From d0de6fdfa8312147e7d991cf5326e3394b9abf3c Mon Sep 17 00:00:00 2001 From: Sebastian Huber Date: Thu, 15 Jul 2021 16:51:17 +0200 Subject: score: Add _IO_Relax() This function may be used to burn a couple of processor cycles with minimum impact on the system bus. It may be used in busy wait loops. Since it is a global function, it is possible to wrap it in device driver test code. --- cpukit/include/rtems/score/io.h | 8 ++++++ cpukit/score/src/iorelax.c | 53 +++++++++++++++++++++++++++++++++++++++ spec/build/cpukit/librtemscpu.yml | 1 + 3 files changed, 62 insertions(+) create mode 100644 cpukit/score/src/iorelax.c diff --git a/cpukit/include/rtems/score/io.h b/cpukit/include/rtems/score/io.h index d7bf188be0..106418f185 100644 --- a/cpukit/include/rtems/score/io.h +++ b/cpukit/include/rtems/score/io.h @@ -133,6 +133,14 @@ int _IO_Base64url( int wordlen ); +/** + * @brief Issues a couple of no-operation instructions. + * + * This function may be used to burn a couple of processor cycles with minimum + * impact on the system bus. It may be used in busy wait loops. + */ +void _IO_Relax( void ); + /** @} */ #ifdef __cplusplus diff --git a/cpukit/score/src/iorelax.c b/cpukit/score/src/iorelax.c new file mode 100644 index 0000000000..f37d848605 --- /dev/null +++ b/cpukit/score/src/iorelax.c @@ -0,0 +1,53 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ + +/** + * @file + * + * @ingroup RTEMSScoreIO + * + * @brief This source file contains the implementation of _IO_Relax(). + */ + +/* + * Copyright (C) 2021 embedded brains GmbH (http://www.embedded-brains.de) + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include +#include + +void _IO_Relax( void ) +{ + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); + _CPU_Instruction_no_operation(); +} diff --git a/spec/build/cpukit/librtemscpu.yml b/spec/build/cpukit/librtemscpu.yml index c224937348..965419c389 100644 --- a/spec/build/cpukit/librtemscpu.yml +++ b/spec/build/cpukit/librtemscpu.yml @@ -1418,6 +1418,7 @@ source: - cpukit/score/src/interr.c - cpukit/score/src/iobase64.c - cpukit/score/src/ioprintf.c +- cpukit/score/src/iorelax.c - cpukit/score/src/iovprintf.c - cpukit/score/src/isr.c - cpukit/score/src/isrisinprogress.c -- cgit v1.2.3