Ewout van Bekkum | 41daf16 | 2021-03-03 13:57:28 -0800 | [diff] [blame] | 1 | // Copyright 2021 The Pigweed Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 4 | // use this file except in compliance with the License. You may obtain a copy of |
| 5 | // the License at |
| 6 | // |
| 7 | // https://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| 11 | // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 12 | // License for the specific language governing permissions and limitations under |
| 13 | // the License. |
| 14 | |
| 15 | #include "pw_chrono/system_clock.h" |
| 16 | |
| 17 | #include <atomic> |
| 18 | #include <chrono> |
| 19 | #include <limits> |
| 20 | #include <mutex> |
| 21 | |
| 22 | #include "RTOS.h" |
Ewout van Bekkum | da2a62d | 2021-03-12 11:34:47 -0800 | [diff] [blame] | 23 | #include "pw_sync/interrupt_spin_lock.h" |
Ewout van Bekkum | 41daf16 | 2021-03-03 13:57:28 -0800 | [diff] [blame] | 24 | |
| 25 | namespace pw::chrono::backend { |
| 26 | namespace { |
| 27 | |
Ewout van Bekkum | da2a62d | 2021-03-12 11:34:47 -0800 | [diff] [blame] | 28 | sync::InterruptSpinLock system_clock_interrupt_spin_lock; |
Ewout van Bekkum | 41daf16 | 2021-03-03 13:57:28 -0800 | [diff] [blame] | 29 | int64_t overflow_tick_count = 0; |
| 30 | uint32_t native_tick_count = 0; |
| 31 | static_assert(!SystemClock::is_nmi_safe, |
| 32 | "global state is not atomic nor double buferred"); |
| 33 | |
| 34 | static_assert(sizeof(void*) == 4, "this backend only supports 32 bit targets!"); |
| 35 | |
| 36 | inline uint32_t GetUint32TickCount() { |
| 37 | // embOS returns a signed 32 bit value, however according to their developers |
| 38 | // the binary value continues to increment like an unsigned value, ergo we |
| 39 | // instead reinterpret the tick count as the raw underlying 32 bit unsigned |
| 40 | // tick count. |
| 41 | return static_cast<uint32_t>(OS_GetTime32()); |
| 42 | } |
| 43 | |
| 44 | // The tick count resets to 0, ergo the overflow count is the max count + 1. |
| 45 | constexpr int64_t kNativeOverflowTickCount = |
| 46 | static_cast<int64_t>(std::numeric_limits<uint32_t>::max()) + 1; |
| 47 | |
| 48 | } // namespace |
| 49 | |
| 50 | int64_t GetSystemClockTickCount() { |
Ewout van Bekkum | da2a62d | 2021-03-12 11:34:47 -0800 | [diff] [blame] | 51 | std::lock_guard lock(system_clock_interrupt_spin_lock); |
Ewout van Bekkum | 41daf16 | 2021-03-03 13:57:28 -0800 | [diff] [blame] | 52 | const uint32_t new_native_tick_count = GetUint32TickCount(); |
| 53 | // WARNING: This must be called more than once per overflow period! |
| 54 | if (new_native_tick_count < native_tick_count) { |
| 55 | // Native tick count overflow detected! |
| 56 | overflow_tick_count += kNativeOverflowTickCount; |
| 57 | } |
| 58 | native_tick_count = new_native_tick_count; |
| 59 | return overflow_tick_count + native_tick_count; |
| 60 | } |
| 61 | |
| 62 | } // namespace pw::chrono::backend |