mpm: Change SW/HW compat check to use last_rev_compat

Newer revisions of the E320 and N3xx motherboards use EEPROM version 3,
and store a rev_compat field. The rev_compat is the last revision that
this hardware is compatible with. We now use that instead of simply the
revision.

4 files changed, 33 insertions, 18 deletions

diff --git a/mpm/python/usrp_mpm/bist.py b/mpm/python/usrp_mpm/bist.py
index e26d6d36c..7957f2f37 100644
--- a/mpm/python/usrp_mpm/bist.py
+++ b/mpm/python/usrp_mpm/bist.py
@@ -495,7 +495,7 @@ class UsrpBIST(object):
         # If this is true, trigger a reload of the default FPGA image
         self.reload_fpga_image = False
         try:
-            default_rev = self.get_mb_periph_mgr().mboard_max_rev
+            default_rev = self.get_mb_periph_mgr().mboard_last_rev_compat
         except ImportError:
             # This means we're in dry run mode or something like that, so just
             # pick something
diff --git a/mpm/python/usrp_mpm/periph_manager/base.py b/mpm/python/usrp_mpm/periph_manager/base.py
index e297effbd..a3adc56c8 100644
--- a/mpm/python/usrp_mpm/periph_manager/base.py
+++ b/mpm/python/usrp_mpm/periph_manager/base.py
@@ -85,7 +85,7 @@ class PeriphManagerBase(object):
     # For checking revision numbers, this is the highest revision that this
     # particular version of MPM supports. Leave at None to skip a max rev
     # check.
-    mboard_max_rev = None
+    mboard_last_rev_compat = None
     # A list of available sensors on the motherboard. This dictionary is a map
     # of the form sensor_name -> method name
     mboard_sensor_callback_map = {}
@@ -287,22 +287,37 @@ class PeriphManagerBase(object):
                     )
                 )
                 raise RuntimeError("Invalid PID found in EEPROM.")
-        if 'rev' in eeprom_head:
-            try:
-                rev_numeric = int(eeprom_head.get('rev'))
-            except (ValueError, TypeError):
+        # The rev_compat is either directly stored in the EEPROM, or we fall
+        # back first to the dt_compat, then the rev itself (because every rev is
+        # compatible with itself).
+        # The dt_compat solution is a technically a hack, but it works because
+        # all hardware we have released until we made this change happened to
+        # have a dt_compat that also works as a rev_compat.
+        rev_compat = \
+            eeprom_head.get('rev_compat',
+                            eeprom_head.get('dt_compat',
+                                            eeprom_head.get('rev')))
+        try:
+            rev_compat = int(rev_compat)
+        except (ValueError, TypeError):
+            raise RuntimeError(
+                "Invalid revision compat info read from EEPROM!"
+            )
+        # We check if this software is actually compatible with the hardware.
+        # In order for the software to be able to understand the hardware, the
+        # rev_compat value (stored on the EEPROM) must be smaller or equal to
+        # the value stored in the software itself.
+        if self.mboard_last_rev_compat is None:
+            self.log.warning("Skipping HW/SW compatibility check!")
+        else:
+            if rev_compat > self.mboard_last_rev_compat:
                 raise RuntimeError(
-                    "Invalid revision info read from EEPROM!"
+                    "Software is maximally compatible with revision `{}', but "
+                    "the hardware has revision `{}' and is minimally compatible "
+                    "with hardware revision `{}'. Please upgrade your version of"
+                    "MPM in order to use this device."
+                    .format(self.mboard_last_rev_compat, mboard_info['rev'], rev_compat)
                 )
-            if self.mboard_max_rev is not None \
-                    and rev_numeric > self.mboard_max_rev:
-                raise RuntimeError(
-                    "Device has revision `{}', but max supported " \
-                    "revision is `{}'".format(
-                        rev_numeric, self.mboard_max_rev
-                    ))
-        else:
-            raise RuntimeError("No revision found in EEPROM.")
         return mboard_info
 
     def _get_dboard_eeprom_info(self):
diff --git a/mpm/python/usrp_mpm/periph_manager/e320.py b/mpm/python/usrp_mpm/periph_manager/e320.py
index 96a184477..3135a6994 100644
--- a/mpm/python/usrp_mpm/periph_manager/e320.py
+++ b/mpm/python/usrp_mpm/periph_manager/e320.py
@@ -78,7 +78,7 @@ class e320(ZynqComponents, PeriphManagerBase):
     mboard_info = {"type": "e3xx",
                    "product": "e320"
                   }
-    mboard_max_rev = 4  # Rev E
+    mboard_last_rev_compat = 0
     mboard_sensor_callback_map = {
         'ref_locked': 'get_ref_lock_sensor',
         'gps_locked': 'get_gps_lock_sensor',
diff --git a/mpm/python/usrp_mpm/periph_manager/n3xx.py b/mpm/python/usrp_mpm/periph_manager/n3xx.py
index 5856036e3..0a2801f44 100644
--- a/mpm/python/usrp_mpm/periph_manager/n3xx.py
+++ b/mpm/python/usrp_mpm/periph_manager/n3xx.py
@@ -131,7 +131,7 @@ class n3xx(ZynqComponents, PeriphManagerBase):
     mboard_eeprom_offset = 0
     mboard_eeprom_max_len = 256
     mboard_info = {"type": "n3xx"}
-    mboard_max_rev = 7 # 7 == RevH
+    mboard_last_rev_compat = 5 # last known compat through dt_compat field
     mboard_sensor_callback_map = {
         'ref_locked': 'get_ref_lock_sensor',
         'gps_locked': 'get_gps_lock_sensor',