examination of the instruction and data bus activity. Trace
activity is controlled through an ``Embedded Trace Module'' (ETM)
on one of the core's scan chains. The ETM emits voluminous data
-through a ``trace port''. The trace port is accessed in one
-of two ways. When its signals are pinned out from the chip,
-boards may provide a special high speed debugging connector;
-software support for this is not configured by default, use
-the ``--enable-oocd_trace'' option. Alternatively, trace data
-may be stored an on-chip SRAM which is packaged as an ``Embedded
-Trace Buffer'' (ETB). An ETB has its own TAP, usually right after
-its associated ARM core. OpenOCD supports the ETM, and your
-target configuration should set it up with the relevant trace
-port: ``etb'' for chips which use that, else the board-specific
-option will be either ``oocd_trace'' or ``dummy''.
+through a ``trace port''. (@xref{ARM Tracing}.)
+If you are using an external trace port,
+configure it in your board config file.
+If you are using an on-chip ``Embedded Trace Buffer'' (ETB),
+configure it in your target config file.
@example
etm config $_TARGETNAME 16 normal full etb
Some of those operations don't fit well in that framework, so they are
exposed here using architecture or implementation specific commands.
+@anchor{ARM Tracing}
+@subsection ARM Tracing
+@cindex ETM
+@cindex ETB
+
+CPUs based on ARM cores may include standard tracing interfaces,
+based on an ``Embedded Trace Module'' (ETM) which sends voluminous
+address and data bus trace records to a ``Trace Port''.
+
+@itemize
+@item
+Development-oriented boards will sometimes provide a high speed
+trace connector for collecting that data, when the particular CPU
+supports such an interface.
+(The standard connector is a 38-pin Mictor, with both JTAG
+and trace port support.)
+Those trace connectors are supported by higher end JTAG adapters
+and some logic analyzer modules; frequently those modules can
+buffer several megabytes of trace data.
+Configuring an ETM coupled to such an external trace port belongs
+in the board-specific configuration file.
+@item
+If the CPU doesn't provide an external interface, it probably
+has an ``Embedded Trace Buffer'' (ETB) on the chip, which is a
+dedicated SRAM. 4KBytes is one common ETB size.
+Configuring an ETM coupled only to an ETB belongs in the CPU-specific
+(target) configuration file, since it works the same on all boards.
+@end itemize
+
+ETM support in OpenOCD doesn't seem to be widely used yet.
+
+@quotation Issues
+ETM support may be buggy, and at least some @command{etm config}
+parameters should be detected by asking the ETM for them.
+It seems like a GDB hookup should be possible,
+as well as triggering trace on specific events
+(perhaps @emph{handling IRQ 23} or @emph{calls foo()}).
+There should be GUI tools to manipulate saved trace data and help
+analyse it in conjunction with the source code.
+It's unclear how much of a common interface is shared
+with the current XScale trace support, or should be
+shared with eventual Nexus-style trace module support.
+@end quotation
+
+@subsubsection ETM Configuration
+ETM setup is coupled with the trace port driver configuration.
+
+@deffn {Config Command} {etm config} target width mode clocking driver
+Declares the ETM associated with @var{target}, and associates it
+with a given trace port @var{driver}. @xref{Trace Port Drivers}.
+
+Several of the parameters must reflect the trace port configuration.
+The @var{width} must be either 4, 8, or 16.
+The @var{mode} must be @option{normal}, @option{multiplexted},
+or @option{demultiplexted}.
+The @var{clocking} must be @option{half} or @option{full}.
+
+@quotation Note
+You can see the ETM registers using the @command{reg} command, although
+not all of those possible registers are present in every ETM.
+@end quotation
+@end deffn
+
+@deffn Command {etm info}
+Displays information about the current target's ETM.
+@end deffn
+
+@deffn Command {etm status}
+Displays status of the current target's ETM:
+is the ETM idle, or is it collecting data?
+Did trace data overflow?
+Was it triggered?
+@end deffn
+
+@deffn Command {etm tracemode} [type context_id_bits cycle_accurate branch_output]
+Displays what data that ETM will collect.
+If arguments are provided, first configures that data.
+When the configuration changes, tracing is stopped
+and any buffered trace data is invalidated.
+
+@itemize
+@item @var{type} ... one of
+@option{none} (save nothing),
+@option{data} (save data),
+@option{address} (save addresses),
+@option{all} (save data and addresses)
+@item @var{context_id_bits} ... 0, 8, 16, or 32
+@item @var{cycle_accurate} ... @option{enable} or @option{disable}
+@item @var{branch_output} ... @option{enable} or @option{disable}
+@end itemize
+@end deffn
+
+@deffn Command {etm trigger_percent} percent
+@emph{Buggy and effectively a NOP ... @var{percent} from 2..100}
+@end deffn
+
+@subsubsection ETM Trace Operation
+
+After setting up the ETM, you can use it to collect data.
+That data can be exported to files for later analysis.
+It can also be parsed with OpenOCD, for basic sanity checking.
+
+@deffn Command {etm analyze}
+Reads trace data into memory, if it wasn't already present.
+Decodes and prints the data that was collected.
+@end deffn
+
+@deffn Command {etm dump} filename
+Stores the captured trace data in @file{filename}.
+@end deffn
+
+@deffn Command {etm image} filename [base_address] [type]
+Opens an image file.
+@end deffn
+
+@deffn Command {etm load} filename
+Loads captured trace data from @file{filename}.
+@end deffn
+
+@deffn Command {etm start}
+Starts trace data collection.
+@end deffn
+
+@deffn Command {etm stop}
+Stops trace data collection.
+@end deffn
+
+@anchor{Trace Port Drivers}
+@subsubsection Trace Port Drivers
+
+To use an ETM trace port it must be associated with a driver.
+
+@deffn {Trace Port Driver} etb
+Use the @option{etb} driver if you are configuring an ETM
+to use on-chip ETB memory.
+@deffn {Config Command} {etb config} target etb_tap
+Associates the ETM for @var{target} with the ETB at @var{etb_tap}.
+You can see the ETB registers using the @command{reg} command.
+@end deffn
+@end deffn
+
+@deffn {Trace Port Driver} etm_dummy
+Use the @option{etm_dummy} driver if you are configuring an ETM that's
+not connected to anything (on-chip ETB or off-chip trace connector).
+@emph{This driver lets OpenOCD talk to the ETM, but it does not expose
+any trace data collection.}
+@deffn {Config Command} {etm_dummy config} target
+Associates the ETM for @var{target} with a dummy driver.
+@end deffn
+@end deffn
+
+@deffn {Trace Port Driver} oocd_trace
+This driver isn't available unless OpenOCD was explicitly configured
+with the @option{--enable-oocd_trace} option. You probably don't want
+to configure it unless you've built the appropriate prototype hardware;
+it's @emph{proof-of-concept} software.
+
+Use the @option{oocd_trace} driver if you are configuring an ETM that's
+connected to an off-chip trace connector.
+
+@deffn {Config Command} {oocd_trace config} target tty
+Associates the ETM for @var{target} with a trace driver which
+collects data through the serial port @var{tty}.
+@end deffn
+
+@deffn Command {oocd_trace resync}
+Re-synchronizes with the capture clock.
+@end deffn
+
+@deffn Command {oocd_trace status}
+Reports whether the capture clock is locked or not.
+@end deffn
+@end deffn
+
+
@subsection ARMv4 and ARMv5 Architecture
@cindex ARMv4 specific commands
@cindex ARMv5 specific commands
{
etm_cmd = register_command(cmd_ctx, NULL, "etm", NULL, COMMAND_ANY, "Embedded Trace Macrocell");
- register_command(cmd_ctx, etm_cmd, "config", handle_etm_config_command, COMMAND_CONFIG, "etm config <target> <port_width> <port_mode> <clocking> <capture_driver>");
+ register_command(cmd_ctx, etm_cmd, "config", handle_etm_config_command,
+ COMMAND_CONFIG, "etm config <target> <port_width> <port_mode> <clocking> <capture_driver>");
return ERROR_OK;
}
int etm_register_user_commands(struct command_context_s *cmd_ctx)
{
register_command(cmd_ctx, etm_cmd, "tracemode", handle_etm_tracemode_command,
- COMMAND_EXEC, "configure trace mode <none|data|address|all> <context id bits> <cycle accurate> <branch output");
+ COMMAND_EXEC, "configure trace mode <none|data|address|all> "
+ "<context_id_bits> <cycle_accurate> <branch_output>");
register_command(cmd_ctx, etm_cmd, "info", handle_etm_info_command,
COMMAND_EXEC, "display info about the current target's ETM");
- register_command(cmd_ctx, etm_cmd, "trigger_percent <percent>", handle_etm_trigger_percent_command,
+ register_command(cmd_ctx, etm_cmd, "trigger_percent", handle_etm_trigger_percent_command,
COMMAND_EXEC, "amount (<percent>) of trace buffer to be filled after the trigger occured");
register_command(cmd_ctx, etm_cmd, "status", handle_etm_status_command,
COMMAND_EXEC, "display current target's ETM status");
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