nxp: added csu driver

NXP Central Security Unit(CSU) for NXP SoC.
CSU is used for:
- Access permissions for peripheral that donot have their own
  access control.
- Locking of individual CSU settings until the next POR
- General purpose security related control bits

Refer NXP SoC manuals fro more details.

Signed-off-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Change-Id: I07a4729c79c5e2597f8b2a782e87e09f7f30c2ca
diff --git a/drivers/nxp/csu/csu.c b/drivers/nxp/csu/csu.c
new file mode 100644
index 0000000..9f90fe0
--- /dev/null
+++ b/drivers/nxp/csu/csu.c
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2020 NXP
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#include <endian.h>
+
+#include <common/debug.h>
+#include <csu.h>
+#include <lib/mmio.h>
+
+void enable_layerscape_ns_access(struct csu_ns_dev_st *csu_ns_dev,
+				 uint32_t num, uintptr_t nxp_csu_addr)
+{
+	uint32_t *base = (uint32_t *)nxp_csu_addr;
+	uint32_t *reg;
+	uint32_t val;
+	int i;
+
+	for (i = 0; i < num; i++) {
+		reg = base + csu_ns_dev[i].ind / 2U;
+		val = be32toh(mmio_read_32((uintptr_t)reg));
+		if (csu_ns_dev[i].ind % 2U == 0U) {
+			val &= 0x0000ffffU;
+			val |= csu_ns_dev[i].val << 16U;
+		} else {
+			val &= 0xffff0000U;
+			val |= csu_ns_dev[i].val;
+		}
+		mmio_write_32((uintptr_t)reg, htobe32(val));
+	}
+}