scripts: runners: nrf: Default to soft reset for the nRF52 series

The Nordic nRF52 series have a peculiarity that is not shared with any
other Nordic families of SoCs: the reset pin can be reconfigured as a
regular GPIO. This has an unintended consequence: if the user has
reconfigured the pin in Devicetree to be a GPIO, `west flash` will
override that and configure the IC to use it as a reset pin, and the
firmware at boot won't be able to switch it back to GPIO, because that
requires a UICR erase. This behavior is very confusing to users, because
the GPIO does not work at all, since it is now just a reset line.

With this patch, `west flash` defaults to using soft reset instead of
pin reset for the nRF52 family of devices, to avoid overwriting the
reset pin configuration that the user includes in the image.

In order to be able to continue to use pin reset for users that so
desire it, a new option `--pinreset` is added that forces the use of pin
reset. The existing `--softreset` option is left exactly as it was, but
it is now applicable only to families other than the nRF52.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

Author: carlescufi

doc/releases/migration-guide-4.1.rst

@@ -50,6 +50,10 @@ Boards
   the required configuration by using ``mikroe_weather_click_i2c`` or ``mikroe_weather_click_spi``
   instead of ``mikroe_weather_click``.
 
+* All nRF52-based boards will now default to soft (system) reset
+  instead of pin reset when flashing with ``west flash``. If you want to keep
+  using pin reset on the nRF52 family of ICs you can use ``west flash --pinreset``.
+
 Devicetree
 **********
 

scripts/west_commands/runners/nrf_common.py

@@ -78,13 +78,14 @@ def _get_suit_starter():
 class NrfBinaryRunner(ZephyrBinaryRunner):
     '''Runner front-end base class for nrf tools.'''
 
-    def __init__(self, cfg, family, softreset, dev_id, erase=False,
+    def __init__(self, cfg, family, softreset, pinreset, dev_id, erase=False,
                  reset=True, tool_opt=None, force=False, recover=False):
         super().__init__(cfg)
         self.hex_ = cfg.hex_file
         # The old --nrf-family options takes upper-case family names
         self.family = family.lower() if family else None
         self.softreset = softreset
+        self.pinreset = pinreset
         self.dev_id = dev_id
         self.erase = bool(erase)
         self.reset = bool(reset)
@@ -117,9 +118,14 @@ def do_add_parser(cls, parser):
                                      'NRF54H', 'NRF91', 'NRF92'],
                             help='''MCU family; still accepted for
                             compatibility only''')
+        # Not using a mutual exclusive group for softreset and pinreset due to
+        # the way dump_runner_option_help() works in run_common.py
         parser.add_argument('--softreset', required=False,
                             action='store_true',
-                            help='use reset instead of pinreset')
+                            help='use softreset instead of pinreset')
+        parser.add_argument('--pinreset', required=False,
+                            action='store_true',
+                            help='use pinreset instead of softreset')
         parser.add_argument('--snr', required=False, dest='dev_id',
                             help='obsolete synonym for -i/--dev-id')
         parser.add_argument('--force', required=False,
@@ -412,13 +418,18 @@ def program_hex(self):
 
 
     def reset_target(self):
-        if self.family == 'nrf52' and not self.softreset:
+        # Default to soft reset on nRF52 only, because ICs in these series can
+        # reconfigure the reset pin as a regular GPIO
+        default = "RESET_SYSTEM" if self.family == 'nrf52' else "RESET_PIN"
+        kind = ("RESET_SYSTEM" if self.softreset else "RESET_PIN" if
+               self.pinreset else default)
+
+        if self.family == 'nrf52' and kind == "RESET_PIN":
+            # Write to the UICR enabling nRESET in the corresponding pin
             self.exec_op('pinreset-enable')
 
-        if self.softreset:
-            self.exec_op('reset', kind="RESET_SYSTEM")
-        else:
-            self.exec_op('reset', kind="RESET_PIN")
+        self.logger.debug(f'Reset kind: {kind}')
+        self.exec_op('reset', kind=kind)
 
     @abc.abstractmethod
     def do_require(self):
@@ -488,6 +499,10 @@ def flush_ops(self, force=True):
     def do_run(self, command, **kwargs):
         self.do_require()
 
+        if self.softreset and self.pinreset:
+            raise RuntimeError('Options --softreset and --pinreset are mutually '
+                               'exclusive.')
+
         self.ensure_output('hex')
         if IntelHex is None:
             raise RuntimeError('Python dependency intelhex was missing; '

scripts/west_commands/runners/nrfjprog.py

@@ -17,11 +17,11 @@
 class NrfJprogBinaryRunner(NrfBinaryRunner):
     '''Runner front-end for nrfjprog.'''
 
-    def __init__(self, cfg, family, softreset, dev_id, erase=False,
+    def __init__(self, cfg, family, softreset, pinreset, dev_id, erase=False,
                  reset=True, tool_opt=None, force=False, recover=False,
                  qspi_ini=None):
 
-        super().__init__(cfg, family, softreset, dev_id, erase, reset,
+        super().__init__(cfg, family, softreset, pinreset, dev_id, erase, reset,
                          tool_opt, force, recover)
 
         self.qspi_ini = qspi_ini
@@ -37,7 +37,7 @@ def tool_opt_help(cls) -> str:
     @classmethod
     def do_create(cls, cfg, args):
         return NrfJprogBinaryRunner(cfg, args.nrf_family, args.softreset,
-                                    args.dev_id, erase=args.erase,
+                                    args.pinreset, args.dev_id, erase=args.erase,
                                     reset=args.reset,
                                     tool_opt=args.tool_opt, force=args.force,
                                     recover=args.recover, qspi_ini=args.qspi_ini)

scripts/west_commands/runners/nrfutil.py

@@ -16,11 +16,11 @@
 class NrfUtilBinaryRunner(NrfBinaryRunner):
     '''Runner front-end for nrfutil.'''
 
-    def __init__(self, cfg, family, softreset, dev_id, erase=False,
+    def __init__(self, cfg, family, softreset, pinreset, dev_id, erase=False,
                  reset=True, tool_opt=None, force=False, recover=False,
                  suit_starter=False):
 
-        super().__init__(cfg, family, softreset, dev_id, erase, reset,
+        super().__init__(cfg, family, softreset, pinreset, dev_id, erase, reset,
                          tool_opt, force, recover)
 
         self.suit_starter = suit_starter
@@ -39,7 +39,7 @@ def tool_opt_help(cls) -> str:
     @classmethod
     def do_create(cls, cfg, args):
         return NrfUtilBinaryRunner(cfg, args.nrf_family, args.softreset,
-                                   args.dev_id, erase=args.erase,
+                                   args.pinreset, args.dev_id, erase=args.erase,
                                    reset=args.reset,
                                    tool_opt=args.tool_opt, force=args.force,
                                    recover=args.recover,