Intel IXP400 Digital Signal Processing (DSP) Software: Priority Setting for 10 ms Real Time Task

Transcription

1 Intel IXP400 Digital Signal Processing (DSP) Software: Priority Setting for 10 ms Real Time Task Application Note November 2005 Document Number: , Revision: 001 November 2005

2 Legal Notice INFORMATION IN THIS DOCUMENT IS PROVIDED IN CONNECTION WITH INTEL PRODUCTS. EXCEPT AS PROVIDED IN INTEL S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, INTEL ASSUMES NO LIABILITY WHATSOEVER, AND INTEL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO SALE AND/OR USE OF INTEL PRODUCTS, INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT, OR OTHER INTELLECTUAL PROPERTY RIGHT. Intel Corporation may have patents or pending patent applications, trademarks, copyrights, or other intellectual property rights that relate to the presented subject matter. The furnishing of documents and other materials and information does not provide any license, express or implied, by estoppel or otherwise, to any such patents, trademarks, copyrights, or other intellectual property rights. Intel products are not intended for use in medical, life saving, life sustaining, critical control or safety systems, or in nuclear facility applications. Intel may make changes to specifications and product descriptions at any time, without notice. Designers must not rely on the absence or characteristics of any features or instructions marked reserved or undefined. Intel reserves these for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to them. This Application Note as well as the software described in it is furnished under license and may only be used or copied in accordance with the terms of the license. The information in this manual is furnished for informational use only, is subject to change without notice, and should not be construed as a commitment by Intel Corporation. Intel Corporation assumes no responsibility or liability for any errors or inaccuracies that may appear in this document or any software that may be provided in association with this document. Except as permitted by such license, no part of this document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means without the express written consent of Intel Corporation. Contact your local Intel sales office or your distributor to obtain the latest specifications and before placing your product order. Copies of documents which have an ordering number and are referenced in this document, or other Intel literature may be obtained by calling or by visiting Intel's website at Intel and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. *Other names and brands may be claimed as the property of others. Copyright 2005, Intel Corporation November 2005 Priority Setting for 10 ms Real Time Task Application Note 2 Document Number: , Revision: 001

3 Contents 1.0 Introduction Scope Related Documents Acronyms Priority Setting for 10 ms Real Time Task in Linux* Priority Setting for 10 ms Real Time Task in VxWorks* Conclusion...8 Figures 1 Intel IXP400 DSP Software Message, Data, and Tasks...6 Revision History Date Revision Description November Initial release of document. Application Note Priority Setting for 10 ms Real Time Task November 2005 Document Number: , Revision: 001 3

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5 1.0 Introduction During initialization of Intel IXP400 DSP Software, real-time tasks are created. The 10- millisecond (ms) Real Time Task is created to process data flows for G.711 and G.729 coders, and handles all other non-coder voice processing, such as echo cancellation and tone detection. If 10 ms Real Time Task cannot finish its processing before the next task period, voice quality is degraded. Setting the priority for the Task is one of the ways to ensure that it has higher priority when scheduled for execution. 1.1 Scope This application note is intended to explain how to set the priority for 10 ms Real Time Task of Intel IXP400 DSP Software v Further information can be found in the documents shown in Section Related Documents Document Intel IXP400 Digital Signal Processing (DSP) Software Version API Reference Manual Intel IXP400 Digital Signal Processing (DSP) Software Version Programmer s Guide Intel IXP400 Digital Signal Processing (DSP) Software Version Release Notes Document Number N/A 1.3 Acronyms Acronym API DSP HSS ISR NPE PCM Description Application Programming Interface Digital Signal Processing High Speed Serial Interrupt Service Routine Network Processing Engine Pulse Code Modulation 2.0 Priority Setting for 10 ms Real Time Task in Linux* The DSP software creates 10 ms Real Time Task to generate or consume audio data at 10 ms intervals essentially synchronized with PCM data from HSS NPE or external PCM device. See Figure 1. Application Note Priority Setting for 10 ms Real Time Task November 2005 Document Number: , Revision: 001 5

6 Figure 1. Intel IXP400 DSP Software Message, Data, and Tasks Intel IXP400 DSP Software Module Intel IXP400 DSP Software Client Application Control Task Control Messages Interrupt Ethernet NPE IP Packets SLIC Interface HSS NPE or External PCM device 8-bit PCM Data Interrupt HSS Buffer 16-bit PCM Data Scheduler Real-Time Task Job Management Egress Encoded Packets Jitter Buffer IP Stack IP ISR IP Task Ingress Encoded Packets B The HSS NPE or External PCM device generates an interrupt every 10 ms. The ISR services HSS buffers (copy data to/from the buffers), update the job queue and update other parameters such as time stamp. The Linux* Kernel Scheduler uses the job queue for scheduling any pending task to run. It is possible that the 10 ms Real Time Task is delayed under certain conditions. This condition will happen when there are multiple tasks having higher priority than the 10 ms Real Time Task or the current active task, having the same or higher priority than the 10 ms Real Time Task execute for more than 10 ms. This will affect the performance of the DSP software and affect the overall voice quality. Hence, it is important to ensure that 10 ms Real Time Task has the highest priority. Other tasks should have a lower priority and should not execute for a period longer than 10 ms. To change the static priority of 10 ms Real Time Task: For IXP400 Software Release Version 1.3, modify ixp425_xscale_sw/src/linux/vx.c For IXP400 Software Release Version 1.4, modify ixp400_xscale_sw/src/linux/vx.c November 2005 Priority Setting for 10 ms Real Time Task Application Note 6 Document Number: , Revision: 001

7 #include <linux/slab.h> #include <asm/uaccess.h> #include vx.h int taskspawn(char *name, int priority, int options, int stack_sz, FUNCPTR entry_pt, int arg1, int arg2, int arg3, int arg4, int arg5, int arg6, int arg7, int arg8, int arg9, int arg10) { pid_t pid; int retval = -2; struct sched_param prm2; mm_segment_t fs; long policy; down(&data_mutex); if (pid < 0) { up(&data_mutex); return ERROR; } /* To set the priority if the task spawned is 10ms Real Time Task */ if (strncmp(task_data.name, DspRtTsk10, sizeof(task_data.name)) == 0) { fs = get_fs(); set_fs(get_ds()); } } return (int)pid; /*Choose a static priority within the valid range (1 to 99)*/ prm2.sched_priority= 10; /* Please choose either SCHED_RR or SCHED_FIFO when calling setscheduler*/ retval = setscheduler (pid, SCHED_RR, &prm2); set_fs(fs); if (retval ==0) { printk ( Successfully set 10ms Real Time Task Priority );} else {printk ( Error in setting 10ms Real Time Task Priority );} After modification, ixp400.o needs to be recompiled. Please refer to the Intel IXP400 DSP Software v2.6.2 Release Notes for steps on how to compile ixp400.o. Application Note Priority Setting for 10 ms Real Time Task November 2005 Document Number: , Revision: 001 7

8 3.0 Priority Setting for 10 ms Real Time Task in VxWorks* 10 ms Real Time Task in VxWorks* can be set by providing appropriate base priority setting during initialization stage of calling xdspsysinit() function. Please see the Intel IXP400 Digital Signal Processing (DSP) Software Version API Reference Manual for more details. 4.0 Conclusion The 10 ms Real Time Task priority for DSP software release can be set accordingly in Linux by modifying vx.c file, and in VxWorks by providing appropriate base priority during initialization. November 2005 Priority Setting for 10 ms Real Time Task Application Note 8 Document Number: , Revision: 001