创建，添加sdram

rt-thread/libcpu/risc-v/t-head/c906/asm/sbiasm.h

@@ -0,0 +1,10 @@
+#ifndef _SBI_ASM_H
+#define _SBI_ASM_H
+
+.macro SBI_CALL which
+    li a7, \which
+    ecall
+    nop
+.endm
+
+#endif /* _SBI_ASM_H */

rt-thread/libcpu/risc-v/t-head/c906/asm/sbidef.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2019-2020, Xim
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+#ifndef _ASM_SBI_DEF_H
+#define _ASM_SBI_DEF_H
+
+#define SBI_SET_TIMER 0
+#define SBI_CONSOLE_PUTCHAR 1
+#define SBI_CONSOLE_GETCHAR 2
+#define SBI_CLEAR_IPI 3
+#define SBI_SEND_IPI 4
+#define SBI_REMOTE_FENCE_I 5
+#define SBI_REMOTE_SFENCE_VMA 6
+#define SBI_REMOTE_SFENCE_VMA_ASID 7
+#define SBI_SHUTDOWN 8
+
+#define SBI_CONSOLE_PUTSTR 9
+
+#define SBI_SD_WRITE 10
+#define SBI_SD_READ 11
+#define SBI_NET_WRITE 12
+#define SBI_NET_READ 13
+
+#endif /* _ASM_SBI_DEF_H */