Fix-Point commented on code in PR #17316: URL: https://github.com/apache/nuttx/pull/17316#discussion_r2525651464
########## include/nuttx/timers/clkcnt.h: ########## @@ -0,0 +1,451 @@ +/**************************************************************************** + * include/nuttx/timers/clkcnt.h + * + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. The + * ASF licenses this file to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +#ifndef __INCLUDE_NUTTX_TIMERS_CLKCNT_H +#define __INCLUDE_NUTTX_TIMERS_CLKCNT_H + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <assert.h> +#include <stdint.h> + +#include <nuttx/clock.h> +#include <nuttx/compiler.h> +#include <nuttx/lib/math32.h> + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +#define CLKCNT_MAX UINT64_MAX + +/**************************************************************************** + * Public Types + ****************************************************************************/ + +typedef uint64_t clkcnt_t; Review Comment: `clkcnt_t` is designed for representing the physical timer count, most of them are 64-bit, including: - x86 tsc-deadline https://wiki.osdev.org/APIC_Timer - x86 hpet https://wiki.osdev.org/HPET - arm generic timer(armv7a/v7r/v8r/v8a) https://developer.arm.com/documentation/102379/0104/What-is-the-Generic-Timer- - PowerPC Time Base/PIT https://wiki.raptorcs.com/w/images/9/9b/405_um.pdf - risc-v machine timer https://www.cs.cornell.edu/courses/cs4411/2022fa/schedule/slides/week5_timer_interrupt.pdf - tricore systimer [tricore reference manual] - loongarch timer https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.pdf Adding `32-bits clkcnt` may improve the performance of some rare timers, but it increases the complexity of the implementation. You need to consider issues like multiplication overflow in the 32-bit case. If you are familiar with the functional safety standards `IEC 61508`, `ISO 26262`, or `DO 178`, you should know that to ensure system functional-correctness, we should simplify the implementation as much as possible. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
