libtimeinstate: add getCpuFreqs() function

Currently the KernelCpuUidFreqTimeReader reads the first line of
/proc/uid_time_in_state to determine a device's available CPU
frequencies, but libtimeinstate already reads this information from
sysfs files that are supported upstream. Add a function to provide
this information to libtimeinstate's users & eliminate the need to
read the proc file for this data.
Add a sanity check in libtimeinstate_test to confirm that
getCpuFreqs() and getUidCpuFreqTimes() report the same number of
frequencies for each cluster.

Bug: 138317993
Test: libtimeinstate_test passes
Change-Id: I3e8c632d14bbeb552d7e52bd83a9b4a64dec408d
Signed-off-by: Connor O'Brien <connoro@google.com>

3 files changed, 17 insertions, 0 deletions

diff --git a/libs/cputimeinstate/cputimeinstate.cpp b/libs/cputimeinstate/cputimeinstate.cpp
index 7b7a7e370e..037846b4a4 100644
--- a/libs/cputimeinstate/cputimeinstate.cpp
+++ b/libs/cputimeinstate/cputimeinstate.cpp
@@ -213,6 +213,11 @@ bool startTrackingUidTimes() {
             attachTracepointProgram("power", "cpu_frequency");
 }
 
+std::optional<std::vector<std::vector<uint32_t>>> getCpuFreqs() {
+    if (!gInitialized && !initGlobals()) return {};
+    return gPolicyFreqs;
+}
+
 // Retrieve the times in ns that uid spent running at each CPU frequency.
 // Return contains no value on error, otherwise it contains a vector of vectors using the format:
 // [[t0_0, t0_1, ...],
diff --git a/libs/cputimeinstate/cputimeinstate.h b/libs/cputimeinstate/cputimeinstate.h
index f620715dab..49469d8e04 100644
--- a/libs/cputimeinstate/cputimeinstate.h
+++ b/libs/cputimeinstate/cputimeinstate.h
@@ -26,6 +26,7 @@ bool startTrackingUidTimes();
 std::optional<std::vector<std::vector<uint64_t>>> getUidCpuFreqTimes(uint32_t uid);
 std::optional<std::unordered_map<uint32_t, std::vector<std::vector<uint64_t>>>>
     getUidsCpuFreqTimes();
+std::optional<std::vector<std::vector<uint32_t>>> getCpuFreqs();
 
 struct concurrent_time_t {
     std::vector<uint64_t> active;
diff --git a/libs/cputimeinstate/testtimeinstate.cpp b/libs/cputimeinstate/testtimeinstate.cpp
index c0cd3e07ff..30722de0c1 100644
--- a/libs/cputimeinstate/testtimeinstate.cpp
+++ b/libs/cputimeinstate/testtimeinstate.cpp
@@ -351,5 +351,16 @@ TEST(TimeInStateTest, RemoveUid) {
     ASSERT_EQ(allConcurrentTimes->find(uid), allConcurrentTimes->end());
 }
 
+TEST(TimeInStateTest, GetCpuFreqs) {
+    auto freqs = getCpuFreqs();
+    ASSERT_TRUE(freqs.has_value());
+
+    auto times = getUidCpuFreqTimes(0);
+    ASSERT_TRUE(times.has_value());
+
+    ASSERT_EQ(freqs->size(), times->size());
+    for (size_t i = 0; i < freqs->size(); ++i) EXPECT_EQ((*freqs)[i].size(), (*times)[i].size());
+}
+
 } // namespace bpf
 } // namespace android