Fix: extract method for SWD parity calculation

src/include/general.h

@@ -48,7 +48,6 @@
 #include <inttypes.h>
 #include <sys/types.h>
 
-#include "maths_utils.h"
 #include "timing.h"
 #include "platform_support.h"
 #include "align.h"

src/include/maths_utils.h

@@ -37,5 +37,6 @@
 #include <stdint.h>
 
 uint8_t ulog2(uint32_t value);
+uint8_t calculate_odd_parity(uint32_t value);
 
 #endif /* INCLUDE_MATHS_UTILS_H */

src/maths_utils.c

@@ -74,3 +74,21 @@ uint8_t ulog2(uint32_t value)
 	return (sizeof(uint8_t) * 8U) - result;
 #endif
 }
+
+uint8_t calculate_odd_parity(const uint32_t value)
+{
+#if defined(__GNUC__)
+	/* Ask for the libgcc impl */
+	return __builtin_parity(value);
+#elif defined(_MSC_VER)
+	/* Ask for a CPU insn */
+	return __popcount(value) & 1U;
+#else
+	/* Generic impl */
+	uint8_t result = 0;
+	for (uint32_t bit = 0; bit < 32; ++bit)
+		result ^= (value >> bit) & 1U;
+
+	return result;
+#endif
+}

src/platforms/common/swdptap.c

@@ -24,6 +24,7 @@
 #include "platform.h"
 #include "timing.h"
 #include "swd.h"
+#include "maths_utils.h"
 
 #if !defined(SWDIO_IN_PORT)
 #define SWDIO_IN_PORT SWDIO_PORT
@@ -130,8 +131,8 @@ static bool swdptap_seq_in_parity(uint32_t *ret, size_t clock_cycles)
 	for (volatile uint32_t counter = target_clk_divider + 1; counter > 0; --counter)
 		continue;
 
-	size_t parity = __builtin_popcount(result);
-	parity += gpio_get(SWDIO_IN_PORT, SWDIO_IN_PIN) ? 1U : 0U;
+	const bool parity = calculate_odd_parity(result);
+	const bool bit = gpio_get(SWDIO_IN_PORT, SWDIO_IN_PIN);
 
 	gpio_set(SWCLK_PORT, SWCLK_PIN);
 	for (volatile uint32_t counter = target_clk_divider + 1; counter > 0; --counter)
@@ -140,7 +141,7 @@ static bool swdptap_seq_in_parity(uint32_t *ret, size_t clock_cycles)
 	*ret = result;
 	/* Terminate the read cycle now */
 	swdptap_turnaround(SWDIO_STATUS_DRIVE);
-	return parity & 1U;
+	return parity != bit;
 }
 
 static void swdptap_seq_out_clk_delay(uint32_t tms_states, size_t clock_cycles) __attribute__((optimize(3)));
@@ -182,9 +183,9 @@ static void swdptap_seq_out(const uint32_t tms_states, const size_t clock_cycles
 
 static void swdptap_seq_out_parity(const uint32_t tms_states, const size_t clock_cycles)
 {
-	int parity = __builtin_popcount(tms_states);
+	const bool parity = calculate_odd_parity(tms_states);
 	swdptap_seq_out(tms_states, clock_cycles);
-	gpio_set_val(SWDIO_PORT, SWDIO_PIN, parity & 1U);
+	gpio_set_val(SWDIO_PORT, SWDIO_PIN, parity);
 	for (volatile uint32_t counter = target_clk_divider + 1; counter > 0; --counter)
 		continue;
 	gpio_set(SWCLK_PORT, SWCLK_PIN);

src/platforms/hosted/dap_swd.c

@@ -34,6 +34,7 @@
 #include "dap.h"
 #include "dap_command.h"
 #include "buffer_utils.h"
+#include "maths_utils.h"
 
 typedef enum dap_swd_turnaround_cycles {
 	DAP_SWD_TURNAROUND_1_CYCLE = 0U,
@@ -127,7 +128,7 @@ static void dap_swd_seq_out_parity(const uint32_t tms_states, const size_t clock
 		DAP_SWD_OUT_SEQUENCE,
 	};
 	write_le4(sequence.data, 0, tms_states);
-	sequence.data[4] = __builtin_parity(tms_states);
+	sequence.data[4] = calculate_odd_parity(tms_states);
 	/* And perform it */
 	if (!perform_dap_swd_sequences(&sequence, 1U))
 		DEBUG_ERROR("dap_swd_seq_out_parity failed\n");
@@ -169,7 +170,7 @@ static bool dap_swd_seq_in_parity(uint32_t *const result, const size_t clock_cyc
 	for (size_t offset = 0; offset < clock_cycles; offset += 8U)
 		data |= sequence.data[offset >> 3U] << offset;
 	*result = data;
-	uint8_t parity = __builtin_parity(data) & 1U;
+	uint8_t parity = calculate_odd_parity(data);
 	parity ^= sequence.data[4] & 1U;
 	return !parity;
 }
@@ -194,7 +195,7 @@ static bool dap_write_reg_no_check(const uint16_t addr, const uint32_t data)
 			33U,
 			DAP_SWD_OUT_SEQUENCE,
 			/* The 4 data bytes are filled in below with write_le4() */
-			{0U, 0U, 0U, 0U, __builtin_parity(data)},
+			{0U, 0U, 0U, 0U, calculate_odd_parity(data)},
 		},
 	};
 	write_le4(sequences[3].data, 0, data);

src/platforms/hosted/ftdi_swd.c

@@ -32,6 +32,7 @@
 #include <ftdi.h>
 #include "ftdi_bmp.h"
 #include "buffer_utils.h"
+#include "maths_utils.h"
 
 typedef enum swdio_status {
 	SWDIO_STATUS_DRIVE,
@@ -237,7 +238,9 @@ static bool ftdi_swd_seq_in_parity_mpsse(uint32_t *const result, const size_t cl
 	uint8_t data_out[5U] = {0};
 	ftdi_jtag_tdi_tdo_seq(data_out, false, NULL, clock_cycles + 1U);
 	const uint32_t data = read_le4(data_out, 0);
-	uint8_t parity = __builtin_parity(data & ((UINT64_C(1) << clock_cycles) - 1U));
+	/* NB: This calculation must be done in 64-bit space due to `1U << 32U` value of 0x00000001'00000000ULL */
+	const uint32_t bitmask = (UINT64_C(1) << clock_cycles) - 1U;
+	uint8_t parity = calculate_odd_parity(data & bitmask);
 	parity ^= data_out[4] & 1U;
 	DEBUG_PROBE("%s %zu clock_cycles: %08" PRIx32 " %s\n", __func__, clock_cycles, data, parity ? "ERR" : "OK");
 	*result = data;
@@ -428,7 +431,7 @@ static void ftdi_swd_seq_out_parity(uint32_t tms_states, size_t clock_cycles)
 {
 	if (clock_cycles > 32U)
 		return;
-	const uint8_t parity = __builtin_parity(tms_states) & 1U;
+	const uint8_t parity = calculate_odd_parity(tms_states);
 	ftdi_swd_turnaround(SWDIO_STATUS_DRIVE);
 	if (do_mpsse)
 		ftdi_swd_seq_out_parity_mpsse(tms_states, parity, clock_cycles);

src/platforms/hosted/jlink_swd.c

@@ -34,6 +34,7 @@
 #include "jlink.h"
 #include "jlink_protocol.h"
 #include "buffer_utils.h"
+#include "maths_utils.h"
 #include "cli.h"
 
 /*
@@ -121,7 +122,7 @@ static void jlink_swd_seq_out_parity(const uint32_t tms_states, const size_t clo
 	/* Construct the parity bit */
 	const size_t byte = clock_cycles >> 3U;
 	const uint8_t bit = clock_cycles & 7U;
-	data[byte] |= (__builtin_parity(tms_states) & 1U) << bit;
+	data[byte] |= calculate_odd_parity(tms_states) << bit;
 	/* Attempt the transfer */
 	if (!jlink_transfer_swd(clock_cycles + 1U, JLINK_SWD_OUT, data, NULL)) {
 		/* If things go wrong, report it */
@@ -159,9 +160,9 @@ static bool jlink_swd_seq_in_parity(uint32_t *const result, const size_t clock_c
 	/* Compute the parity and validate it */
 	const size_t byte = clock_cycles >> 3U;
 	const uint8_t bit = clock_cycles & 7U;
-	uint8_t parity = __builtin_parity(data) & 1U;
+	uint8_t parity = calculate_odd_parity(data);
 	parity ^= (data_out[byte] >> bit) & 1U;
-	/* Retrn the result of the calculation */
+	/* Return the result of the calculation */
 	DEBUG_PROBE("%s %zu clock_cycles: %08" PRIx32 " %s\n", __func__, clock_cycles, data, parity ? "ERR" : "OK");
 	*result = data;
 	return !parity;
@@ -183,7 +184,7 @@ static bool jlink_adiv5_raw_write_no_check(const uint16_t addr, const uint32_t d
 	/* Build the response payload buffer */
 	uint8_t response[6] = {0};
 	write_le4(response, 0, data);
-	response[4] = __builtin_popcount(data) & 1U;
+	response[4] = calculate_odd_parity(data);
 	/* Try sending the data to the device */
 	if (!jlink_transfer(33U + 8U, jlink_adiv5_write_request, response, NULL)) {
 		DEBUG_ERROR("jlink_adiv5_raw_write_no_check failed\n");
@@ -213,7 +214,7 @@ static uint32_t jlink_adiv5_raw_read_no_check(const uint16_t addr)
 	/* Extract the data phase and return it if the transaction succeeded */
 	const uint32_t data = read_le4(response, 0);
 	DEBUG_PROBE("jlink_adiv5_raw_read_no_check %04x -> %08" PRIx32 " %s\n", addr, data,
-		__builtin_parity(data) ^ response[4] ? "ERR" : "OK");
+		calculate_odd_parity(data) != response[4] ? "ERR" : "OK");
 	return ack == SWDP_ACK_OK ? data : 0U;
 }
 
@@ -228,7 +229,7 @@ static uint32_t jlink_adiv5_raw_read(adiv5_debug_port_s *const dp)
 	/* Extract the data phase */
 	const uint32_t response = read_le4(result, 0);
 	/* Calculate and do a parity check */
-	uint8_t parity = __builtin_parity(response) & 1U;
+	uint8_t parity = calculate_odd_parity(response);
 	parity ^= result[4] & 1U;
 	/* If that fails, turn it into an error */
 	if (parity) {
@@ -244,7 +245,7 @@ static uint32_t jlink_adiv5_raw_write(const uint32_t request_value)
 	/* Build the response payload buffer */
 	uint8_t request[6] = {0};
 	write_le4(request, 0, request_value);
-	request[4] = __builtin_popcount(request_value) & 1U;
+	request[4] = calculate_odd_parity(request_value);
 	/* Allocate storage for the result */
 	uint8_t result[6] = {0};
 	/* Try sending the data to the device */

src/platforms/hosted/stlinkv2.c

@@ -35,6 +35,7 @@
 #include "exception.h"
 #include "cortexm.h"
 #include "buffer_utils.h"
+#include "maths_utils.h"
 
 #include <assert.h>
 #include <unistd.h>

src/target/cortexm.c

@@ -42,6 +42,7 @@
 #include "gdb_packet.h"
 #include "semihosting.h"
 #include "platform.h"
+#include "maths_utils.h"
 
 #include <string.h>
 #include <assert.h>