From e2c89ec0f54758c8271e4967fc53bab3b7be9360 Mon Sep 17 00:00:00 2001
From: guozhanxin <guozhanxin@rt-thread.com>
Date: Mon, 4 Jun 2018 14:54:07 +0800
Subject: [PATCH] =?UTF-8?q?[components][cputime]to=20be=20able=20trace=20b?=
 =?UTF-8?q?efore=20use=20DWT.|=E4=BD=BF=E7=94=A8=20DWT=20=E4=B9=8B?=
 =?UTF-8?q?=E5=89=8D=E5=BF=85=E9=A1=BB=E5=85=88=E4=BD=BF=E8=83=BD=E8=B7=9F?=
 =?UTF-8?q?=E8=B8=AA=E7=B3=BB=E7=BB=9F.?=
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---
 components/drivers/cputime/cputime_cortexm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/components/drivers/cputime/cputime_cortexm.c b/components/drivers/cputime/cputime_cortexm.c
index f576df785f..99dc8b013e 100644
--- a/components/drivers/cputime/cputime_cortexm.c
+++ b/components/drivers/cputime/cputime_cortexm.c
@@ -54,6 +54,9 @@ int cortexm_cputime_init(void)
     /* check support bit */
     if ((DWT->CTRL & (1UL << DWT_CTRL_NOCYCCNT_Pos)) == 0) 
     {
+        /* enable trace*/
+        CoreDebug->DEMCR |= (1UL << CoreDebug_DEMCR_TRCENA_Pos);
+        
         /* whether cycle counter not enabled */
         if ((DWT->CTRL & (1UL << DWT_CTRL_CYCCNTENA_Pos)) == 0) 
         {