk(RCVEN_PLOT, high ? ". " : "# ");
++					phase_record_pass(
++						&region_data[channel][byte],
++						high,
++						rl_delay,
++						RL_START,
++						RL_STEP);
++				}
++			}
++			printk(RCVEN_PLOT, "\n");
++		}
++		printk(RCVEN_PLOT, "\n");
++		printk(BIOS_DEBUG, "Update RcvEn timing to be in the center of high region\n");
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			printk(BIOS_DEBUG, "C%u.R%u: \tLeft\tRight\tWidth\tCenter\n",
++				channel, rank);
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++				struct phase_train_data *const curr_data =
++						&region_data[channel][byte];
++				phase_append_current_to_initial(curr_data, RL_START, RL_STEP);
++				const int32_t lwidth = range_width(curr_data->largest);
++				const int32_t center = range_center(curr_data->largest);
++				printk(BIOS_DEBUG, "   B%u: \t%d\t%d\t%d\t%d\n",
++					byte,
++					curr_data->largest.start,
++					curr_data->largest.end,
++					lwidth,
++					center);
++
++				status = verify_high_region(center, lwidth);
++				if (status) {
++					printk(BIOS_ERR,
++						"RcvEn problems on channel %u, byte %u\n",
++						channel, byte);
++					goto clean_up;
++				}
++				ctrl->rcven[channel][rank][byte] = center;
++				update_rxt(ctrl, channel, rank, byte, RXT_RESTORE, 0);
++			}
++			printk(BIOS_DEBUG, "\n");
++		}
++
++		printk(BIOS_DEBUG, "Step 3: Quarter preamble - Walk backwards\n");
++		printk(RCVEN_PLOT, "Byte");
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			printk(RCVEN_PLOT, "\t");
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++)
++				printk(RCVEN_PLOT, "%u ", byte);
++		}
++		printk(RCVEN_PLOT, "\nIOLAT\n");
++		bool done = false;
++		while (!done) {
++			run_io_test(ctrl, chanmask, BASIC_VA, true);
++			done = true;
++			for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++				if (!rank_in_ch(ctrl, rank, channel))
++					continue;
++
++				printk(RCVEN_PLOT, "  %2u\t", ctrl->io_latency[channel][rank]);
++				uint16_t highs = 0;
++				for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++					const bool high = sample_dqs(channel, byte);
++					printk(RCVEN_PLOT, high ? "H " : "L ");
++					if (high)
++						highs |= BIT(byte);
++				}
++				if (!highs)
++					continue;
++
++				done = false;
++
++				/* If all bytes sample high, adjust timing globally */
++				if (highs == bytemask && ctrl->io_latency[channel][rank] < 14) {
++					ctrl->io_latency[channel][rank] += 2;
++					ctrl->io_latency[channel][rank] %= 16;
++					program_io_latency(ctrl, channel, rank);
++					continue;
++				}
++
++				/* Otherwise, adjust individual bytes */
++				for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++					if (!(highs & BIT(byte)))
++						continue;
++
++					if (ctrl->rcven[channel][rank][byte] < 128) {
++						printk(BIOS_ERR,
++							"RcvEn underflow: walking backwards\n");
++						printk(BIOS_ERR,
++							"For channel %u, rank %u, byte %u\n",
++							channel, rank, byte);
++						status = RAMINIT_STATUS_RCVEN_FAILURE;
++						goto clean_up;
++					}
++					ctrl->rcven[channel][rank][byte] -= 128;
++					update_rxt(ctrl, channel, rank, byte, RXT_RESTORE, 0);
++				}
++			}
++			printk(RCVEN_PLOT, "\n");
++		}
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			printk(BIOS_DEBUG, "\nC%u:  Preamble\n", channel);
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++				printk(BIOS_DEBUG,
++					" B%u: %u\n", byte, ctrl->rcven[channel][rank][byte]);
++			}
++		}
++		printk(BIOS_DEBUG, "\n");
++
++		printk(BIOS_DEBUG, "Step 4: Add 1 qclk\n");
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++				ctrl->rcven[channel][rank][byte] += 64;
++				update_rxt(ctrl, channel, rank, byte, RXT_RESTORE, 0);
++			}
++		}
++		printk(BIOS_DEBUG, "\n");
++
++		printk(BIOS_DEBUG, "Step 5: Walk forward to find rising edge\n");
++		printk(RCVEN_PLOT, "Byte");
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			printk(RCVEN_PLOT, "\t");
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++)
++				printk(RCVEN_PLOT, "%u ", byte);
++		}
++		printk(RCVEN_PLOT, "\n inc\n");
++		uint16_t ch_result[NUM_CHANNELS] = { 0 };
++		uint8_t inc_preamble[NUM_CHANNELS][NUM_LANES] = { 0 };
++		for (uint8_t inc = 0; inc < 64; inc += fine_step) {
++			printk(RCVEN_PLOT, " %2u\t", inc);
++			run_io_test(ctrl, chanmask, BASIC_VA, true);
++			done = true;
++			for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++				if (!rank_in_ch(ctrl, rank, channel))
++					continue;
++
++				for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++					if (ch_result[channel] & BIT(byte)) {
++						/* Skip bytes that are already done */
++						printk(RCVEN_PLOT, ". ");
++						continue;
++					}
++					const bool pass = sample_dqs(channel, byte);
++					printk(RCVEN_PLOT, pass ? ". " : "# ");
++					if (pass) {
++						ch_result[channel] |= BIT(byte);
++						continue;
++					}
++					ctrl->rcven[channel][rank][byte] += fine_step;
++					update_rxt(ctrl, channel, rank, byte, RXT_RESTORE, 0);
++					inc_preamble[channel][byte] = inc;
++				}
++				printk(RCVEN_PLOT, "\t");
++				if (ch_result[channel] != bytemask)
++					done = false;
++			}
++			printk(RCVEN_PLOT, "\n");
++			if (done)
++				break;
++		}
++		printk(BIOS_DEBUG, "\n");
++		if (!done) {
++			printk(BIOS_ERR, "Error: Preamble edge not found for all bytes\n");
++			printk(BIOS_ERR, "The final RcvEn results are as follows:\n");
++			for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++				if (!rank_in_ch(ctrl, rank, channel))
++					continue;
++
++				printk(BIOS_ERR, "Channel %u Rank %u:  preamble\n",
++					channel, rank);
++				for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++					printk(BIOS_ERR, " Byte %u: %u%s\n", byte,
++						ctrl->rcven[channel][rank][byte],
++						(ch_result[channel] ^ bytemask) & BIT(byte)
++							? ""
++							: " *** Check this byte! ***");
++				}
++			}
++			status = RAMINIT_STATUS_RCVEN_FAILURE;
++			goto clean_up;
++		}
++
++		printk(BIOS_DEBUG, "Step 6: center on preamble and clean up rank\n");
++		for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			printk(BIOS_DEBUG, "C%u:  Preamble increment\n", channel);
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++				/*
++				 * For Traditional, pull in RcvEn by 64. For ULT, take the DQS
++				 * drift into account to the specified guardband: tDQSCK_DRIFT.
++				 */
++				ctrl->rcven[channel][rank][byte] -= tDQSCK_DRIFT;
++				update_rxt(ctrl, channel, rank, byte, RXT_RESTORE, 0);
++				printk(BIOS_DEBUG, " B%u: %u      %u\n", byte,
++					ctrl->rcven[channel][rank][byte],
++					inc_preamble[channel][byte]);
++			}
++			printk(BIOS_DEBUG, "\n");
++		}
++		printk(BIOS_DEBUG, "\n");
++	}
++
++clean_up:
++	for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++		if (!does_ch_exist(ctrl, channel))
++			continue;
++
++		if (ctrl->lpddr) {
++			/**
++			 * W/A for b4618574 - @todo: remove for HSW ULT C0
++			 * Can't have force_odt_on together with leaker, disable LPDDR mode for
++			 * this training step. This write will disable force_odt_on while still
++			 * keeping LPDDR mode disabled. Second write will restore LPDDR mode.
++			 */
++			union ddr_data_control_0_reg data_control_0 = {
++				.raw = ctrl->dq_control_0[channel],
++			};
++			data_control_0.lpddr_mode = 0;
++			mchbar_write32(DDR_DATA_ch_CONTROL_0(channel), data_control_0.raw);
++		}
++		mchbar_write32(DDR_DATA_ch_CONTROL_0(channel), ctrl->dq_control_0[channel]);
++		for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++			mchbar_write32(DQ_CONTROL_2(channel, byte),
++					ctrl->dq_control_2[channel][byte]);
++		}
++	}
++	io_reset();
++	if (status)
++		return status;
++
++	printk(BIOS_DEBUG, "Step 7: Sync IO latency across all ranks\n");
++	for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++		if (!does_ch_exist(ctrl, channel))
++			continue;
++
++		status = change_rcven_timing(ctrl, channel);
++		if (status)
++			return status;
++	}
++	printk(BIOS_DEBUG, "\nFinal Receive Enable and IO latency settings:\n");
++	for (uint8_t channel = 0; channel < NUM_CHANNELS; channel++) {
++		if (!does_ch_exist(ctrl, channel))
++			continue;
++
++		for (uint8_t rank = 0; rank < NUM_SLOTRANKS; rank++) {
++			if (!rank_in_ch(ctrl, rank, channel))
++				continue;
++
++			const union sc_io_latency_reg sc_io_latency = {
++				.raw = mchbar_read32(SC_IO_LATENCY_ch(channel)),
++			};
++			printk(BIOS_DEBUG, "  C%u.R%u: IOLAT = %u  rt_iocomp = %u\n", channel,
++				rank, ctrl->io_latency[channel][rank], sc_io_latency.rt_iocomp);
++			for (uint8_t byte = 0; byte < ctrl->lanes; byte++) {
++				printk(BIOS_DEBUG, "   B%u:   %u\n", byte,
++					ctrl->rcven[channel][rank][byte]);
++			}
++			printk(BIOS_DEBUG, "\n");
++		}
++	}
++	return status;
++}
+diff --git a/src/northbridge/intel/haswell/registers/mchbar.h b/src/northbridge/intel/haswell/registers/mchbar.h
+index a81559bb1e..9172d4f2b0 100644
+--- a/src/northbridge/intel/haswell/registers/mchbar.h
++++ b/src/northbridge/intel/haswell/registers/mchbar.h
+@@ -18,6 +18,8 @@
+ #define RX_TRAIN_ch_r_b(ch, rank, byte)		_DDRIO_C_R_B(0x0000, ch, rank, byte)
+ #define TX_TRAIN_ch_r_b(ch, rank, byte)		_DDRIO_C_R_B(0x0020, ch, rank, byte)
+ 
++#define DDR_DATA_TRAIN_FEEDBACK(ch, byte)	_DDRIO_C_R_B(0x0054, ch, 0, byte)
++
+ #define DQ_CONTROL_2(ch, byte)			_DDRIO_C_R_B(0x0064, ch, 0, byte)
+ #define DQ_CONTROL_0(ch, byte)			_DDRIO_C_R_B(0x0074, ch, 0, byte)
+ 
+@@ -100,6 +102,7 @@
+ #define COMMAND_RATE_LIMIT_ch(ch)		_MCMAIN_C(0x4010, ch)
+ #define TC_BANK_RANK_D_ch(ch)			_MCMAIN_C(0x4014, ch)
+ #define SC_ROUNDT_LAT_ch(ch)			_MCMAIN_C(0x4024, ch)
++#define SC_IO_LATENCY_ch(ch)			_MCMAIN_C(0x4028, ch)
+ 
+ #define REUT_ch_PAT_WDB_CL_MUX_CFG(ch)		_MCMAIN_C(0x4040, ch)
+ 
+-- 
+2.39.2
+