Add SWD protocol support to sysfsgpio

Based on the initial work on bcm2835gpio.c by Paul Fertser with many
additions. Modifications to the GPIO handling was minimal in this
patch. A more big modification is required before cleanup the
interface between bitbang and sysfsgpio.

Change-Id: I54bf2a2aa2ca059368b0e0e105dff6084b73d624
Signed-off-by: Jean-Christian de Rivaz <jc@eclis.ch>
Reviewed-on: http://openocd.zylin.com/2438
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>

src/jtag/drivers/sysfsgpio.c

@@ -16,6 +16,10 @@
  *   Free Software Foundation, Inc.,                                       *
  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.           *
  ***************************************************************************/
+
+/* 2014-12: Addition of the SWD protocol support is based on the initial work
+ * on bcm2835gpio.c by Paul Fertser and modifications by Jean-Christian de Rivaz. */
+
 /**
  * @file
  * This driver implements a bitbang jtag interface using gpio lines via
@@ -139,17 +143,26 @@ static int setup_sysfs_gpio(int gpio, int is_output, int init_high)
 	}
 
 	snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
-	if (is_output)
+	ret = open(buf, O_RDWR | O_NONBLOCK | O_SYNC);
-		ret = open(buf, O_WRONLY | O_NONBLOCK | O_SYNC);
+	if (ret < 0) {
-	else
+		LOG_ERROR("Couldn't open value for gpio %d", gpio);
-		ret = open(buf, O_RDONLY | O_NONBLOCK | O_SYNC);
+		perror("sysfsgpio: ");
-
-	if (ret < 0)
 		unexport_sysfs_gpio(gpio);
+	}
 
 	return ret;
 }
 
+/* gpio numbers for each gpio. Negative values are invalid */
+static int tck_gpio = -1;
+static int tms_gpio = -1;
+static int tdi_gpio = -1;
+static int tdo_gpio = -1;
+static int trst_gpio = -1;
+static int srst_gpio = -1;
+static int swclk_gpio = -1;
+static int swdio_gpio = -1;
+
 /*
  * file descriptors for /sys/class/gpio/gpioXX/value
  * Set up during init.
@@ -160,6 +173,72 @@ static int tdi_fd = -1;
 static int tdo_fd = -1;
 static int trst_fd = -1;
 static int srst_fd = -1;
+static int swclk_fd = -1;
+static int swdio_fd = -1;
+
+static int last_swclk;
+static int last_swdio;
+static bool last_stored;
+static bool swdio_input;
+
+static void sysfsgpio_swdio_drive(bool is_output)
+{
+	char buf[40];
+	int ret;
+
+	snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", swdio_gpio);
+	ret = open_write_close(buf, is_output ? "high" : "in");
+	if (ret < 0) {
+		LOG_ERROR("Couldn't set direction for gpio %d", swdio_gpio);
+		perror("sysfsgpio: ");
+	}
+
+	last_stored = false;
+	swdio_input = !is_output;
+}
+
+static int sysfsgpio_swdio_read(void)
+{
+	char buf[1];
+
+	/* important to seek to signal sysfs of new read */
+	lseek(swdio_fd, 0, SEEK_SET);
+	int ret = read(swdio_fd, &buf, sizeof(buf));
+
+	if (ret < 0) {
+		LOG_WARNING("reading swdio failed");
+		return 0;
+	}
+
+	return buf[0] == '1';
+}
+
+static void sysfsgpio_swdio_write(int swclk, int swdio)
+{
+	const char one[] = "1";
+	const char zero[] = "0";
+
+	size_t bytes_written;
+
+	if (!swdio_input) {
+		if (!last_stored || (swdio != last_swdio)) {
+			bytes_written = write(swdio_fd, swdio ? &one : &zero, 1);
+			if (bytes_written != 1)
+				LOG_WARNING("writing swdio failed");
+		}
+	}
+
+	/* write swclk last */
+	if (!last_stored || (swclk != last_swclk)) {
+		bytes_written = write(swclk_fd, swclk ? &one : &zero, 1);
+		if (bytes_written != 1)
+			LOG_WARNING("writing swclk failed");
+	}
+
+	last_swdio = swdio;
+	last_swclk = swclk;
+	last_stored = true;
+}
 
 /*
  * Bitbang interface read of TDO
@@ -191,6 +270,11 @@ static int sysfsgpio_read(void)
  */
 static void sysfsgpio_write(int tck, int tms, int tdi)
 {
+	if (swd_mode) {
+		sysfsgpio_swdio_write(tck, tdi);
+		return;
+	}
+
 	const char one[] = "1";
 	const char zero[] = "0";
 
@@ -239,6 +323,7 @@ static void sysfsgpio_write(int tck, int tms, int tdi)
  */
 static void sysfsgpio_reset(int trst, int srst)
 {
+	LOG_DEBUG("sysfsgpio_reset");
 	const char one[] = "1";
 	const char zero[] = "0";
 	size_t bytes_written;
@@ -258,14 +343,6 @@ static void sysfsgpio_reset(int trst, int srst)
 	}
 }
 
-/* gpio numbers for each gpio. Negative values are invalid */
-static int tck_gpio = -1;
-static int tms_gpio = -1;
-static int tdi_gpio = -1;
-static int tdo_gpio = -1;
-static int trst_gpio = -1;
-static int srst_gpio = -1;
-
 COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionums)
 {
 	if (CMD_ARGC == 4) {
@@ -338,6 +415,40 @@ COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
 	return ERROR_OK;
 }
 
+COMMAND_HANDLER(sysfsgpio_handle_swd_gpionums)
+{
+	if (CMD_ARGC == 2) {
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swclk_gpio);
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], swdio_gpio);
+	} else if (CMD_ARGC != 0) {
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+
+	command_print(CMD_CTX,
+			"SysfsGPIO nums: swclk = %d, swdio = %d",
+			swclk_gpio, swdio_gpio);
+
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_swd_gpionum_swclk)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swclk_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: swclk = %d", swclk_gpio);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_swd_gpionum_swdio)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swdio_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: swdio = %d", swdio_gpio);
+	return ERROR_OK;
+}
+
 static const struct command_registration sysfsgpio_command_handlers[] = {
 	{
 		.name = "sysfsgpio_jtag_nums",
@@ -382,17 +493,39 @@ static const struct command_registration sysfsgpio_command_handlers[] = {
 		.mode = COMMAND_CONFIG,
 		.help = "gpio number for trst.",
 	},
+	{
+		.name = "sysfsgpio_swd_nums",
+		.handler = &sysfsgpio_handle_swd_gpionums,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio numbers for swclk, swdio. (in that order)",
+		.usage = "(swclk swdio)* ",
+	},
+	{
+		.name = "sysfsgpio_swclk_num",
+		.handler = &sysfsgpio_handle_swd_gpionum_swclk,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for swclk.",
+	},
+	{
+		.name = "sysfsgpio_swdio_num",
+		.handler = &sysfsgpio_handle_swd_gpionum_swdio,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for swdio.",
+	},
 	COMMAND_REGISTRATION_DONE
 };
 
 static int sysfsgpio_init(void);
 static int sysfsgpio_quit(void);
 
+static const char * const sysfsgpio_transports[] = { "jtag", "swd", NULL };
+
 struct jtag_interface sysfsgpio_interface = {
 	.name = "sysfsgpio",
 	.supported = DEBUG_CAP_TMS_SEQ,
 	.execute_queue = bitbang_execute_queue,
-	.transports = jtag_only,
+	.transports = sysfsgpio_transports,
+	.swd = &bitbang_swd,
 	.commands = sysfsgpio_command_handlers,
 	.init = sysfsgpio_init,
 	.quit = sysfsgpio_quit,
@@ -402,6 +535,8 @@ static struct bitbang_interface sysfsgpio_bitbang = {
 	.read = sysfsgpio_read,
 	.write = sysfsgpio_write,
 	.reset = sysfsgpio_reset,
+	.swdio_read = sysfsgpio_swdio_read,
+	.swdio_drive = sysfsgpio_swdio_drive,
 	.blink = 0
 };
 
@@ -426,68 +561,113 @@ static void cleanup_all_fds(void)
 	cleanup_fd(srst_fd, srst_gpio);
 }
 
+static bool sysfsgpio_jtag_mode_possible(void)
+{
+	if (!is_gpio_valid(tck_gpio))
+		return 0;
+	if (!is_gpio_valid(tms_gpio))
+		return 0;
+	if (!is_gpio_valid(tdi_gpio))
+		return 0;
+	if (!is_gpio_valid(tdo_gpio))
+		return 0;
+	return 1;
+}
+
+static bool sysfsgpio_swd_mode_possible(void)
+{
+	if (!is_gpio_valid(swclk_gpio))
+		return 0;
+	if (!is_gpio_valid(swdio_gpio))
+		return 0;
+	return 1;
+}
+
 static int sysfsgpio_init(void)
 {
 	bitbang_interface = &sysfsgpio_bitbang;
 
-	LOG_INFO("SysfsGPIO JTAG bitbang driver");
+	LOG_INFO("SysfsGPIO JTAG/SWD bitbang driver");
 
-	if (!(is_gpio_valid(tck_gpio)
+	if (sysfsgpio_jtag_mode_possible()) {
-			&& is_gpio_valid(tms_gpio)
+		if (sysfsgpio_swd_mode_possible())
-			&& is_gpio_valid(tdi_gpio)
+			LOG_INFO("JTAG and SWD modes enabled");
-			&& is_gpio_valid(tdo_gpio))) {
+		else
-		if (!is_gpio_valid(tck_gpio))
+			LOG_INFO("JTAG only mode enabled (specify swclk and swdio gpio to add SWD mode)");
-			LOG_ERROR("gpio num for tck is invalid");
+		if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
-		if (!is_gpio_valid(tms_gpio))
+			LOG_ERROR("Require at least one of trst or srst gpios to be specified");
-			LOG_ERROR("gpio num for tms is invalid");
+			return ERROR_JTAG_INIT_FAILED;
-		if (!is_gpio_valid(tdo_gpio))
+		}
-			LOG_ERROR("gpio num for tdo is invalid");
+	} else if (sysfsgpio_swd_mode_possible()) {
-		if (!is_gpio_valid(tdi_gpio))
+		LOG_INFO("SWD only mode enabled (specify tck, tms, tdi and tdo gpios to add JTAG mode)");
-			LOG_ERROR("gpio num for tdi is invalid");
+	} else {
-
+		LOG_ERROR("Require tck, tms, tdi and tdo gpios for JTAG mode and/or swclk and swdio gpio for SWD mode");
-		LOG_ERROR("Require tck, tms, tdi and tdo gpios to all be specified");
 		return ERROR_JTAG_INIT_FAILED;
 	}
 
-	if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
-		LOG_ERROR("Require at least one of trst or srst gpios to be specified");
-		return ERROR_JTAG_INIT_FAILED;
-	}
 
 	/*
 	 * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
 	 * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
+	 * For SWD, SWCLK and SWDIO are configures as output high.
 	 */
-	tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
+	if (tck_gpio >= 0) {
-	if (tck_fd < 0)
+		tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
-		goto out_error;
+		if (tck_fd < 0)
+			goto out_error;
+	}
 
-	tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
+	if (tms_gpio >= 0) {
-	if (tms_fd < 0)
+		tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
-		goto out_error;
+		if (tms_fd < 0)
+			goto out_error;
+	}
 
-	tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
+	if (tdi_gpio >= 0) {
-	if (tdi_fd < 0)
+		tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
-		goto out_error;
+		if (tdi_fd < 0)
+			goto out_error;
+	}
 
-	tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
+	if (tdo_gpio >= 0) {
-	if (tdo_fd < 0)
+		tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
-		goto out_error;
+		if (tdo_fd < 0)
+			goto out_error;
+	}
 
 	/* assume active low*/
-	if (trst_gpio > 0) {
+	if (trst_gpio >= 0) {
 		trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
 		if (trst_fd < 0)
 			goto out_error;
 	}
 
 	/* assume active low*/
-	if (srst_gpio > 0) {
+	if (srst_gpio >= 0) {
 		srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
 		if (srst_fd < 0)
 			goto out_error;
 	}
 
+	if (swclk_gpio >= 0) {
+		swclk_fd = setup_sysfs_gpio(swclk_gpio, 1, 0);
+		if (swclk_fd < 0)
+			goto out_error;
+	}
+
+	if (swdio_gpio >= 0) {
+		swdio_fd = setup_sysfs_gpio(swdio_gpio, 1, 0);
+		if (swdio_fd < 0)
+			goto out_error;
+	}
+
+	if (sysfsgpio_swd_mode_possible()) {
+		if (swd_mode)
+			bitbang_swd_switch_seq(NULL, JTAG_TO_SWD);
+		else
+			bitbang_swd_switch_seq(NULL, SWD_TO_JTAG);
+	}
+
 	return ERROR_OK;
 
 out_error: