RISC-V: Add SBI glue logic

Currently only stubs for mtime handling added, with a gentle reminder
that the actual implementation is still missing.

arch/risc-v/src/common/riscv_internal.h

@@ -250,6 +250,13 @@ int riscv_check_pmp_access(uintptr_t attr, uintptr_t base, uintptr_t size);
 int riscv_configured_pmp_regions(void);
 int riscv_next_free_pmp_region(void);
 
+/* RISC-V SBI wrappers ******************************************************/
+
+#ifdef CONFIG_ARCH_USE_S_MODE
+void riscv_sbi_set_timer(uint64_t stime_value);
+uint64_t riscv_sbi_get_time(void);
+#endif
+
 /* Power management *********************************************************/
 
 #ifdef CONFIG_PM

arch/risc-v/src/common/supervisor/Make.defs

@@ -22,7 +22,7 @@
 
 CMN_ASRCS += riscv_dispatch_syscall.S
 CMN_CSRCS += riscv_perform_syscall.c
-CMN_CSRCS += riscv_percpu.c
+CMN_CSRCS += riscv_percpu.c riscv_sbi.c
 
 INCLUDES += ${shell $(INCDIR) "$(CC)" $(ARCH_SRCDIR)$(DELIM)common$(DELIM)supervisor}
 VPATH += common$(DELIM)supervisor

arch/risc-v/src/common/supervisor/riscv_sbi.c

@@ -0,0 +1,89 @@
+/****************************************************************************
+ * arch/risc-v/src/common/supervisor/riscv_sbi.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/arch.h>
+
+#include <stdint.h>
+
+#include "riscv_internal.h"
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+#ifdef CONFIG_ARCH_RV64
+static inline uint64_t rdtime(void)
+{
+  uint32_t hi;
+  uint32_t lo;
+
+  do
+    {
+      hi = READ_CSR(timeh);
+      lo = READ_CSR(time);
+    }
+  while (hi != READ_CSR(timeh));
+
+  return (((uint64_t) hi) << 32) | lo;
+}
+#else
+#define rdtime() READ_CSR(time)
+#endif /* CONFIG_ARCH_RV64 */
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: riscv_sbi_set_timer
+ *
+ * Description:
+ *   Set new compare match value for timer
+ *
+ * Input Parameters:
+ *   stime_value - Value to set
+ *
+ ****************************************************************************/
+
+void riscv_sbi_set_timer(uint64_t stime_value)
+{
+#error "Missing functionality..."
+}
+
+/****************************************************************************
+ * Name: riscv_sbi_get_time
+ *
+ * Description:
+ *   Get value of mtime
+ *
+ * Return:
+ *   Value of mtime
+ *
+ ****************************************************************************/
+
+uint64_t riscv_sbi_get_time(void)
+{
+  return rdtime();
+}