Last week, we continued our  series of posts on the topic of “portable stimulus” as defined by Accellera’s Portable Stimulus Working Group (PSWG) and the standard they are working to define. We should say “we are working to define” since Breker is very much a part of the effort and is providing our many years of experience in this area to develop the best possible industry solution. As a reminder, we at Breker split the definition of a standard for portable stimulus into three parts: defining the tests using abstract primitive operations, scheduling the tests across multiple threads and multiple processors, and randomizing the control flow to verify the full range of realistic use-case scenarios.

Our most recent post dealt with the first layer: defining abstract tests using primitive operations and other elements within a base-class library, with access defined by a simple application programming interface (API). This week we consider the second layer: scheduling of tests and resources. If a verification engineer is writing a directed test for a single-processor SoC using the API calls from the first layer, then little of the second layer may apply. However, as we have discussed before, there is a clear trend of SoC designs moving to multi-processor designs with complex memory and cache subsystems and a rich variety of I/O protocols. These chips require automated test generation and the features provided by the test scheduling layer.

(more…)

In our last blog post we provided some updates on the ongoing effort by Accellera to standardize “portable stimulus” in its Portable Stimulus Working Group (PSWG). We mentioned our three guiding precepts as we participate in, and help lead, this industry effort:

• Portable stimulus is not enough;  portable tests must encompass stimulus, results checking, and coverage
• Test portability must encompass both vertical reuse from IP to SoC and horizontal reuse across all verification platforms
• The tests themselves are not portable, but are generated for multiple targets from an abstract specification of the verification space

We stated our view that the goal of the portable stimulus effort can be split into three parts: defining the tests using abstract primitive operations, scheduling the tests across multiple threads and multiple processors, and randomizing the control flow to verify the full range of realistic use-case scenarios. We mentioned that the first part can be can be standardized using a simple application programming interface (API) to specify the abstract steps of the test. We have also found that the scheduling part can be handled by an expanded API. The user might want to specify the available resources and how they should be used in a particular test, for example, the number of threads running on each processor. When it comes to the third part, the randomization, an API might be feasible but there a number of candidate formats. We’d like to spend the remainder of this post examining these options.

(more…)