Gary Carlson <gcarlson@carlson-minot.com>:
Fix intermittent J-Link interface startup failures: - Use usb_reset to ensure selected dongle is in known good state. - Assert emulator reset durning status check to prevent supurious failures. - Eliminate status check loop; not needed due to other fixes. git-svn-id: svn://svn.berlios.de/openocd/trunk@2471 b42882b7-edfa-0310-969c-e2dbd0fdcd60
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@ -305,7 +305,6 @@ static int jlink_register_commands(struct command_context_s *cmd_ctx)
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static int jlink_init(void)
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{
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int check_cnt;
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int i;
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jlink_jtag_handle = jlink_usb_open();
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@ -316,23 +315,27 @@ static int jlink_init(void)
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return ERROR_JTAG_INIT_FAILED;
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}
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/*
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* The next three instructions were added after discovering a problem while using an oscilloscope. For the V8
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* SAM-ICE dongle (and likely other j-link device variants), the reset line to the target microprocessor was found to
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* cycle only intermittently during emulator startup (even after encountering the downstream reset instruction later
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* in the code). This was found to create two issues: 1) In general it is a bad practice to not reset a CPU to a known
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* state when starting an emulator and 2) something critical happens inside the dongle when it does the first read
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* following a new USB session. Keeping the processor in reset during the first read collecting version information
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* seems to prevent errant "J-Link command EMU_CMD_VERSION failed" issues.
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*/
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LOG_INFO("J-Link initialization started / target CPU reset initiated");
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jlink_simple_command(EMU_CMD_HW_TRST0);
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jlink_simple_command(EMU_CMD_HW_RESET0);
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sleep(1);
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jlink_hw_jtag_version = 2;
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check_cnt = 0;
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while (check_cnt < 3)
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{
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if (jlink_get_version_info() == ERROR_OK)
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{
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/* attempt to get status */
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jlink_get_status();
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break;
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}
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check_cnt++;
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}
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if (check_cnt == 3)
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{
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LOG_INFO("J-Link initial read failed, don't worry");
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}
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LOG_INFO("J-Link JTAG Interface ready");
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@ -861,6 +864,15 @@ static jlink_jtag_t* jlink_usb_open()
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{
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result->usb_handle = usb_open(dev);
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/*
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* Some j-link dongles experience intermittent communication issues at startup to varying degrees
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* depending on the host operating system. Troubleshooting this problem all the way back to libusb
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* revealed that without a usb reset, the hardware can start in an uncertain state causing a litany
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* of annoying problems. The next step was added to the original code to address this problem.
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*/
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usb_reset(result->usb_handle);
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/* usb_set_configuration required under win32 */
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usb_set_configuration(result->usb_handle, dev->config[0].bConfigurationValue);
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usb_claim_interface(result->usb_handle, 0);
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