drivers: ddr: introduce DDR driver for i.MX8M

Introduce DDR driver for i.MX8M. The driver will be used by SPL to
initialze DDR PHY and DDR Controller.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/ddr/imx/imx8m/ddrphy_train.c b/drivers/ddr/imx/imx8m/ddrphy_train.c
new file mode 100644
index 0000000..18f7ed7
--- /dev/null
+++ b/drivers/ddr/imx/imx8m/ddrphy_train.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2018 NXP
+ */
+
+#include <common.h>
+#include <linux/kernel.h>
+#include <asm/arch/ddr.h>
+#include <asm/arch/lpddr4_define.h>
+
+void ddr_cfg_phy(struct dram_timing_info *dram_timing)
+{
+	struct dram_cfg_param *dram_cfg;
+	struct dram_fsp_msg *fsp_msg;
+	unsigned int num;
+	int i = 0;
+	int j = 0;
+
+	/* initialize PHY configuration */
+	dram_cfg = dram_timing->ddrphy_cfg;
+	num  = dram_timing->ddrphy_cfg_num;
+	for (i = 0; i < num; i++) {
+		/* config phy reg */
+		dwc_ddrphy_apb_wr(dram_cfg->reg, dram_cfg->val);
+		dram_cfg++;
+	}
+
+	/* load the frequency setpoint message block config */
+	fsp_msg = dram_timing->fsp_msg;
+	for (i = 0; i < dram_timing->fsp_msg_num; i++) {
+		debug("DRAM PHY training for %dMTS\n", fsp_msg->drate);
+		/* set dram PHY input clocks to desired frequency */
+		ddrphy_init_set_dfi_clk(fsp_msg->drate);
+
+		/* load the dram training firmware image */
+		dwc_ddrphy_apb_wr(0xd0000, 0x0);
+		ddr_load_train_firmware(fsp_msg->fw_type);
+
+		/* load the frequency set point message block parameter */
+		dram_cfg = fsp_msg->fsp_cfg;
+		num = fsp_msg->fsp_cfg_num;
+		for (j = 0; j < num; j++) {
+			dwc_ddrphy_apb_wr(dram_cfg->reg, dram_cfg->val);
+			dram_cfg++;
+		}
+
+		/*
+		 * -------------------- excute the firmware --------------------
+		 * Running the firmware is a simply process to taking the
+		 * PMU out of reset and stall, then the firwmare will be run
+		 * 1. reset the PMU;
+		 * 2. begin the excution;
+		 * 3. wait for the training done;
+		 * 4. read the message block result.
+		 * -------------------------------------------------------------
+		 */
+		dwc_ddrphy_apb_wr(0xd0000, 0x1);
+		dwc_ddrphy_apb_wr(0xd0099, 0x9);
+		dwc_ddrphy_apb_wr(0xd0099, 0x1);
+		dwc_ddrphy_apb_wr(0xd0099, 0x0);
+
+		/* Wait for the training firmware to complete */
+		wait_ddrphy_training_complete();
+
+		/* Halt the microcontroller. */
+		dwc_ddrphy_apb_wr(0xd0099, 0x1);
+
+		/* Read the Message Block results */
+		dwc_ddrphy_apb_wr(0xd0000, 0x0);
+		ddrphy_init_read_msg_block(fsp_msg->fw_type);
+		dwc_ddrphy_apb_wr(0xd0000, 0x1);
+
+		fsp_msg++;
+	}
+
+	/* Load PHY Init Engine Image */
+	dram_cfg = dram_timing->ddrphy_pie;
+	num = dram_timing->ddrphy_pie_num;
+	for (i = 0; i < num; i++) {
+		dwc_ddrphy_apb_wr(dram_cfg->reg, dram_cfg->val);
+		dram_cfg++;
+	}
+
+	/* save the ddr PHY trained CSR in memory for low power use */
+	ddrphy_trained_csr_save(ddrphy_trained_csr, ddrphy_trained_csr_num);
+}