Kernel Clock Minimum Frequency - 2022.2 English

Vitis Guidance Messaging (UG1315)

Document ID
UG1315
Release Date
2022-10-19
Version
2022.2 English

Description

Auto frequency scaling failed. The maximum kernel frequency, based on the given kernel implementation, is lower than the minimum frequency supported by the run time.

Explanation

The automatic frequency scaling feature allows user kernels to operate in hardware, even at a lower frequency than intended. However, nothing slower than the minimum frequency can operate in hardware.

Recommendation

In general, xocc supports the –kernel_frequency option, which allows the definition of the kernel frequency for synthesis. Alternatively, clock uncertainty can be used to influence how much time is available for the HLS scheduler to schedule operations within a cycle. Either way, the resulting schedule can be influenced to operate at a higher frequency using these options.

Note: Slack values, including WNS values, have an associated sign. A negative slack value has failed to meet timing. A zero or positive slack value typically passes the timing check; the possible exception being when the threshold value is also a positive value.