drivers: new jtag bitbang driver using sysfs gpio

This driver implements a bitbang jtag interface using gpio lines exported via
sysfs.

The aim of this driver implementation is to use system GPIOs but to avoid the
need for an additional kernel driver.

A config suitable for RaspberryPi is included.

Change-Id: Ib2acf720247a219768d1cbfeebd88057ed2d7b8b
Signed-off-by: Marc Reilly <marc@cpdesign.com.au>
Reviewed-on: http://openocd.zylin.com/762
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

3 files changed, 514 insertions, 0 deletions

diff --git a/src/jtag/drivers/Makefile.am b/src/jtag/drivers/Makefile.am
index b02c353..d137713 100644
--- a/src/jtag/drivers/Makefile.am
+++ b/src/jtag/drivers/Makefile.am
@@ -107,6 +107,9 @@ endif
 if OPENDOUS
 DRIVERFILES += opendous.c
 endif
+if SYSFSGPIO
+DRIVERFILES += sysfsgpio.c
+endif
 
 noinst_HEADERS = \
 	bitbang.h \
diff --git a/src/jtag/drivers/sysfsgpio.c b/src/jtag/drivers/sysfsgpio.c
new file mode 100644
index 0000000..05d9a9d
--- /dev/null
+++ b/src/jtag/drivers/sysfsgpio.c
@@ -0,0 +1,505 @@
+/***************************************************************************
+ *   Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
+ ***************************************************************************/
+/**
+ * @file
+ * This driver implements a bitbang jtag interface using gpio lines via
+ * sysfs.
+ * The aim of this driver implementation is use system GPIOs but avoid the
+ * need for a additional kernel driver.
+ * (Note memory mapped IO is another option, however it doesn't mix well with
+ * the kernel gpiolib driver - which makes sense I guess.)
+ *
+ * A gpio is required for tck, tms, tdi and tdo. One or both of srst and trst
+ * must be also be specified. The required jtag gpios are specified via the
+ * sysfsgpio_jtag_nums command or the relevant sysfsgpio_XXX_num commang.
+ * The srst and trst gpios are set via the sysfsgpio_srst_num and
+ * sysfsgpio_trst_num respectively. GPIO numbering follows the kernel
+ * convention of starting from 0.
+ *
+ * The gpios should not be in use by another entity, and must not be requested
+ * by a kernel driver without also being exported by it (otherwise they can't
+ * be exported by sysfs).
+ *
+ * The sysfs gpio interface can only manipulate one gpio at a time, so the
+ * bitbang write handler remembers the last state for tck, tms, tdi to avoid
+ * superfluous writes.
+ * For speed the sysfs "value" entry is opened at init and held open.
+ * This results in considerable gains over open-write-close (45s vs 900s)
+ *
+ * Further work could address:
+ *  -srst and trst open drain/ push pull
+ *  -configurable active high/low for srst & trst
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <jtag/interface.h>
+#include "bitbang.h"
+
+/*
+ * Helper func to determine if gpio number valid
+ *
+ * Assume here that there will be less than 1000 gpios on a system
+ */
+static int is_gpio_valid(int gpio)
+{
+	return gpio >= 0 && gpio < 1000;
+}
+
+/*
+ * Helper func to open, write to and close a file
+ * name and valstr must be null terminated.
+ *
+ * Returns negative on failure.
+ */
+static int open_write_close(const char *name, const char *valstr)
+{
+	int ret;
+	int fd = open(name, O_WRONLY);
+	if (fd < 0)
+		return fd;
+
+	ret = write(fd, valstr, strlen(valstr));
+	close(fd);
+
+	return ret;
+}
+
+/*
+ * Helper func to unexport gpio from sysfs
+ */
+static void unexport_sysfs_gpio(int gpio)
+{
+	char gpiostr[4];
+
+	if (!is_gpio_valid(gpio))
+		return;
+
+	snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
+	if (open_write_close("/sys/class/gpio/unexport", gpiostr) < 0)
+		LOG_ERROR("Couldn't unexport gpio %d", gpio);
+
+	return;
+}
+
+/*
+ * Exports and sets up direction for gpio.
+ * If the gpio is an output, it is initialized according to init_high,
+ * otherwise it is ignored.
+ *
+ * If the gpio is already exported we just show a warning and continue; if
+ * openocd happened to crash (or was killed by user) then the gpios will not
+ * have been cleaned up.
+ */
+static int setup_sysfs_gpio(int gpio, int is_output, int init_high)
+{
+	char buf[40];
+	char gpiostr[4];
+	int ret;
+
+	if (!is_gpio_valid(gpio))
+		return ERROR_OK;
+
+	snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
+	ret = open_write_close("/sys/class/gpio/export", gpiostr);
+	if (ret < 0) {
+		if (errno == EBUSY) {
+			LOG_WARNING("gpio %d is already exported", gpio);
+		} else {
+			LOG_ERROR("Couldn't export gpio %d", gpio);
+			perror("sysfsgpio: ");
+			return ERROR_FAIL;
+		}
+	}
+
+	snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);
+	ret = open_write_close(buf, is_output ? (init_high ? "high" : "low") : "in");
+	if (ret < 0) {
+		LOG_ERROR("Couldn't set direction for gpio %d", gpio);
+		perror("sysfsgpio: ");
+		unexport_sysfs_gpio(gpio);
+		return ERROR_FAIL;
+	}
+
+	snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
+	if (is_output)
+		ret = open(buf, O_WRONLY | O_NONBLOCK | O_SYNC);
+	else
+		ret = open(buf, O_RDONLY | O_NONBLOCK | O_SYNC);
+
+	if (ret < 0)
+		unexport_sysfs_gpio(gpio);
+
+	return ret;
+}
+
+/*
+ * file descriptors for /sys/class/gpio/gpioXX/value
+ * Set up during init.
+ */
+static int tck_fd = -1;
+static int tms_fd = -1;
+static int tdi_fd = -1;
+static int tdo_fd = -1;
+static int trst_fd = -1;
+static int srst_fd = -1;
+
+/*
+ * Bitbang interface read of TDO
+ *
+ * The sysfs value will read back either '0' or '1'. The trick here is to call
+ * lseek to bypass buffering in the sysfs kernel driver.
+ */
+static int sysfsgpio_read(void)
+{
+	char buf[1];
+
+	/* important to seek to signal sysfs of new read */
+	lseek(tdo_fd, 0, SEEK_SET);
+	int ret = read(tdo_fd, &buf, sizeof(buf));
+
+	if (ret < 0) {
+		LOG_WARNING("reading tdo failed");
+		return 0;
+	}
+
+	return buf[0] == '1';
+}
+
+/*
+ * Bitbang interface write of TCK, TMS, TDI
+ *
+ * Seeing as this is the only function where the outputs are changed,
+ * we can cache the old value to avoid needlessly writing it.
+ */
+static void sysfsgpio_write(int tck, int tms, int tdi)
+{
+	const char one[] = "1";
+	const char zero[] = "0";
+
+	static int last_tck;
+	static int last_tms;
+	static int last_tdi;
+
+	static int first_time;
+
+	if (!first_time) {
+		last_tck = !tck;
+		last_tms = !tms;
+		last_tdi = !tdi;
+		first_time = 1;
+	}
+
+	if (tdi != last_tdi)
+		write(tdi_fd, tdi ? &one : &zero, 1);
+	if (tms != last_tms)
+		write(tms_fd, tms ? &one : &zero, 1);
+	/* write clk last */
+	if (tck != last_tck)
+		write(tck_fd, tck ? &one : &zero, 1);
+
+	last_tdi = tdi;
+	last_tms = tms;
+	last_tck = tck;
+}
+
+/*
+ * Bitbang interface to manipulate reset lines SRST and TRST
+ *
+ * (1) assert or (0) deassert reset lines
+ */
+static void sysfsgpio_reset(int trst, int srst)
+{
+	const char one[] = "1";
+	const char zero[] = "0";
+
+	/* assume active low */
+	if (srst_fd >= 0)
+		write(srst_fd, srst ? &zero : &one, 1);
+
+	/* assume active low */
+	if (trst_fd >= 0)
+		write(trst_fd, trst ? &zero : &one, 1);
+}
+
+/* No speed control is implemented yet */
+static int sysfsgpio_speed(int speed)
+{
+	return ERROR_OK;
+}
+
+static int sysfsgpio_khz(int khz, int *jtag_speed)
+{
+	/* no adaptive clocking */
+	if (khz == 0)
+		return ERROR_FAIL;
+
+	*jtag_speed = 0;
+	return ERROR_OK;
+}
+
+static int sysfsgpio_speed_div(int speed, int *khz)
+{
+	*khz = 1;
+	return ERROR_OK;
+}
+
+/* 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) {
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], tms_gpio);
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[2], tdi_gpio);
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[3], tdo_gpio);
+	} else if (CMD_ARGC != 0) {
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+
+	command_print(CMD_CTX,
+			"SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdi = %d",
+			tck_gpio, tms_gpio, tdi_gpio, tdo_gpio);
+
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tck)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: tck = %d", tck_gpio);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tms)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tms_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: tms = %d", tms_gpio);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdo)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdo_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: tdo = %d", tdo_gpio);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdi)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdi_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: tdi = %d", tdi_gpio);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_srst)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], srst_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: srst = %d", srst_gpio);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
+{
+	if (CMD_ARGC == 1)
+		COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], trst_gpio);
+
+	command_print(CMD_CTX, "SysfsGPIO num: trst = %d", trst_gpio);
+	return ERROR_OK;
+}
+
+static const struct command_registration sysfsgpio_command_handlers[] = {
+	{
+		.name = "sysfsgpio_jtag_nums",
+		.handler = &sysfsgpio_handle_jtag_gpionums,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio numbers for tck, tms, tdi, tdo. (in that order)",
+		.usage = "(tck tms tdi tdo)* ",
+	},
+	{
+		.name = "sysfsgpio_tck_num",
+		.handler = &sysfsgpio_handle_jtag_gpionum_tck,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for tck.",
+	},
+	{
+		.name = "sysfsgpio_tms_num",
+		.handler = &sysfsgpio_handle_jtag_gpionum_tms,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for tms.",
+	},
+	{
+		.name = "sysfsgpio_tdo_num",
+		.handler = &sysfsgpio_handle_jtag_gpionum_tdo,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for tdo.",
+	},
+	{
+		.name = "sysfsgpio_tdi_num",
+		.handler = &sysfsgpio_handle_jtag_gpionum_tdi,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for tdi.",
+	},
+	{
+		.name = "sysfsgpio_srst_num",
+		.handler = &sysfsgpio_handle_jtag_gpionum_srst,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for srst.",
+	},
+	{
+		.name = "sysfsgpio_trst_num",
+		.handler = &sysfsgpio_handle_jtag_gpionum_trst,
+		.mode = COMMAND_CONFIG,
+		.help = "gpio number for trst.",
+	},
+	COMMAND_REGISTRATION_DONE
+};
+
+static int sysfsgpio_init(void);
+static int sysfsgpio_quit(void);
+
+struct jtag_interface sysfsgpio_interface = {
+	.name = "sysfsgpio",
+	.supported = DEBUG_CAP_TMS_SEQ,
+	.execute_queue = bitbang_execute_queue,
+	.transports = jtag_only,
+	.speed = sysfsgpio_speed,
+	.khz = sysfsgpio_khz,
+	.speed_div = sysfsgpio_speed_div,
+	.commands = sysfsgpio_command_handlers,
+	.init = sysfsgpio_init,
+	.quit = sysfsgpio_quit,
+};
+
+static struct bitbang_interface sysfsgpio_bitbang = {
+	.read = sysfsgpio_read,
+	.write = sysfsgpio_write,
+	.reset = sysfsgpio_reset,
+	.blink = 0
+};
+
+/* helper func to close and cleanup files only if they were valid/ used */
+static void cleanup_fd(int fd, int gpio)
+{
+	if (gpio >= 0) {
+		if (fd >= 0)
+			close(fd);
+
+		unexport_sysfs_gpio(gpio);
+	}
+}
+
+static void cleanup_all_fds(void)
+{
+	cleanup_fd(tck_fd, tck_gpio);
+	cleanup_fd(tms_fd, tms_gpio);
+	cleanup_fd(tdi_fd, tdi_gpio);
+	cleanup_fd(tdo_fd, tdo_gpio);
+	cleanup_fd(trst_fd, trst_gpio);
+	cleanup_fd(srst_fd, srst_gpio);
+}
+
+static int sysfsgpio_init(void)
+{
+	bitbang_interface = &sysfsgpio_bitbang;
+
+	LOG_INFO("SysfsGPIO JTAG bitbang driver");
+
+	if (!(is_gpio_valid(tck_gpio)
+			&& is_gpio_valid(tms_gpio)
+			&& is_gpio_valid(tdi_gpio)
+			&& is_gpio_valid(tdo_gpio))) {
+		if (!is_gpio_valid(tck_gpio))
+			LOG_ERROR("gpio num for tck is invalid");
+		if (!is_gpio_valid(tms_gpio))
+			LOG_ERROR("gpio num for tms is invalid");
+		if (!is_gpio_valid(tdo_gpio))
+			LOG_ERROR("gpio num for tdo is invalid");
+		if (!is_gpio_valid(tdi_gpio))
+			LOG_ERROR("gpio num for tdi is invalid");
+
+		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.
+	 */
+	tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
+	if (tck_fd < 0)
+		goto out_error;
+
+	tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
+	if (tms_fd < 0)
+		goto out_error;
+
+	tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
+	if (tdi_fd < 0)
+		goto out_error;
+
+	tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
+	if (tdo_fd < 0)
+		goto out_error;
+
+	/* assume active low*/
+	trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
+	if (trst_gpio > 0 && trst_fd < 0)
+		goto out_error;
+
+	/* assume active low*/
+	srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
+	if (srst_gpio > 0 && srst_fd < 0)
+		goto out_error;
+
+	return ERROR_OK;
+
+out_error:
+	cleanup_all_fds();
+	return ERROR_JTAG_INIT_FAILED;
+}
+
+static int sysfsgpio_quit(void)
+{
+	cleanup_all_fds();
+	return ERROR_OK;
+}
+
diff --git a/src/jtag/interfaces.c b/src/jtag/interfaces.c
index 4b054be..19d2fcc 100644
--- a/src/jtag/interfaces.c
+++ b/src/jtag/interfaces.c
@@ -113,6 +113,9 @@ extern struct jtag_interface osbdm_interface;
 #if BUILD_OPENDOUS == 1
 extern struct jtag_interface opendous_interface;
 #endif
+#if BUILD_SYSFSGPIO == 1
+extern struct jtag_interface sysfsgpio_interface;
+#endif
 #endif /* standard drivers */
 
 /**
@@ -194,6 +197,9 @@ struct jtag_interface *jtag_interfaces[] = {
 #if BUILD_OPENDOUS == 1
 		&opendous_interface,
 #endif
+#if BUILD_SYSFSGPIO == 1
+		&sysfsgpio_interface,
+#endif
 #endif /* standard drivers */
 		NULL,
 	};