diff --git a/drivers/renesas/rzg/qos/qos_common.h b/drivers/renesas/rzg/qos/qos_common.h
new file mode 100644
index 0000000..6e0cf0e
--- /dev/null
+++ b/drivers/renesas/rzg/qos/qos_common.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2021, Renesas Electronics Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef QOS_COMMON_H
+#define QOS_COMMON_H
+
+#define RCAR_REF_DEFAULT		0U
+
+/* define used for get_refperiod. */
+/* REFPERIOD_CYCLE need smaller than QOSWT_WTSET0_CYCLEs */
+#if (RCAR_REF_INT == RCAR_REF_DEFAULT)	/* REF default */
+#define REFPERIOD_CYCLE		/* unit:ns */	\
+	((126U * BASE_SUB_SLOT_NUM * 1000U) / 400U)
+#else					/* REF option */
+#define REFPERIOD_CYCLE		/* unit:ns */	\
+	((252U * BASE_SUB_SLOT_NUM * 1000U) / 400U)
+#endif
+
+#if (RCAR_LSI == RCAR_AUTO) || (RCAR_LSI == RZ_G2M)
+/* define used for G2M */
+#if (RCAR_REF_INT == RCAR_REF_DEFAULT)	/* REF 1.95usec */
+#define SUB_SLOT_CYCLE_G2M_11		0x7EU	/* 126 */
+#define SUB_SLOT_CYCLE_G2M_30		0x7EU	/* 126 */
+#else /* REF 3.9usec */
+#define SUB_SLOT_CYCLE_G2M_11		0xFCU	/* 252 */
+#define SUB_SLOT_CYCLE_G2M_30		0xFCU	/* 252 */
+#endif /* (RCAR_REF_INT == RCAR_REF_DEFAULT) */
+
+#define SL_INIT_SSLOTCLK_G2M_11		(SUB_SLOT_CYCLE_G2M_11 - 1U)
+#define SL_INIT_SSLOTCLK_G2M_30		(SUB_SLOT_CYCLE_G2M_30 - 1U)
+#define QOSWT_WTSET0_CYCLE_G2M_11	/* unit:ns */	\
+	((SUB_SLOT_CYCLE_G2M_11 * BASE_SUB_SLOT_NUM * 1000U) / OPERATING_FREQ)
+#define QOSWT_WTSET0_CYCLE_G2M_30	/* unit:ns */	\
+	((SUB_SLOT_CYCLE_G2M_30 * BASE_SUB_SLOT_NUM * 1000U) / OPERATING_FREQ)
+#endif
+
+#define OPERATING_FREQ			400U	/* MHz */
+#define BASE_SUB_SLOT_NUM		0x6U
+#define SUB_SLOT_CYCLE			0x7EU	/* 126 */
+
+#define QOSWT_WTSET0_CYCLE		/* unit:ns */	\
+	((SUB_SLOT_CYCLE * BASE_SUB_SLOT_NUM * 1000U) / OPERATING_FREQ)
+
+#define SL_INIT_REFFSSLOT		(0x3U << 24U)
+#define SL_INIT_SLOTSSLOT		((BASE_SUB_SLOT_NUM - 1U) << 16U)
+#define SL_INIT_SSLOTCLK		(SUB_SLOT_CYCLE - 1U)
+
+typedef struct {
+	uintptr_t addr;
+	uint64_t value;
+} mstat_slot_t;
+
+struct rcar_gen3_dbsc_qos_settings {
+	uint32_t	reg;
+	uint32_t	val;
+};
+
+extern uint32_t qos_init_ddr_ch;
+extern uint8_t qos_init_ddr_phyvalid;
+
+void rzg_qos_dbsc_setting(const struct rcar_gen3_dbsc_qos_settings *qos,
+			  unsigned int qos_size, bool dbsc_wren);
+
+#endif /* QOS_COMMON_H */