RV_TIMER DV document
- Verify all RV_TIMER IP features by running dynamic simulations with a SV/UVM based testbench
- Develop and run all tests based on the DV plan below towards closing code and functional coverage on the IP and all of its sub-modules
- Verify TileLink device protocol compliance with an SVA based testbench
For detailed information on RV_TIMER design features, please see the RV_TIMER design specification.
RV_TIMER testbench has been constructed based on the CIP testbench architecture.
Top level testbench
Top level testbench is located at
hw/ip/rv_timer/dv/tb/tb.sv. It instantiates the RV_TIMER DUT module
In addition, it instantiates the following interfaces, connects them to the DUT and sets their handle into
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
Some of them in use are:
parameter uint NUM_HARTS = 1; parameter uint NUM_TIMERS = 1;
RV_TIMER testbench 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 RV_TIMER device.
UVM RAL Model
The RV_TIMER 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
All test sequences reside in
rv_timer_base_vseq virtual sequence is extended from
cip_base_vseq and serves as a starting point.
All test sequences are extended from
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:
cfg_timer: set a particular timer active or inactive
cfg_hart: set timer step and prescale values
intr_state_spinwait: poll a intr_status randomly until it reads the expected value
status_read_for_clks: read intr_status register randomly for num clks
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:
timer_cfg_cg: cover group define bins for timer config parameters
timer_active_cg: cover group define bin all timers active at same time
rv_timer_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 address channel
- tl_d_chan_fifo: tl data channel
rv_timer scoreboard monitors all CSR registers and interrupt pins.
For a write transaction, during the address channel, CSR values are updated in RAL and config values (timer enable, step, prescale, timer value, compare value) are updated in internal arrays. When particular timer is enabled, rv_timer scoreboard calculate timeout clocks and start a thread to wait for timeout, then if any of timer configuration updated on active timer, rv_timer scoreboard recalculate and update the timeout clocks in ther running timeout thread. If multiple timers are enabled, multipe threads will be initiated. On timeout scoreboard calculate the expected interrupt status and update RAL registers.
For a read transaction, during the address channel for interrupt status CSR rv_timer will predict its value according to the timer timeout threads. During the data channel, rv_timer scoreboard will compare the read data with expected data in RAL.
Interrupt pins are checked against expected at every read/write data channel.
- TLUL assertions: The
tlul_assertassertions 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/rv_timer/dv/rv_timer_sim_cfg.hjson -i rv_timer_smoke
RV_TIMER random test performs following steps for number of iterations
Verify the reset values as indicated in the RAL specification.
Verify accessibility of CSRs as indicated in the RAL specification.
Verify no aliasing within individual bits of a CSR.
Verify no aliasing within the CSR address space.
Verify random reset during CSR/memory access.
This test is to exercise on the fly reset(timer is active)
This test to verify no activity in mTime, Interrupt Status, Interrupt signal, When all timers are deactive (ctrl.active = 0).
This test will verify update timer configuration on running timer.
This test will update timer value and compare value just before timer is going to expire (multiple times) and verify no interrupt is asserted
Do combinations of multiple of above scenarios to get multiple interrupts asserted at the same time. Scoreboard should be robust enough to deal with all scenarios.
Verify common intr_test CSRs that allows SW to mock-inject interrupts.
This test runs 3 parallel threads - stress_all, tl_errors and random reset. After reset is asserted, the test will read and check all valid CSR registers.
Access out of bounds address and verify correctness of response / behavior
Drive unsupported requests via TL interface and verify correctness of response / behavior. Below error cases are tested
Drive back-to-back requests without waiting for response to ensure there is one transaction outstanding within the TL device. Also, verify one outstanding when back- to-back accesses are made to the same address.
Access CSR with one or more bytes of data For read, expect to return all word value of the CSR For write, enabling bytes should cover all CSR valid fields