diff --git a/payloads/libpayload/include/libpayload.h b/payloads/libpayload/include/libpayload.h
index 7701a052c2..e08d211983 100644
--- a/payloads/libpayload/include/libpayload.h
+++ b/payloads/libpayload/include/libpayload.h
@@ -472,18 +472,16 @@ static inline int __ffs64(u64 x) { return log2_64(x & (u64)(-(s64)x)); }
  * @defgroup mmio MMIO helper functions
  * @{
  */
-#if !CONFIG(LP_ARCH_MIPS)
 void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
 			int fifo_stride, int fifo_width);
-void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
+void buffer_to_fifo32_prefix(const void *buffer, u32 prefix, int prefsz, size_t size,
 			     void *fifo, int fifo_stride, int fifo_width);
-static inline void buffer_to_fifo32(void *buffer, size_t size, void *fifo,
+static inline void buffer_to_fifo32(const void *buffer, size_t size, void *fifo,
 				    int fifo_stride, int fifo_width)
 {
 	buffer_to_fifo32_prefix(buffer, 0, 0, size, fifo,
 				fifo_stride, fifo_width);
 }
-#endif
 /** @} */
 
 /**
diff --git a/payloads/libpayload/libc/lib.c b/payloads/libpayload/libc/lib.c
index 8387e02a47..77e213c7e0 100644
--- a/payloads/libpayload/libc/lib.c
+++ b/payloads/libpayload/libc/lib.c
@@ -126,7 +126,6 @@ char *getenv(const char *name)
 	return NULL;
 }
 
-#if !CONFIG(LP_ARCH_MIPS)
 /*
  * Reads a transfer buffer from 32-bit FIFO registers. fifo_stride is the
  * distance in bytes between registers (e.g. pass 4 for a normal array of 32-bit
@@ -156,10 +155,10 @@ void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
  * bytes of the 'prefix' u32 parameter and any high-order bytes exceeding prefsz
  * must be 0. Note that 'size' counts total bytes written, including 'prefsz'.
  */
-void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
+void buffer_to_fifo32_prefix(const void *buffer, u32 prefix, int prefsz, size_t size,
 			     void *fifo, int fifo_stride, int fifo_width)
 {
-	u8 *p = buffer;
+	const u8 *p = buffer;
 	int i, j = prefsz;
 
 	assert(fifo_width > 0 && fifo_width <= sizeof(u32) &&
@@ -175,4 +174,3 @@ void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
 	}
 
 }
-#endif
diff --git a/src/device/mmio.c b/src/device/mmio.c
index 8b08b9b2a4..de8c8d3955 100644
--- a/src/device/mmio.c
+++ b/src/device/mmio.c
@@ -21,10 +21,10 @@ void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
 	}
 }
 
-void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
+void buffer_to_fifo32_prefix(const void *buffer, u32 prefix, int prefsz, size_t size,
 			     void *fifo, int fifo_stride, int fifo_width)
 {
-	u8 *p = buffer;
+	const u8 *p = buffer;
 	int i, j = prefsz;
 
 	assert(fifo_width > 0 && fifo_width <= sizeof(u32) &&
diff --git a/src/include/device/mmio.h b/src/include/device/mmio.h
index ca3dfa956e..3c9a83363f 100644
--- a/src/include/device/mmio.h
+++ b/src/include/device/mmio.h
@@ -42,7 +42,7 @@ void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
  * bytes of the 'prefix' u32 parameter and any high-order bytes exceeding prefsz
  * must be 0. Note that 'size' counts total bytes written, including 'prefsz'.
  */
-void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
+void buffer_to_fifo32_prefix(const void *buffer, u32 prefix, int prefsz, size_t size,
 			     void *fifo, int fifo_stride, int fifo_width);
 
 /*
@@ -51,7 +51,7 @@ void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
  * registers or 0 to write everything into the same register). fifo_width is
  * the amount of bytes written per register (can be 1 through 4).
  */
-static inline void buffer_to_fifo32(void *buffer, size_t size, void *fifo,
+static inline void buffer_to_fifo32(const void *buffer, size_t size, void *fifo,
 				    int fifo_stride, int fifo_width)
 {
 	buffer_to_fifo32_prefix(buffer, 0, 0, size, fifo,