title: “ENTROPY_SRC dv document”

Goals

  • DV
    • Verify all ENTROPY_SRC IP features by running dynamic simulations with a SV/UVM based testbench
    • Develop and run all tests based on the testplan below towards closing code and functional coverage on the IP and all of its sub-modules
  • FPV
    • Verify TileLink device protocol compliance with an SVA based testbench

Current status

  • [Design & verification stage]({{< relref “hw” >}})
    • [HW development stages]({{< relref “doc/project/development_stages” >}})
  • Simulation results

Design features

For detailed information on ENTROPY_SRC design features, please see the [ENTROPY_SRC HWIP technical specification]({{< relref “hw/ip/entropy_src/doc” >}}).

Testbench architecture

ENTROPY_SRC testbench has been constructed based on the [CIP testbench architecture]({{< relref “hw/dv/sv/cip_lib/doc” >}}).

Block diagram

Block diagram

Top level testbench

Top level testbench is located at hw/ip/entropy_src/dv/tb/tb.sv. It instantiates the ENTROPY_SRC DUT module hw/ip/entropy_src/rtl/entropy_src.sv. In addition, it instantiates the following interfaces, connects them to the DUT and sets their handle into uvm_config_db:

  • [Clock and reset interface]({{< relref “hw/dv/sv/common_ifs” >}})
  • [TileLink host interface]({{< relref “hw/dv/sv/tl_agent/README.md” >}})
  • ENTROPY_SRC IOs
  • Interrupts ([pins_if]({{< relref “hw/dv/sv/common_ifs” >}})

Common DV utility components

The following utilities provide generic helper tasks and functions to perform activities that are common across the project:

  • [common_ifs]({{< relref “hw/dv/sv/common_ifs” >}})
  • [dv_utils_pkg]({{< relref “hw/dv/sv/dv_utils/README.md” >}})
  • [csr_utils_pkg]({{< relref “hw/dv/sv/csr_utils/README.md” >}})

Global types & methods

All common types and methods defined at the package level can be found in entropy_src_env_pkg. Some of them in use are:

TL_agent
ENTROPY_SRC testbench instantiates (already handled in CIP base env) [tl_agent]({{< relref “hw/dv/sv/tl_agent/README.md” >}}) which provides the ability to drive and independently monitor random traffic via TL host interface into ENTROPY_SRC device.
UVM RAL Model
The ENTROPY_SRC RAL model is created with the [ralgen]({{< relref “hw/dv/tools/ralgen/README.md” >}}) FuseSoC generator script automatically when the simulation is at the build stage.
It can be created manually (separately) by running make in the hw/ area.
Stimulus strategy
Test sequences
All test sequences reside in hw/ip/entropy_src/dv/env/seq_lib. The entropy_src_base_vseq virtual sequence is extended from cip_base_vseq and serves as a starting point. All test sequences are extended from entropy_src_base_vseq. It provides commonly used handles, variables, functions and tasks that the test sequences can simple use / call. Some of the most commonly used tasks / functions are as follows:
  • entropy_src_init:     Initialize the ENTROPY_SRC module from the randomized environment variables in the config.
Functional coverage
To ensure high quality constrained random stimulus, it is necessary to develop a functional coverage model. The following covergroups have been developed to prove that the test intent has been adequately met:
  • common covergroup for interrupts hw/dv/sv/cip_lib/cip_base_env_cov.sv: Cover interrupt value, interrupt enable, intr_test, interrupt pin
Self-checking strategy
Scoreboard
The entropy_src_scoreboard is primarily used for end to end checking. It creates the following analysis ports to retrieve the data monitored by corresponding interface agents:
  • tl_a_chan_fifo, tl_d_chan_fifo:           These 2 fifos provide transaction items at the end of Tilelink address channel and data channel respectively
Assertions
  • TLUL assertions: The tb/entropy_src_bind.sv binds the tlul_assert [assertions]({{< relref “hw/ip/tlul/doc/TlulProtocolChecker.md” >}}) to the IP to ensure TileLink interface protocol compliance.
  • Unknown checks on DUT outputs: The RTL has assertions to ensure all outputs are initialized to known values after coming out of reset.
Building and running tests
We are using our in-house developed [regression tool]({{< relref “hw/dv/tools/README.md” >}}) for building and running our tests and regressions. Please take a look at the link for detailed information on the usage, capabilities, features and known issues. Here's how to run a smoke test:
$ cd hw/ip/entropy_src/dv
$ make TEST_NAME=entropy_src_smoke

Testplan
{{< testplan “hw/ip/entropy_src/data/entropy_src_testplan.hjson” >}}