new "stellaris recover" command

Stellaris chips have a procedure for restoring the chip to
what's effectively the "as-manufactured" state, with all the
non-volatile memory erased.  That includes all flash memory,
plus things like the flash protection bits and various control
words which can for example disable debugger access.  clearly,
this can be useful during development.

Luminary/TI provides an MS-Windows utility to perform this
procedure along with its Stellaris developer kits.  Now OpenOCD
users will no longer need to use that MS-Windows utility.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

NEWS

@@ -10,6 +10,12 @@ Boundary Scan:
 Target Layer:
 
 Flash Layer:
+	New "stellaris recover" command, implements the procedure
+		to recover locked devices (restoring non-volatile
+		state to the factory defaults, including erasing
+		the flash and its protection bits, and possibly
+		re-enabling hardware debugging).
+
 
 Board, Target, and Interface Configuration Scripts:
 

doc/openocd.texi

@@ -4497,6 +4497,21 @@ flash bank stellaris 0 0 0 0 $_TARGETNAME
 @end example
 @end deffn
 
+@deffn Command {stellaris recover bank_id}
+Performs the @emph{Recovering a "Locked" Device} procedure to
+restore the flash specified by @var{bank_id} and its associated
+nonvolatile registers to their factory default values (erased).
+This is the only way to remove flash protection or re-enable
+debugging if that capability has been disabled.
+
+Note that the final "power cycle the chip" step in this procedure
+must be performed by hand, since OpenOCD can't do it.
+@quotation Warning
+if more than one Stellaris chip is connected, the procedure is
+applied to all of them.
+@end quotation
+@end deffn
+
 @deffn {Flash Driver} stm32x
 All members of the STM32 microcontroller family from ST Microelectronics
 include internal flash and use ARM Cortex M3 cores.

src/flash/nor/stellaris.c

@@ -1170,13 +1170,79 @@ COMMAND_HANDLER(stellaris_handle_mass_erase_command)
 	return ERROR_OK;
 }
 
+/**
+ * Perform the Stellaris "Recovering a 'Locked' Device procedure.
+ * This performs a mass erase and then restores all nonvolatile registers
+ * (including USER_* registers and flash lock bits) to their defaults.
+ * Accordingly, flash can be reprogrammed, and JTAG can be used.
+ *
+ * NOTE that DustDevil parts (at least rev A0 silicon) have errata which
+ * can affect this operation if flash protection has been enabled.
+ */
+COMMAND_HANDLER(stellaris_handle_recover_command)
+{
+	struct flash_bank *bank;
+	int retval;
+
+	retval = CALL_COMMAND_HANDLER(flash_command_get_bank, 0, &bank);
+	if (retval != ERROR_OK)
+		return retval;
+
+	/* REVISIT ... it may be worth sanity checking that the AP is
+	 * inactive before we start.  ARM documents that switching a DP's
+	 * mode while it's active can cause fault modes that need a power
+	 * cycle to recover.
+	 */
+
+	/* assert SRST */
+	if (!(jtag_get_reset_config() & RESET_HAS_SRST)) {
+		LOG_ERROR("Can't recover Stellaris flash without SRST");
+		return ERROR_FAIL;
+	}
+	jtag_add_reset(0, 1);
+
+	for (int i = 0; i < 5; i++) {
+		retval = dap_to_swd(bank->target);
+		if (retval != ERROR_OK)
+			goto done;
+
+		retval = dap_to_jtag(bank->target);
+		if (retval != ERROR_OK)
+			goto done;
+	}
+
+	/* de-assert SRST */
+	jtag_add_reset(0, 0);
+	retval = jtag_execute_queue();
+
+	/* wait 400+ msec ... OK, "1+ second" is simpler */
+	sleep(1);
+
+	/* USER INTERVENTION required for the power cycle
+	 * Restarting OpenOCD is likely needed because of mode switching.
+	 */
+	LOG_INFO("USER ACTION:  "
+		"power cycle Stellaris chip, then restart OpenOCD.");
+
+done:
+	return retval;
+}
+
 static const struct command_registration stellaris_exec_command_handlers[] = {
 	{
 		.name = "mass_erase",
 		.handler = stellaris_handle_mass_erase_command,
 		.mode = COMMAND_EXEC,
+		.usage = "bank_id",
 		.help = "erase entire device",
 	},
+	{
+		.name = "recover",
+		.handler = stellaris_handle_recover_command,
+		.mode = COMMAND_EXEC,
+		.usage = "bank_id",
+		.help = "recover locked device",
+	},
 	COMMAND_REGISTRATION_DONE
 };
 static const struct command_registration stellaris_command_handlers[] = {