diff options
author | Andreas Fritiofson <andreas.fritiofson@gmail.com> | 2014-03-07 20:08:31 +0100 |
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committer | Andreas Fritiofson <andreas.fritiofson@gmail.com> | 2014-03-07 21:19:12 +0000 |
commit | 17fddb4289cb632a414d9780b3c2e60e368fa083 (patch) | |
tree | 2c37b0b8dc765482c9bec0cce714208f049f7f38 /src/jtag/drivers/stlink_usb.c | |
parent | d82490adfbb63716361b1867e7359b656de76ac6 (diff) |
stlink: Use callback to increase frequency of trace data sampling
The ST-LINK/V2 has limited internal buffering, such that trace data
can be missed if the target is generating data at a rate quicker than
the OpenOCD trace sampling. The issue of lost data is compounded since
individual TPIU packets may be split across individual STLINK_TRACE_EP
reads, and misleading results can occur if mid-packet loss occurs.
This patch increases the frequency of checking for pending trace data
with the aim of minimising such losses. Note: With the limited (I/O
and memory) bandwidth of the ST-LINK/V2 there cannot, however, be a
guarantee against trace data loss.
The timer callback is only added when enabling tracing, and is removed
when tracing is disabled.
Change-Id: Ibde9794b77793d3068f88cb5c1a26f9ceadcbd8a
Signed-off-by: James G. Smith <jsmith@ecoscentric.com>
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/1661
Tested-by: jenkins
Diffstat (limited to 'src/jtag/drivers/stlink_usb.c')
-rw-r--r-- | src/jtag/drivers/stlink_usb.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/src/jtag/drivers/stlink_usb.c b/src/jtag/drivers/stlink_usb.c index e9d13d56..06ec4b70 100644 --- a/src/jtag/drivers/stlink_usb.c +++ b/src/jtag/drivers/stlink_usb.c @@ -830,6 +830,12 @@ static void stlink_usb_trace_read(void *handle) } } +static int stlink_usb_trace_read_callback(void *handle) +{ + stlink_usb_trace_read(handle); + return ERROR_OK; +} + static enum target_state stlink_usb_v2_get_status(void *handle) { int result; @@ -1006,8 +1012,10 @@ static void stlink_usb_trace_disable(void *handle) h->cmdbuf[h->cmdidx++] = STLINK_DEBUG_APIV2_STOP_TRACE_RX; res = stlink_usb_xfer(handle, h->databuf, 2); - if (res == ERROR_OK) + if (res == ERROR_OK) { h->trace.enabled = false; + target_unregister_timer_callback(stlink_usb_trace_read_callback, handle); + } } @@ -1044,6 +1052,14 @@ static int stlink_usb_trace_enable(void *handle) if (res == ERROR_OK) { h->trace.enabled = true; LOG_DEBUG("Tracing: recording at %" PRIu32 "Hz\n", trace_hz); + /* We need the trace read function to be called at a + * high-enough frequency to ensure reasonable + * "timeliness" in processing ITM/DWT data. + * TODO: An alternative could be using the asynchronous + * features of the libusb-1.0 API to queue up one or more + * reads in advance and requeue them once they are + * completed. */ + target_register_timer_callback(stlink_usb_trace_read_callback, 1, 1, handle); } } else { LOG_ERROR("Tracing is not supported by this version."); @@ -1065,7 +1081,7 @@ static int stlink_usb_run(void *handle) res = stlink_usb_write_debug_reg(handle, DCB_DHCSR, DBGKEY|C_DEBUGEN); /* Try to start tracing, if requested */ - if (res == ERROR_OK && h->trace.source_hz) { + if (res == ERROR_OK && h->trace.source_hz && !h->trace.enabled) { if (stlink_usb_trace_enable(handle) == ERROR_OK) LOG_DEBUG("Tracing: enabled\n"); else |