ddr: vybrid: Provide code to perform on-boot calibration

This patch provides the code to calibrate the DDR's
DQS to DQ signals (RDLVL).

It is based on:
VFxxx Controller Reference Manual, Rev. 0, 10/2016, page 1600
10.1.6.16.4.1 "Software Read Leveling in MC Evaluation Mode"

and NXP's community thread:
"Vybrid: About DDR leveling feature on DDRMC."
https://community.nxp.com/thread/395323Signed-off-by: NLukasz Majewski <lukma@denx.de>

arch/arm/mach-imx/Kconfig

@@ -78,3 +78,15 @@ config NXP_BOARD_REVISION
 	  NXP boards based on i.MX6/7 contain the board revision information
 	  stored in the fuses. Select this option if you want to be able to
 	  retrieve the board revision information.
+
+config DDRMC_VF610_CALIBRATION
+	bool "Enable DDRMC (DDR3) on-chip calibration"
+	depends on ARCH_VF610
+	help
+	  Vybrid (vf610) SoC provides some on-chip facility to tune the DDR3
+	  memory parameters. Select this option if you want to calculate them
+	  at boot time.
+	  NOTE:
+	  NXP does NOT recommend to perform this calibration at each boot. One
+	  shall perform it on a new PCB and then use those values to program
+	  the ddrmc_cr_setting on relevant board file.

arch/arm/mach-imx/Makefile

@@ -53,6 +53,7 @@ obj-$(CONFIG_SECURE_BOOT) += hab.o
 endif
 ifeq ($(SOC),$(filter $(SOC),vf610))
 obj-y += ddrmc-vf610.o
+obj-$(CONFIG_DDRMC_VF610_CALIBRATION) += ddrmc-vf610-calibration.o
 endif
 ifneq ($(CONFIG_SPL_BUILD),y)
 obj-$(CONFIG_CMD_BMODE) += cmd_bmode.o

arch/arm/mach-imx/ddrmc-vf610-calibration.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ddrmc DDR3 calibration code for NXP's VF610
+ *
+ * Copyright (C) 2018 DENX Software Engineering
+ * Lukasz Majewski, DENX Software Engineering, lukma@denx.de
+ *
+ */
+/* #define DEBUG */
+#include <common.h>
+#include <asm/io.h>
+#include <asm/arch/imx-regs.h>
+#include <linux/bitmap.h>
+
+#include "ddrmc-vf610-calibration.h"
+
+/*
+ * Documents:
+ *
+ * [1] "Vybrid: About DDR leveling feature on DDRMC."
+ * https://community.nxp.com/thread/395323
+ *
+ * [2] VFxxx Controller Reference Manual, Rev. 0, 10/2016
+ *
+ *
+ * NOTE
+ * ====
+ *
+ * NXP recommends setting 'fixed' parameters instead of performing the
+ * training at each boot.
+ *
+ * Use those functions to determine those values on new HW, read the
+ * calculated value from registers and add them to the board specific
+ * struct ddrmc_cr_setting.
+ *
+ * SW leveling supported operations - CR93[SW_LVL_MODE]:
+ *
+ * - 0x0 (b'00) - No leveling
+ *
+ * - 0x1 (b'01) - WRLVL_DL_X - It is not recommended to perform this tuning
+ *                             on HW designs utilizing non-flyback topology
+ *                             (Single DDR3 with x16).
+ *                             Instead the WRLVL_DL_0/1 fields shall be set
+ *                             based on trace length differences from their
+ *                             layout.
+ *                             Mismatches up to 25% or tCK (clock period) are
+ *                             allowed, so the value in the filed doesn’t have
+ *                             to be very accurate.
+ *
+ * - 0x2 (b'10) - RDLVL_DL_0/1 - refers to adjusting the DQS strobe in relation
+ *                             to the DQ signals so that the strobe edge is
+ *                             centered in the window of valid read data.
+ *
+ * - 0x3 (b'11) - RDLVL_GTDL_0/1 - refers to the delay the PHY uses to un-gate
+ *                             the Read DQS strobe pad from the time that the
+ *                             PHY enables the pad to input the strobe signal.
+ *
+ */
+static int ddr_cal_get_first_edge_index(unsigned long *bmap, enum edge e,
+					int samples, int start, int max)
+{
+	int i, ret = -1;
+
+	/*
+	 * We look only for the first value (and filter out
+	 * some wrong data)
+	 */
+	switch (e) {
+	case RISING_EDGE:
+		for (i = start; i <= max - samples; i++) {
+			if (test_bit(i, bmap)) {
+				if (!test_bit(i - 1, bmap) &&
+				    test_bit(i + 1, bmap) &&
+				    test_bit(i + 2, bmap) &&
+				    test_bit(i + 3, bmap)) {
+					return i;
+				}
+			}
+		}
+		break;
+	case FALLING_EDGE:
+		for (i = start; i <= max - samples; i++) {
+			if (!test_bit(i, bmap)) {
+				if (test_bit(i - 1, bmap) &&
+				    test_bit(i - 2, bmap) &&
+				    test_bit(i - 3, bmap)) {
+					return i;
+				}
+			}
+		}
+	}
+
+	return ret;
+}
+
+static void bitmap_print(unsigned long *bmap, int max)
+{
+	int i;
+
+	debug("BITMAP [0x%p]:\n", bmap);
+	for (i = 0; i <= max; i++) {
+		debug("%d ", test_bit(i, bmap) ? 1 : 0);
+		if (i && (i % 32) == (32 - 1))
+			debug("\n");
+	}
+	debug("\n");
+}
+
+#define sw_leveling_op_done \
+	while (!(readl(&ddrmr->cr[94]) & DDRMC_CR94_SWLVL_OP_DONE))
+
+#define sw_leveling_load_value \
+	do { clrsetbits_le32(&ddrmr->cr[93], DDRMC_CR93_SWLVL_LOAD, \
+			     DDRMC_CR93_SWLVL_LOAD); } while (0)
+
+#define sw_leveling_start \
+	do { clrsetbits_le32(&ddrmr->cr[93], DDRMC_CR93_SWLVL_START, \
+			     DDRMC_CR93_SWLVL_START); } while (0)
+
+#define sw_leveling_exit \
+	do { clrsetbits_le32(&ddrmr->cr[94], DDRMC_CR94_SWLVL_EXIT, \
+			     DDRMC_CR94_SWLVL_EXIT); } while (0)
+
+/*
+ * RDLVL_DL calibration:
+ *
+ * NXP is _NOT_ recommending performing the leveling at each
+ * boot. Instead - one shall run this procedure on new boards
+ * and then use hardcoded values.
+ *
+ */
+static int ddrmc_cal_dqs_to_dq(struct ddrmr_regs *ddrmr)
+{
+	DECLARE_BITMAP(rdlvl_rsp, DDRMC_DQS_DQ_MAX_DELAY + 1);
+	int rdlvl_dl_0_min = -1, rdlvl_dl_0_max = -1;
+	int rdlvl_dl_1_min = -1, rdlvl_dl_1_max = -1;
+	int rdlvl_dl_0, rdlvl_dl_1;
+	u8 swlvl_rsp;
+	u32 tmp;
+	int i;
+
+	/* Read defaults */
+	u16 rdlvl_dl_0_def =
+		(readl(&ddrmr->cr[105]) >> DDRMC_CR105_RDLVL_DL_0_OFF) & 0xFFFF;
+	u16 rdlvl_dl_1_def = readl(&ddrmr->cr[110]) & 0xFFFF;
+
+	debug("\nRDLVL: ======================\n");
+	debug("RDLVL: DQS to DQ (RDLVL)\n");
+
+	debug("RDLVL: RDLVL_DL_0_DFL:\t 0x%x\n", rdlvl_dl_0_def);
+	debug("RDLVL: RDLVL_DL_1_DFL:\t 0x%x\n", rdlvl_dl_1_def);
+
+	/*
+	 * Set/Read setup for calibration
+	 *
+	 * Values necessary for leveling from Vybrid RM [2] - page 1600
+	 */
+	writel(0x40703030, &ddrmr->cr[144]);
+	writel(0x40, &ddrmr->cr[145]);
+	writel(0x40, &ddrmr->cr[146]);
+
+	tmp = readl(&ddrmr->cr[144]);
+	debug("RDLVL: PHY_RDLVL_RES:\t 0x%x\n", (tmp >> 24) & 0xFF);// set 0x40
+	debug("RDLVL: PHY_RDLV_LOAD:\t 0x%x\n", (tmp >> 16) & 0xFF);// set 0x70
+	debug("RDLVL: PHY_RDLV_DLL:\t 0x%x\n", (tmp >> 8) & 0xFF); // set 0x30
+	debug("RDLVL: PHY_RDLV_EN:\t 0x%x\n", tmp & 0xFF); //set 0x30
+
+	tmp = readl(&ddrmr->cr[145]);
+	debug("RDLVL: PHY_RDLV_RR:\t 0x%x\n", tmp & 0x3FF); //set 0x40
+
+	tmp = readl(&ddrmr->cr[146]);
+	debug("RDLVL: PHY_RDLV_RESP:\t 0x%x\n", tmp); //set 0x40
+
+	/*
+	 * Program/read the leveling edge RDLVL_EDGE = 0
+	 *
+	 * 0x00 is the correct output on SWLVL_RSP_X
+	 * If by any chance 1s are visible -> wrong number read
+	 */
+	clrbits_le32(&ddrmr->cr[101], DDRMC_CR101_PHY_RDLVL_EDGE);
+
+	tmp = readl(&ddrmr->cr[101]);
+	debug("RDLVL: PHY_RDLVL_EDGE:\t 0x%x\n",
+	      (tmp >> DDRMC_CR101_PHY_RDLVL_EDGE_OFF) & 0x1); //set 0
+
+	/* Program Leveling mode - CR93[SW_LVL_MODE] to ’b10 */
+	clrsetbits_le32(&ddrmr->cr[93], DDRMC_CR93_SW_LVL_MODE(0x3),
+			DDRMC_CR93_SW_LVL_MODE(0x2));
+	tmp = readl(&ddrmr->cr[93]);
+	debug("RDLVL: SW_LVL_MODE:\t 0x%x\n",
+	      (tmp >> DDRMC_CR93_SW_LVL_MODE_OFF) & 0x3);
+
+	/* Start procedure - CR93[SWLVL_START] to ’b1 */
+	sw_leveling_start;
+
+	/* Poll CR94[SWLVL_OP_DONE] */
+	sw_leveling_op_done;
+
+	/*
+	 * Program delays for RDLVL_DL_0
+	 *
+	 * The procedure is to increase the delay values from 0 to 0xFF
+	 * and read the response from the DDRMC
+	 */
+	debug("\nRDLVL: ---> RDLVL_DL_0\n");
+	bitmap_zero(rdlvl_rsp, DDRMC_DQS_DQ_MAX_DELAY + 1);
+
+	for (i = 0; i <= DDRMC_DQS_DQ_MAX_DELAY; i++) {
+		clrsetbits_le32(&ddrmr->cr[105],
+				0xFFFF << DDRMC_CR105_RDLVL_DL_0_OFF,
+				i << DDRMC_CR105_RDLVL_DL_0_OFF);
+
+		/* Load values CR93[SWLVL_LOAD] to ’b1 */
+		sw_leveling_load_value;
+
+		/* Poll CR94[SWLVL_OP_DONE] */
+		sw_leveling_op_done;
+
+		/*
+		 * Read Responses - SWLVL_RESP_0
+		 *
+		 * The 0x00 (correct response when PHY_RDLVL_EDGE = 0)
+		 * -> 1 in the bit vector
+		 */
+		swlvl_rsp = (readl(&ddrmr->cr[94]) >>
+			     DDRMC_CR94_SWLVL_RESP_0_OFF) & 0xF;
+		if (swlvl_rsp == 0)
+			generic_set_bit(i, rdlvl_rsp);
+	}
+
+	bitmap_print(rdlvl_rsp, DDRMC_DQS_DQ_MAX_DELAY);
+
+	/*
+	 * First test for rising edge 0x0 -> 0x1 in bitmap
+	 */
+	rdlvl_dl_0_min = ddr_cal_get_first_edge_index(rdlvl_rsp, RISING_EDGE,
+						      N_SAMPLES, N_SAMPLES,
+						      DDRMC_DQS_DQ_MAX_DELAY);
+
+	/*
+	 * Secondly test for falling edge 0x1 -> 0x0 in bitmap
+	 */
+	rdlvl_dl_0_max = ddr_cal_get_first_edge_index(rdlvl_rsp, FALLING_EDGE,
+						      N_SAMPLES, rdlvl_dl_0_min,
+						      DDRMC_DQS_DQ_MAX_DELAY);
+
+	debug("RDLVL: DL_0 min: %d [0x%x] DL_0 max: %d [0x%x]\n",
+	      rdlvl_dl_0_min, rdlvl_dl_0_min, rdlvl_dl_0_max, rdlvl_dl_0_max);
+	rdlvl_dl_0 = (rdlvl_dl_0_max - rdlvl_dl_0_min) / 2;
+
+	if (rdlvl_dl_0_max == -1 || rdlvl_dl_0_min == -1 || rdlvl_dl_0 <= 0) {
+		debug("RDLVL: The DQS to DQ delay cannot be found!\n");
+		debug("RDLVL: Using default - slice 0: %d!\n", rdlvl_dl_0_def);
+		rdlvl_dl_0 = rdlvl_dl_0_def;
+	}
+
+	debug("\nRDLVL: ---> RDLVL_DL_1\n");
+	bitmap_zero(rdlvl_rsp, DDRMC_DQS_DQ_MAX_DELAY + 1);
+
+	for (i = 0; i <= DDRMC_DQS_DQ_MAX_DELAY; i++) {
+		clrsetbits_le32(&ddrmr->cr[110],
+				0xFFFF << DDRMC_CR110_RDLVL_DL_1_OFF,
+				i << DDRMC_CR110_RDLVL_DL_1_OFF);
+
+		/* Load values CR93[SWLVL_LOAD] to ’b1 */
+		sw_leveling_load_value;
+
+		/* Poll CR94[SWLVL_OP_DONE] */
+		sw_leveling_op_done;
+
+		/*
+		 * Read Responses - SWLVL_RESP_1
+		 *
+		 * The 0x00 (correct response when PHY_RDLVL_EDGE = 0)
+		 * -> 1 in the bit vector
+		 */
+		swlvl_rsp = (readl(&ddrmr->cr[95]) >>
+			     DDRMC_CR95_SWLVL_RESP_1_OFF) & 0xF;
+		if (swlvl_rsp == 0)
+			generic_set_bit(i, rdlvl_rsp);
+	}
+
+	bitmap_print(rdlvl_rsp, DDRMC_DQS_DQ_MAX_DELAY);
+
+	/*
+	 * First test for rising edge 0x0 -> 0x1 in bitmap
+	 */
+	rdlvl_dl_1_min = ddr_cal_get_first_edge_index(rdlvl_rsp, RISING_EDGE,
+						      N_SAMPLES, N_SAMPLES,
+						      DDRMC_DQS_DQ_MAX_DELAY);
+
+	/*
+	 * Secondly test for falling edge 0x1 -> 0x0 in bitmap
+	 */
+	rdlvl_dl_1_max = ddr_cal_get_first_edge_index(rdlvl_rsp, FALLING_EDGE,
+						      N_SAMPLES, rdlvl_dl_1_min,
+						      DDRMC_DQS_DQ_MAX_DELAY);
+
+	debug("RDLVL: DL_1 min: %d [0x%x] DL_1 max: %d [0x%x]\n",
+	      rdlvl_dl_1_min, rdlvl_dl_1_min, rdlvl_dl_1_max, rdlvl_dl_1_max);
+	rdlvl_dl_1 = (rdlvl_dl_1_max - rdlvl_dl_1_min) / 2;
+
+	if (rdlvl_dl_1_max == -1 || rdlvl_dl_1_min == -1 || rdlvl_dl_1 <= 0) {
+		debug("RDLVL: The DQS to DQ delay cannot be found!\n");
+		debug("RDLVL: Using default - slice 1: %d!\n", rdlvl_dl_1_def);
+		rdlvl_dl_1 = rdlvl_dl_1_def;
+	}
+
+	debug("RDLVL: CALIBRATED: rdlvl_dl_0: 0x%x\t rdlvl_dl_1: 0x%x\n",
+	      rdlvl_dl_0, rdlvl_dl_1);
+
+	/* Write new delay values */
+	writel(DDRMC_CR105_RDLVL_DL_0(rdlvl_dl_0), &ddrmr->cr[105]);
+	writel(DDRMC_CR110_RDLVL_DL_1(rdlvl_dl_1), &ddrmr->cr[110]);
+
+	sw_leveling_load_value;
+	sw_leveling_op_done;
+
+	/* Exit procedure - CR94[SWLVL_EXIT] to ’b1 */
+	sw_leveling_exit;
+
+	/* Poll CR94[SWLVL_OP_DONE] */
+	sw_leveling_op_done;
+
+	return 0;
+}
+
+/*
+ * WRLVL_DL calibration:
+ *
+ * For non-flyback memory architecture - where one have a single DDR3 x16
+ * memory - it is NOT necessary to perform "Write Leveling"
+ * [3] 'Vybrid DDR3 write leveling' https://community.nxp.com/thread/429362
+ *
+ */
+
+int ddrmc_calibration(struct ddrmr_regs *ddrmr)
+{
+	ddrmc_cal_dqs_to_dq(ddrmr);
+
+	return 0;
+}

arch/arm/mach-imx/ddrmc-vf610-calibration.h

+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * ddrmc DDR3 calibration code for NXP's VF610
+ *
+ * Copyright (C) 2018 DENX Software Engineering
+ * Lukasz Majewski, DENX Software Engineering, lukma@denx.de
+ *
+ */
+
+#ifndef __DDRMC_VF610_CALIBRATOIN_H_
+#define __DDRMC_VF610_CALIBRATOIN_H_
+
+/*
+ * Number of "samples" in the calibration bitmap
+ * to be considered during calibration.
+ */
+#define N_SAMPLES 3
+
+/*
+ * Constants to indicate if we are looking for a rising or
+ * falling edge in the calibration bitmap
+ */
+enum edge {
+	FALLING_EDGE = 1,
+	RISING_EDGE
+};
+
+/*
+ * The max number of delay elements when DQS to DQ setting
+ */
+#define DDRMC_DQS_DQ_MAX_DELAY 0xFF
+
+/**
+ * ddrmc_calibration - Vybrid's (VF610) DDR3 calibration code
+ *
+ * This function is calculating proper memory controller values
+ * during run time.
+ *
+ * @param ddrmr_regs - memory controller registers
+ *
+ * @return 0 on success, otherwise error code
+ */
+int ddrmc_calibration(struct ddrmr_regs *ddrmr);
+
+#endif /* __DDRMC_VF610_CALIBRATOIN_H_ */