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UART DV document

Goals

  • DV
    • Verify all UART 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 features

For detailed information on UART design features, please see the UART design specification.

Testbench architecture

UART testbench has been constructed based on the CIP testbench architecture.

Block diagram

Block diagram

Top level testbench

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

Common DV utility components

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

Global types & methods

All common types and methods defined at the package level can be found in uart_env_pkg.

TL_agent

UART instantiates (already handled in CIP base env) tl_agent which provides the ability to drive and independently monitor random traffic via TL host interface into UART device.

UART agent

UART agent is used to drive and monitor UART items, which also provides basic coverage on data, parity, baud rate etc. These baud rates are supported: 9600, 115200, 230400, 1Mbps(1048576), 2Mbps(2097152)

UVM RAL Model

The UART RAL model is created with the ralgen FuseSoC generator script automatically when the simulation is at the build stage.

It can be created manually by invoking regtool:

Stimulus strategy

Test sequences

All test sequences reside in hw/ip/uart/dv/env/seq_lib. The uart_base_vseq virtual sequence is extended from cip_base_vseq and serves as a starting point. All test sequences are extended from uart_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:

  • uart_init: Configure uart control and fifo related csr with random values
  • send_tx_byte: Program one TX byte to enable DUT to send a TX byte to UART interface
  • send_rx_byte: Drive a RX byte to DUT through UART interface

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
  • uart_cg in uart_agent_cov hw/dv/sv/uart_agent/uart_agent_cov.sv: Cover direction, uart data, en_parity, odd_parity and baud rate
  • rx_fifo_level_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover all fifo level with fifo reset for RX
  • tx_fifo_level_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover all fifo level with fifo reset for TX
  • tx_watermark_cg / rx_watermark_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover TX/RX watermark interrupt triggered for all watermark levels
  • rx_break_err_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover break interrupt triggered for all break levels
  • rx_timeout_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover timeout interrupt with small ( < 20), medium (20 - 50) and large (50 - 100) timeout values
  • rx_parity_err_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover parity interrupt with both even and odd parity
  • noise_filter_cg hw/ip/uart/dv/env/uart_env_cov.sv: Cover all combinations of bits in the noise filter

Self-checking strategy

Scoreboard

The uart_scoreboard is primarily used for end to end checking. It creates the following analysis fifos to retrieve the data monitored by corresponding interface agents:

  • tl_a_chan_fifo, tl_d_chan_fifo: These 2 fifos provides transaction items at the end of address channel and data channel respectively
  • uart_tx_fifo, uart_rx_fifo: These 2 fifos provides UART TX and RX item when its transfer completes

Assertions

  • TLUL assertions: The tb/uart_bind.sv binds the tlul_assert assertions 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 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:

$ $REPO_TOP/util/dvsim/dvsim.py $REPO_TOP/hw/ip/uart/dv/uart_sim_cfg.hjson -i uart_smoke

Testplan

Testplan