stlink: Add workaround for intermittent FW info retrieval failure

It appears that on some host USB configurations(2012 MacBook Air)
multiple restarts of openocd tool cause the FW on STLINKv2 dongle to
go into a weird state in which it will no longer respond to
STLINK_GET_VERSION command. This patch adds code that, if said request
fails for the first time, attempts to reset the device and retry to
initialize it and obtain FW information one more time.

Change-Id: I7227fc972adb49d52ae700ad48ab9f66b2aaa72c
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-on: http://openocd.zylin.com/1561
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/jtag/drivers/libusb0_common.h

@@ -47,6 +47,12 @@ static inline int jtag_libusb_claim_interface(jtag_libusb_device_handle *devh,
 	return usb_claim_interface(devh, iface);
 };
 
+static inline int jtag_libusb_release_interface(jtag_libusb_device_handle *devh,
+				       int iface)
+{
+	return usb_release_interface(devh, iface);
+}
+
 int jtag_libusb_open(const uint16_t vids[], const uint16_t pids[],
 		struct jtag_libusb_device_handle **out);
 void jtag_libusb_close(jtag_libusb_device_handle *dev);

src/jtag/drivers/libusb1_common.h

@@ -41,6 +41,12 @@ static inline int jtag_libusb_claim_interface(jtag_libusb_device_handle *devh,
 	return libusb_claim_interface(devh, iface);
 };
 
+static inline int jtag_libusb_release_interface(jtag_libusb_device_handle *devh,
+		int iface)
+{
+	return libusb_release_interface(devh, iface);
+}
+
 int jtag_libusb_open(const uint16_t vids[], const uint16_t pids[],
 		struct jtag_libusb_device_handle **out);
 void jtag_libusb_close(jtag_libusb_device_handle *dev);

src/jtag/drivers/stlink_usb.c

@@ -1447,7 +1447,7 @@ static int stlink_usb_close(void *fd)
 /** */
 static int stlink_usb_open(struct hl_interface_param_s *param, void **fd)
 {
-	int err;
+	int err, retry_count = 1;
 	struct stlink_usb_handle_s *h;
 	enum stlink_jtag_api_version api;
 
@@ -1471,6 +1471,16 @@ static int stlink_usb_open(struct hl_interface_param_s *param, void **fd)
 	LOG_DEBUG("transport: %d vid: 0x%04x pid: 0x%04x", param->transport,
 		param->vid, param->pid);
 
+	/*
+	  On certain host USB configurations(e.g. MacBook Air)
+	  STLINKv2 dongle seems to have its FW in a funky state if,
+	  after plugging it in, you try to use openocd with it more
+	  then once (by launching and closing openocd). In cases like
+	  that initial attempt to read the FW info via
+	  stlink_usb_version will fail and the device has to be reset
+	  in order to become operational.
+	 */
+	do {
 		if (jtag_libusb_open(vids, pids, &h->fd) != ERROR_OK) {
 			LOG_ERROR("open failed");
 			goto error_open;
@@ -1496,11 +1506,35 @@ static int stlink_usb_open(struct hl_interface_param_s *param, void **fd)
 		/* get the device version */
 		err = stlink_usb_version(h);
 
-	if (err != ERROR_OK) {
+		if (err == ERROR_OK) {
+			break;
+		} else if (h->version.stlink == 1 ||
+			   retry_count == 0) {
 			LOG_ERROR("read version failed");
 			goto error_open;
+		} else {
+			err = jtag_libusb_release_interface(h->fd, 0);
+			if (err != ERROR_OK) {
+				LOG_ERROR("release interface failed");
+				goto error_open;
 			}
 
+			err = jtag_libusb_reset_device(h->fd);
+			if (err != ERROR_OK) {
+				LOG_ERROR("reset device failed");
+				goto error_open;
+			}
+
+			jtag_libusb_close(h->fd);
+			/*
+			  Give the device one second to settle down and
+			  reenumerate.
+			 */
+			usleep(1 * 1000 * 1000);
+			retry_count--;
+		}
+	} while (1);
+
 	/* compare usb vid/pid */
 	if ((param->vid != h->vid) || (param->pid != h->pid))
 		LOG_INFO("vid/pid are not identical: 0x%04X/0x%04X 0x%04X/0x%04X",