[zephyr] Do not initialize real time clock (#20490) (#20505)

When there was no support for Last Known UTC Time in the common code we added a similar but incomplete solution to the Zephyr platform code that initializes the real time clock to the firmware build time. That solution is incorrect as it doesn't allow for updating the Last Known UTC Time, so we should rather return an error if no time synchronization is in place. Signed-off-by: Damian Krolik <[email protected]> Co-authored-by: Damian Królik <[email protected]>
project-chip · Jul 9, 2022 · 6874156 · 6874156
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commit 6874156
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Showing 5 changed files with 10 additions and 30 deletions.
diff --git a/config/nrfconnect/chip-module/CMakeLists.txt b/config/nrfconnect/chip-module/CMakeLists.txt
@@ -236,11 +236,6 @@ if (CONFIG_CHIP_ENABLE_DNSSD_SRP)
     chip_gn_arg_string("chip_mdns" "platform")
 endif()
 
-if (CONFIG_CHIP_FIRMWARE_BUILD_UNIX_TIME)
-    string(TIMESTAMP CHIP_FIRMWARE_BUILD_UNIX_TIME "%s")
-    chip_gn_arg_string("chip_device_config_firmware_build_unix_time" ${CHIP_FIRMWARE_BUILD_UNIX_TIME})
-endif()
-
 if (CHIP_PROJECT_CONFIG)
     chip_gn_arg_string("chip_project_config_include"        ${CHIP_PROJECT_CONFIG})
     chip_gn_arg_string("chip_system_project_config_include" ${CHIP_PROJECT_CONFIG})

diff --git a/config/zephyr/Kconfig b/config/zephyr/Kconfig
@@ -229,13 +229,6 @@ config CHIP_MALLOC_SYS_HEAP_SIZE
 
 endif
 
-config CHIP_FIRMWARE_BUILD_UNIX_TIME
-	bool "Make Unix time of compilation available in source code"
-	default y
-	help
-	  When enabled, the Unix time of the firmware build is exposed to the
-	  source code and used to initialize the last known UTC time.
-
 config APP_LINK_WITH_CHIP
 	bool "Link 'app' with Connected Home over IP"
 	default y

diff --git a/scripts/examples/nrfconnect_example.sh b/scripts/examples/nrfconnect_example.sh
@@ -23,7 +23,7 @@ BOARD="$2"
 shift 2
 
 # Disable debug symbols and firmware build time to increase ccache hit ratio in CI
-COMMON_CI_FLAGS=(-DCONFIG_CHIP_DEBUG_SYMBOLS=n -DCONFIG_CHIP_FIRMWARE_BUILD_UNIX_TIME=n)
+COMMON_CI_FLAGS=(-DCONFIG_CHIP_DEBUG_SYMBOLS=n)
 
 if [[ ! -f "$APP/nrfconnect/CMakeLists.txt" || -z "$BOARD" ]]; then
     echo "Usage: $0 <application> <board>" >&2

diff --git a/src/platform/BUILD.gn b/src/platform/BUILD.gn
@@ -41,9 +41,6 @@ if (chip_device_platform != "none" && chip_device_platform != "external") {
     # Time the firmware was built.
     chip_device_config_firmware_build_time = ""
 
-    # Unix time the firmware was built at (seconds since the epoch)
-    chip_device_config_firmware_build_unix_time = ""
-
     # Use OpenThread ftd or mtd library
     chip_device_config_thread_ftd = chip_openthread_ftd
 
@@ -142,9 +139,6 @@ if (chip_device_platform != "none" && chip_device_platform != "external") {
     if (chip_device_config_firmware_build_time != "") {
       defines += [ "CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_TIME=\"${chip_device_config_firmware_build_time}\"" ]
     }
-    if (chip_device_config_firmware_build_unix_time != "") {
-      defines += [ "CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_UNIX_TIME=${chip_device_config_firmware_build_unix_time}" ]
-    }
 
     if (chip_use_transitional_commissionable_data_provider) {
       defines += [ "CHIP_USE_TRANSITIONAL_COMMISSIONABLE_DATA_PROVIDER=1" ]

diff --git a/src/platform/Zephyr/SystemTimeSupport.cpp b/src/platform/Zephyr/SystemTimeSupport.cpp
@@ -42,15 +42,10 @@ ClockImpl gClockImpl;
 
 namespace {
 
-// Last known UTC time in Unix format.
-#ifdef CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_UNIX_TIME
-Microseconds64 gRealTime = Seconds64(CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_UNIX_TIME);
-#else
-Microseconds64 gRealTime = Seconds64(CHIP_SYSTEM_CONFIG_VALID_REAL_TIME_THRESHOLD);
-#endif
+constexpr Microseconds64 kUnknownRealTime = Seconds64::zero();
 
-// Monotonic time of setting the last known UTC time.
-Microseconds64 gRealTimeSetTime;
+// Unix epoch time of boot event
+Microseconds64 gBootRealTime = kUnknownRealTime;
 
 } // namespace
 
@@ -66,7 +61,11 @@ Milliseconds64 ClockImpl::GetMonotonicMilliseconds64()
 
 CHIP_ERROR ClockImpl::GetClock_RealTime(Microseconds64 & aCurTime)
 {
-    aCurTime = GetMonotonicMicroseconds64() - gRealTimeSetTime + gRealTime;
+    // The real time can be configured by an application if it has access to a reliable time source.
+    // Otherwise, just return an error so that Matter stack can fallback to Last Known UTC Time.
+    ReturnErrorCodeIf(gBootRealTime == kUnknownRealTime, CHIP_ERROR_INCORRECT_STATE);
+
+    aCurTime = gBootRealTime + GetMonotonicMicroseconds64();
 
     return CHIP_NO_ERROR;
 }
@@ -83,8 +82,7 @@ CHIP_ERROR ClockImpl::GetClock_RealTimeMS(Milliseconds64 & aCurTime)
 
 CHIP_ERROR ClockImpl::SetClock_RealTime(Microseconds64 aNewCurTime)
 {
-    gRealTime        = aNewCurTime;
-    gRealTimeSetTime = GetMonotonicMicroseconds64();
+    gBootRealTime = aNewCurTime - GetMonotonicMicroseconds64();
 
     return CHIP_NO_ERROR;
 }