instrument/daq: Add an explicit time column to the DAQ measurements

Add the monotonic clock time to the energy measurements to help
correlate the measurement with those of other collectors, like
FtraceCollector or LogcatCollector.

devlib/instrument/daq.py

@@ -16,8 +16,10 @@
 import os
 import shutil
 import tempfile
+import time
 from itertools import chain, zip_longest
 
+from devlib.host import PACKAGE_BIN_DIRECTORY
 from devlib.instrument import Instrument, MeasurementsCsv, CONTINUOUS
 from devlib.exception import HostError
 from devlib.utils.csvutil import csvwriter, create_reader
@@ -45,7 +47,8 @@ class DaqInstrument(Instrument):
                  dv_range=0.2,
                  sample_rate_hz=10000,
                  channel_map=(0, 1, 2, 3, 4, 5, 6, 7, 16, 17, 18, 19, 20, 21, 22, 23),
-                 keep_raw=False
+                 keep_raw=False,
+                 time_as_clock_monotonic=True
                  ):
         # pylint: disable=no-member
         super(DaqInstrument, self).__init__(target)
@@ -53,6 +56,7 @@ class DaqInstrument(Instrument):
         self._need_reset = True
         self._raw_files = []
         self.tempdir = None
+        self.target_monotonic_clock_at_start = 0.0
         if DaqClient is None:
             raise HostError('Could not import "daqpower": {}'.format(import_error_mesg))
         if labels is None:
@@ -76,11 +80,30 @@ class DaqInstrument(Instrument):
                                                  channel_map=channel_map,
                                                  labels=labels)
         self.sample_rate_hz = sample_rate_hz
+        self.time_as_clock_monotonic = time_as_clock_monotonic
 
+        self.add_channel('Time', 'time')
         for label in labels:
             for kind in ['power', 'voltage']:
                 self.add_channel(label, kind)
 
+        if time_as_clock_monotonic:
+            host_path = os.path.join(PACKAGE_BIN_DIRECTORY, self.target.abi,
+                                     'get_clock_monotonic')
+            self.clock_monotonic_cmd = self.target.install_if_needed(host_path,
+                                                                     search_system_binaries=False)
+
+    def calculate_monotonic_offset(self):
+        time_before = time.time()
+        out = self.target.execute(self.clock_monotonic_cmd)
+        time_after = time.time()
+
+        remote_clock_monotonic = float(out)
+        propagation_delay = (time_after - time_before) / 2
+        monotonic_at_end = remote_clock_monotonic + propagation_delay
+
+        return time_after - monotonic_at_end
+
     def reset(self, sites=None, kinds=None, channels=None):
         super(DaqInstrument, self).reset(sites, kinds, channels)
         self.daq_client.close()
@@ -90,9 +113,19 @@ class DaqInstrument(Instrument):
 
     def start(self):
         if self._need_reset:
-            self.reset()
+            # Preserve channel order
+            self.reset(channels=self.channels.keys())
+
+        if self.time_as_clock_monotonic:
+            target_monotonic_offset = self.calculate_monotonic_offset()
+            time_start = time.time()
+
         self.daq_client.start()
 
+        if self.time_as_clock_monotonic:
+            time_end = time.time()
+            self.target_monotonic_clock_at_start = (time_start + time_end) / 2 - target_monotonic_offset
+
     def stop(self):
         self.daq_client.stop()
         self._need_reset = True
@@ -118,11 +151,12 @@ class DaqInstrument(Instrument):
                     site_readers[site] = reader
                     file_handles.append(fh)
                 except KeyError:
+                    if not site.startswith("Time"):
                         message = 'Could not get DAQ trace for {}; Obtained traces are in {}'
                         raise HostError(message.format(site, self.tempdir))
 
             # The first row is the headers
-            channel_order = []
+            channel_order = ['Time_time']
             for site, reader in site_readers.items():
                 channel_order.extend(['{}_{}'.format(site, kind)
                                       for kind in next(reader)])
@@ -131,7 +165,11 @@ class DaqInstrument(Instrument):
                 row_iter = zip_longest(*site_readers.values(), fillvalue=(None, None))
                 for raw_row in row_iter:
                     raw_row = list(chain.from_iterable(raw_row))
+                    raw_row.insert(0, _read_rows.row_time_s)
                     yield raw_row
+                    _read_rows.row_time_s += 1.0 / self.sample_rate_hz
+
+            _read_rows.row_time_s = self.target_monotonic_clock_at_start
 
             with csvwriter(outfile) as writer:
                 field_names = [c.label for c in self.active_channels]

src/get_clock_monotonic/Makefile

@@ -0,0 +1,6 @@
+CFLAGS=-Wall --pedantic-errors -O2 -static
+
+all: get_clock_monotonic
+
+get_clock_monotonic: get_clock_monotonic.c
+	$(CC) $(CFLAGS) $^ -o $@

src/get_clock_monotonic/get_clock_monotonic.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+int main(void) {
+    int ret;
+    struct timespec tp;
+
+    ret = clock_gettime(CLOCK_MONOTONIC, &tp);
+    if (ret) {
+        perror("clock_gettime()");
+        return EXIT_FAILURE;
+    }
+
+    printf("%ld.%ld\n", tp.tv_sec, tp.tv_nsec);
+
+    return EXIT_SUCCESS;
+}