Media Processor-based Real-time Operating System Design Study

As an application hotspot, multimedia application also greatly improves the development of IC industry. With the powerful processing ability, programmable media signal processor has been more and more important in the application. The real time operating system (RTOS) can not only improve the performance and reliability of the media processor SOC, but also simplify the development and debugging of media processor SOC. There is a growing consensus that RTOS has become an indispensable part of SOC. We designed and realized a real-time operating system, named Iota, for media processor. MediaDSP3200 (MD32) is the prototype media processor.The real-time microkernel we designed includes the following parts: task management, synchronization and communication, memory management, time management, interrupt handling and system call. The real-time microkernel supports 16 tasks. The preemptive scheduling mechanism is adopted for the real-time tasks. Iota utilizes semaphore to synchronize the access of shared resource and execution order of processes. Mutex exclusion semaphore is implemented for avoiding the priority inversion. According to the characteristics of processor MMU, a simple memory protection and sharing mechanical is designed. Iota also supplies a dynamic memory management mechanism to meet dynamic memory allocation need for some programs. Time management offers time function for tasks, and the system can read and set the time. Interrupt handling is implemented for the system to find and repair system or user program errors. System call is implemented for tasks to enter kernel space and execute system service.A simple file management is completed in Iota. A device can be operated and managed as a file. Because of the existence of file management, Iota can ignore the characteristics of the hardware platform and regard the hardware devices as the files, so it can be easy to be migrated for the other hardware platform. Because the data of media processing is large, a simple network protocol is also implemented to speedup the data transmission between the host machine to the target platform when we simulate the media processing program.We present a methodology for software/hardware co-verification based on RTOS according to the characteristic of our media processor chip. A co-verification platform based on RTOS is the basic and vital elements in this methodology and could be migrated easily. In the phase of chip designing, we establish a software verification platform whose hardware is close to our chip. We verify the correctness of software in this co-verification platform, then use this correct software to verify the correctness of chip in the hardware verification platform. Adopting this methodology, it could not only verify the correctness of the chip and reduce the possibility of the errors in the chip, but also shorten the co-verification time.