diff --git a/src/adiv5.c b/src/adiv5.c
index 6e0680e..53e453f 100644
--- a/src/adiv5.c
+++ b/src/adiv5.c
@@ -504,6 +504,9 @@ adiv5_mem_read(ADIv5_AP_t *ap, void *dest, uint32_t src, size_t len)
 	uint32_t osrc = src;
 	enum align align = MIN(ALIGNOF(src), ALIGNOF(len));
 
+	if (len == 0)
+		return;
+
 	len >>= align;
 	ap_mem_access_setup(ap, src, align);
 	adiv5_dp_low_access(ap->dp, ADIV5_LOW_READ, ADIV5_AP_DRW, 0);
diff --git a/src/crc32.c b/src/crc32.c
index 16cc565..881f12d 100644
--- a/src/crc32.c
+++ b/src/crc32.c
@@ -89,23 +89,21 @@ static const uint32_t crc32_table[] = {
 	0xBCB4666D, 0xB8757BDA, 0xB5365D03, 0xB1F740B4,
 };
 
-uint32_t crc32_calc(uint32_t crc, uint8_t data)
+static uint32_t crc32_calc(uint32_t crc, uint8_t data)
 {
 	return (crc << 8) ^ crc32_table[((crc >> 24) ^ data) & 255];
 }
 
-uint32_t generic_crc32(target *t, uint32_t base, int len)
+uint32_t generic_crc32(target *t, uint32_t base, size_t len)
 {
 	uint32_t crc = -1;
-	static uint8_t bytes[128];
+	uint8_t bytes[128];
 
 	while (len) {
-		uint32_t i;
-		uint32_t read_len = len >= 128 ? 128 : len;
-
+		size_t read_len = MIN(sizeof(bytes), len);
 		target_mem_read(t, bytes, base, read_len);
 
-		for (i=0; i<read_len; i++)
+		for (unsigned i = 0; i < read_len; i++)
 			crc = crc32_calc(crc, bytes[i]);
 
 		base += read_len;
@@ -115,29 +113,31 @@ uint32_t generic_crc32(target *t, uint32_t base, int len)
 }
 #else
 #include <libopencm3/stm32/crc.h>
-uint32_t generic_crc32(target *t, uint32_t base, int len)
+uint32_t generic_crc32(target *t, uint32_t base, size_t len)
 {
-	uint32_t data;
+	uint8_t bytes[128];
 	uint32_t crc;
-	size_t i;
 
 	CRC_CR |= CRC_CR_RESET;
 
 	while (len > 3) {
-		data = target_mem_read32(t, base);
+		size_t read_len = MIN(sizeof(bytes), len) & ~3;
+		target_mem_read(t, bytes, base, read_len);
 
-		CRC_DR = __builtin_bswap32(data);
-		base += 4;
-		len -= 4;
+		for (unsigned i = 0; i < read_len; i += 4)
+			CRC_DR = __builtin_bswap32(*(uint32_t*)(bytes+i));
+
+		base += read_len;
+		len -= read_len;
 	}
 
 	crc = CRC_DR;
 
+	target_mem_read(t, bytes, base, len);
+	uint8_t *data = bytes;
 	while (len--) {
-		data = target_mem_read8(t, base++);
-
-		crc ^= data << 24;
-		for (i = 0; i < 8; i++) {
+		crc ^= *data++ << 24;
+		for (int i = 0; i < 8; i++) {
 			if (crc & 0x80000000)
 				crc = (crc << 1) ^ 0x4C11DB7;
 			else
@@ -146,5 +146,5 @@ uint32_t generic_crc32(target *t, uint32_t base, int len)
 	}
 	return crc;
 }
-
 #endif
+
diff --git a/src/include/crc32.h b/src/include/crc32.h
index bd8d5c4..4e0f729 100644
--- a/src/include/crc32.h
+++ b/src/include/crc32.h
@@ -21,7 +21,6 @@
 #ifndef __CRC32_H
 #define __CRC32_H
 
-uint32_t crc32_calc(uint32_t crc, uint8_t data);
 uint32_t generic_crc32(target *t, uint32_t base, int len);
 
 #endif
diff --git a/src/include/target.h b/src/include/target.h
index 16173e9..9436af4 100644
--- a/src/include/target.h
+++ b/src/include/target.h
@@ -53,13 +53,6 @@ bool target_check_error(target *t);
 void target_mem_read(target *t, void *dest, uint32_t src, size_t len);
 void target_mem_write(target *t, uint32_t dest, const void *src, size_t len);
 
-uint32_t target_mem_read32(target *t, uint32_t addr);
-uint16_t target_mem_read16(target *t, uint32_t addr);
-uint8_t target_mem_read8(target *t, uint32_t addr);
-void target_mem_write32(target *t, uint32_t addr, uint32_t value);
-void target_mem_write16(target *t, uint32_t addr, uint16_t value);
-void target_mem_write8(target *t, uint32_t addr, uint8_t value);
-
 /* Register access functions */
 void target_regs_read(target *t, void *data);
 void target_regs_write(target *t, const void *data);
diff --git a/src/target_internal.h b/src/target_internal.h
index ee5d1be..408056f 100644
--- a/src/target_internal.h
+++ b/src/target_internal.h
@@ -118,6 +118,14 @@ int target_flash_write_buffered(struct target_flash *f,
                                 uint32_t dest, const void *src, size_t len);
 int target_flash_done_buffered(struct target_flash *f);
 
+/* Convenience function for MMIO access */
+uint32_t target_mem_read32(target *t, uint32_t addr);
+uint16_t target_mem_read16(target *t, uint32_t addr);
+uint8_t target_mem_read8(target *t, uint32_t addr);
+void target_mem_write32(target *t, uint32_t addr, uint32_t value);
+void target_mem_write16(target *t, uint32_t addr, uint16_t value);
+void target_mem_write8(target *t, uint32_t addr, uint8_t value);
+
 /* Probe for various targets.
  * Actual functions implemented in their respective drivers.
  */