diff --git a/components/drivers/include/drivers/mmcsd_core.h b/components/drivers/include/drivers/mmcsd_core.h
index 1f7b38795ceabef54c35ab81b3c11fb29b6175dc..5326425bfdf44a003c60053ee8038c2bfb566e68 100644
--- a/components/drivers/include/drivers/mmcsd_core.h
+++ b/components/drivers/include/drivers/mmcsd_core.h
@@ -210,37 +210,6 @@ rt_inline rt_uint32_t fls(rt_uint32_t val)
 	return bit;
 }
 
-#if !defined(__GNUC__) || defined(__CC_ARM)
-rt_inline rt_uint32_t ffs(rt_uint32_t x)
-{
-        int r = 1;
-
-        if (!x)
-                return 0;
-        if (!(x & 0xffff)) {
-                x >>= 16;
-                r += 16;
-        }
-        if (!(x & 0xff)) {
-                x >>= 8;
-                r += 8;
-        }
-        if (!(x & 0xf)) {
-                x >>= 4;
-                r += 4;
-        }
-        if (!(x & 3)) {
-                x >>= 2;
-                r += 2;
-        }
-        if (!(x & 1)) {
-                x >>= 1;
-                r += 1;
-        }
-        return r;
-}
-#endif
-
 void mmcsd_host_lock(struct rt_mmcsd_host *host);
 void mmcsd_host_unlock(struct rt_mmcsd_host *host);
 void mmcsd_req_complete(struct rt_mmcsd_host *host);
diff --git a/components/drivers/sdio/mmcsd_core.c b/components/drivers/sdio/mmcsd_core.c
index e9a2e49115aab13761fe7d1c31cf53f986c2eaac..db93cdb10cd6114f9e76997b4d33c9b457142f7f 100644
--- a/components/drivers/sdio/mmcsd_core.c
+++ b/components/drivers/sdio/mmcsd_core.c
@@ -493,7 +493,7 @@ rt_uint32_t mmcsd_select_voltage(struct rt_mmcsd_host *host, rt_uint32_t ocr)
 
 	ocr &= host->valid_ocr;
 
-	bit = ffs(ocr);
+	bit = __rt_ffs(ocr);
 	if (bit) 
 	{
 		bit -= 1;