From 10d00940e509d4b0f5dfa170b94acc719c026dd0 Mon Sep 17 00:00:00 2001
From: Douglas Raillard <douglas.raillard@arm.com>
Date: Tue, 26 Jul 2022 16:58:31 +0100
Subject: [PATCH] lisa.energy_model: Use LISA kernel module fallback

FEATURE

If the energy model is not exposed on the target in sysfs, load the lisa
kernel module with the right feature enabled and retry. This feature
will expose the EM as a folder hierarchy using in-kernel APIs
---
 lisa/energy_model.py | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/lisa/energy_model.py b/lisa/energy_model.py
index 810d32ac4..b3bd2405c 100644
--- a/lisa/energy_model.py
+++ b/lisa/energy_model.py
@@ -20,6 +20,7 @@ from collections import namedtuple, OrderedDict
 from itertools import product
 import operator
 import re
+from contextlib import nullcontext
 
 import pandas
 
@@ -29,7 +30,7 @@ from devlib.exception import TargetStableError
 from lisa.utils import Loggable, Serializable, memoized, groupby, get_subclasses, deprecate, grouper
 from lisa.datautils import df_deduplicate
 from lisa.analysis.frequency import FrequencyAnalysis
-
+from lisa._kmod import LISAFtraceDynamicKmod
 
 
 def _read_multiple_oneline_files(target, glob_patterns):
@@ -281,6 +282,11 @@ class PowerDomain(_CpuTree):
         self.idle_states = idle_states
 
 
+class EnergyModelNotFoundError(TargetStableError):
+    def __init__(self):
+        super().__init__('Unable to probe for energy model on target.')
+
+
 class EnergyModel(Serializable, Loggable):
     """Represents hierarchical CPU topology with power and capacity data
 
@@ -770,7 +776,7 @@ class EnergyModel(Serializable, Loggable):
         """
         try:
             cls._find_subcls(target)
-        except TargetStableError:
+        except EnergyModelNotFoundError:
             return False
         else:
             return True
@@ -786,7 +792,7 @@ class EnergyModel(Serializable, Loggable):
             if subcls.probe_target(target):
                 return subcls
 
-        raise TargetStableError('Unable to probe for energy model on target.')
+        raise EnergyModelNotFoundError()
 
     @classmethod
     def from_target(cls, target):
@@ -803,9 +809,24 @@ class EnergyModel(Serializable, Loggable):
         """
         logger = cls.get_logger('from_target')
 
-        subcls = cls._find_subcls(target)
-        logger.info(f'Attempting to load EM using {subcls.__name__}')
-        em = subcls.from_target(target)
+        try:
+            subcls = cls._find_subcls(target)
+        except EnergyModelNotFoundError:
+            # If we could not find a suitable EM description in sysfs, load the
+            # LISA kernel module with the feature that will expose the EM as a
+            # directory tree and retry.
+            @contextmanager
+            def _cm():
+                kmod = target.get_kmod(LISAFtraceDynamicKmod)
+                with kmod.run(kmod_params={'features': ['em_sysfs']}):
+                    yield cls._find_subcls(target)
+            cm = _cm()
+        else:
+            cm = nullcontext(subcls)
+
+        with cm as subcls:
+            logger.info(f'Attempting to load EM using {subcls.__name__}')
+            em = subcls.from_target(target)
 
         cpu_missing_idle_states = sorted(
             node.cpu
-- 
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