From 62effc6bfe4f1a7e8a771c49966c4ab7755d6612 Mon Sep 17 00:00:00 2001
From: Palmer Dabbelt <palmer@dabbelt.com>
Date: Fri, 28 Jul 2017 14:10:20 -0700
Subject: Allow the platform to disable HTIF

---
 machine/mtrap.c               | 13 ++++++++++---
 platform/platform_interface.h |  3 +++
 platform/spike.c              |  6 +++++-
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/machine/mtrap.c b/machine/mtrap.c
index d0c1684..ff4eb60 100644
--- a/machine/mtrap.c
+++ b/machine/mtrap.c
@@ -7,6 +7,7 @@
 #include "uart.h"
 #include "fdt.h"
 #include "unprivileged_memory.h"
+#include "platform_interface.h"
 #include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
@@ -20,7 +21,7 @@ static uintptr_t mcall_console_putchar(uint8_t ch)
 {
   if (uart) {
     uart_putchar(ch);
-  } else {
+  } else if (platform__use_htif()) {
     htif_console_putchar(ch);
   }
   return 0;
@@ -28,7 +29,11 @@ static uintptr_t mcall_console_putchar(uint8_t ch)
 
 void poweroff()
 {
-  htif_poweroff();
+  if (platform__use_htif()) {
+    htif_poweroff();
+  } else {
+    while (1);
+  }
 }
 
 void putstring(const char* s)
@@ -61,8 +66,10 @@ static uintptr_t mcall_console_getchar()
 {
   if (uart) {
     return uart_getchar();
-  } else {
+  } else if (platform__use_htif()) {
     return htif_console_getchar();
+  } else {
+    return '\0';
   }
 }
 
diff --git a/platform/platform_interface.h b/platform/platform_interface.h
index 9c52cde..dd521e3 100644
--- a/platform/platform_interface.h
+++ b/platform/platform_interface.h
@@ -15,4 +15,7 @@
  * This will be printed when BBL boots. */
 const char *platform__get_logo(void);
 
+/* Returns TRUE if it's valid to use the HTIF */
+int platform__use_htif(void);
+
 #endif
diff --git a/platform/spike.c b/platform/spike.c
index 06aa742..159255f 100644
--- a/platform/spike.c
+++ b/platform/spike.c
@@ -25,8 +25,12 @@ static const char logo[] =
 "\n"
 "       INSTRUCTION SETS WANT TO BE FREE\n";
 
-
 const char *platform__get_logo(void)
 {
   return logo;
 }
+
+int platform__use_htif(void)
+{
+  return 1;
+}
-- 
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