New-Tech Europe | April 2016 | Digital edition

AMP up Your Next SoC Project Harness real-time performance and the rich features of Linux

Scott McNutt, Senior Software Engineer

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assured that the Linux development community has introduced many features into the kernel that greatly simplify AMP configuration and use. LINUX MULTIPROCESSING IN A NUTSHELL With respect to multiprocessing, the Linux kernel comes in two flavors: the uniprocessor (UP) kernel and the symmetric multiprocessor (SMP) kernel. The UP kernel can only run on a single core, regardless of the number of available cores. AMP systems can incorporate two or more instances of the uniprocessor kernel. The SMP kernel, however, can run on one core or simultaneously on multiple cores (Figure 1). An optional kernel command line parameter controls the number of cores used by the SMP kernel following system initialization. Once the kernel is running, various command line utilities control the number of cores assigned to the

We can use these SoC products as the basis of a Linux/RTOS AMP system that provides considerable flexibility. In many ways, the typical AMP configuration is similar to a PCI- based system, with the Linux domain functioning as the host, the RTOS domain functioning as an adapter, and one or more shared memory regions used for communication between the two domains. Unlike PCI, however, an AMP configuration can more conveniently- and dynamically-assign resources (both the standard peripherals and custom logic) to one domain or the other. In addition, a Linux/RTOS AMP system can dynamically reconfigure programmable logic based on runtime requirements, such as the presence or absence of various external devices. This level of flexibility is often coupled with concerns about complexity and the degree of difficulty involved in bringing up an AMP system. Rest

mbedded systems usually fall into one of two categories:

those that require hard real-time performance and those that don’t. In the past, we had to pick our poison-the performance of our “go to” real-time operating system or the rich feature set of our favorite Linux distribution-and then struggle with its shortcomings. Today, embedded developers no longer need to choose between the two. Asymmetric multiprocessing (AMP) offers the best of both worlds. Several modern system-on-chip (SoC) product offerings integrate multiple CPUs, a broad variety of standard I/O peripherals and programmable logic. The Xilinx® Zynq-7000® All Programmable SoC family, for example, includes a dual-core ARM® Cortex™-A9, standard peripherals (such as Gigabit Ethernet MACs, USB, DMA, SD/MMC, SPI and CAN) and a large programmable logic array.

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