tcl: introduce init_target_events and use it for gdb flashing events

This introduces a new global Tcl procedure that is run just after
init_targets and before init_boards.

Its default behaviour is to assign gdb-flash-erase-start and
gdb-flash-write-end to reasonable defaults.

The rationale for doing "reset init" before gdb erases and flashes
memory is that all flash drivers are written in assumption that they
can safely be used only after chip reset (plus chip-specific
configuration in the init handler if any). The need to use "reset
halt" after flashing is because a user expects running firmware after
loading to be the same as running it from power-on-reset.

Change-Id: I9ddc4047611904ca4ca779b73376d2739611948a
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2062
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

doc/openocd.texi

@@ -2109,6 +2109,17 @@ For an example of this scheme see LPC2000 target config files.
 The @code{init_boards} procedure is a similar concept concerning board config files
 (@xref{theinitboardprocedure,,The init_board procedure}.)
 
+@anchor{theinittargeteventsprocedure}
+@subsection The init_target_events procedure
+@cindex init_target_events procedure
+
+A special procedure called @code{init_target_events} is run just after
+@code{init_targets} (@xref{theinittargetsprocedure,,The init_targets
+procedure}.) and before @code{init_board}
+(@xref{theinitboardprocedure,,The init_board procedure}.) It is used
+to set up default target events for the targets that do not have those
+events already assigned.
+
 @subsection ARM Core Specific Hacks
 
 If the chip has a DCC, enable it. If the chip is an ARM9 with some
@@ -4577,13 +4588,14 @@ depending on whether the breakpoint is in RAM or read only memory.
 @item @b{gdb-end}
 @* When the target has halted and GDB is not doing anything (see early halt)
 @item @b{gdb-flash-erase-start}
-@* Before the GDB flash process tries to erase the flash
+@* Before the GDB flash process tries to erase the flash (default is
+@code{reset init})
 @item @b{gdb-flash-erase-end}
 @* After the GDB flash process has finished erasing the flash
 @item @b{gdb-flash-write-start}
 @* Before GDB writes to the flash
 @item @b{gdb-flash-write-end}
-@* After GDB writes to the flash
+@* After GDB writes to the flash (default is @code{reset halt})
 @item @b{gdb-start}
 @* Before the target steps, gdb is trying to start/resume the target
 @item @b{halted}

src/target/startup.tcl

@@ -164,6 +164,21 @@ proc armv4_5 params {
 proc init_targets {} {
 }
 
+proc set_default_target_event {t e s} {
+	if {[$t cget -event $e] == ""} {
+		$t configure -event $e $s
+	}
+}
+
+proc init_target_events {} {
+	set targets [target names]
+
+	foreach t $targets {
+		set_default_target_event $t gdb-flash-erase-start "reset init"
+		set_default_target_event $t gdb-flash-write-end "reset halt"
+	}
+}
+
 # Additionally board config scripts can define a procedure init_board that will be executed after init and init_targets
 proc init_board {} {
 }

src/target/target.c

@@ -1274,6 +1274,10 @@ COMMAND_HANDLER(handle_target_init_command)
 	if (ERROR_OK != retval)
 		return retval;
 
+	retval = command_run_line(CMD_CTX, "init_target_events");
+	if (ERROR_OK != retval)
+		return retval;
+
 	retval = command_run_line(CMD_CTX, "init_board");
 	if (ERROR_OK != retval)
 		return retval;