ALERT_HANDLER DV document

Goals

• DV
  • Verify all ALERT_HANDLER 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
  • Verify transmitter and receiver pairs for alert (/hw/ip/prim/dv/prim_alert) and escalation (/hw/ip/prim/dv/prim_esc) via direct stimulus.
• FPV
  • Verify TileLink device protocol compliance with an SVA based testbench
  • Verify transmitter and receiver pairs for alert and escalator
  • Verify alert_handler_esc_timer and alert_handler_ping_timer

Current status

• Design & verification stage
  • HW development stages
• Simulation results

Design features

For detailed information on ALERT_HANDLER design features, please see the ALERT_HANDLER HWIP technical specification.

Testbench architecture

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

Block diagram

Top level testbench

Top level testbench is located at hw/ip/alert_handler/dv/tb/tb.sv. It instantiates the ALERT_HANDLER DUT module hw/ip/alert_handler/rtl/alert_handler.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
• TileLink host interface
• ALERT_HANDLER IOs
• Alerts and escalations(alert_esc_if)
• Interrupts (pins_if)

The alert_handler testbench environment can be reused in chip level testing.

Common DV utility components

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

• dv_utils_pkg
• csr_utils_pkg

Global types & methods

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

  parameter uint NUM_MAX_ESC_SEV = 8;

TL_agent

ALERT_HANDLER 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 ALERT_HANDLER device.

ALERT_ESC Agent

ALERT_ESC agent is used to drive and monitor transmitter and receiver pairs for the alerts and escalators. Alert_handler DUT includes alert_receivers and esc_senders, so the alert_esc agent will drive output signals of the alert_senders and esc_receivers.

UVM RAL Model

The ALERT_HANDLER 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/alert_handler/dv/env/seq_lib. The alert_handler_base_vseq virtual sequence is extended from cip_base_vseq and serves as a starting point. All test sequences are extended from alert_handler_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:

• alert_handler_init: Configure alert_handler DUT by writing to intr_en, alert_en_shadowed_*, alert_class_shadowed_*, loc_alert_en_shadowed_*, loc_alert_class_shadowed_* registers.
• drive_alert: Drive alert_tx signal pairs through alert_sender_driver.
• drive_esc_rsp: Drive esc_rx signal pairs through esc_receiver_driver.
• read_ecs_status: Readout registers that reflect escalation status, including classa/b/c/d_accum_cnt, classa/b/c/d_esc_cnt, and classa/b/c/d_state.
• wait_alert_handshake_done: Wait for alert_rx/tx handshake to finish. If the alert’s low-power-group(LPG) is enabled, immediately return.
• wait_esc_handshake_done: Wait for esc_rx/tx handshake to finish by reading class*_state registers and check esc_rx/tx signals.
• set_alert_lpg: Given alert index, find the linked LPG group and enabled the LPG group by driving lpg_cg_en or lpg_rst_en to Mubi4True.
• run_esc_rsp_seq_nonblocking: A non-blocking sequence to drive esc_tx when received escalation or escalation-ping requests.
• run_alert_ping_rsp_seq_nonblocking: A non-blocking sequence to drive alert_rx when received alert-ping requests.

Functional coverage

To ensure high quality constrained random stimulus, it is necessary to develop a functional coverage model. The detailed covergroups are documented under alert_handler testplan.

Self-checking strategy

Scoreboard

The alert_handler_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
• alert_fifo: An array of alert_fifo that connects to corresponding alert_monitors
• esc_fifo: An array of esc_fifo that connects to corresponding esc_monitors

Alert_handler scoreboard monitors all valid CSR registers, alert handshakes, and escalation handshakes. To ensure certain alert, interrupt, or escalation signals are triggered at the expected time, the alert_handler scoreboard implemented a few counters:

• intr_cnter_per_class[NUM_ALERT_HANDLER_CLASSES]: Count number of clock cycles that the interrupt bit stays high. If the stored number is larger than the timeout_cyc registers, the corresponding escalation is expected to be triggered
• accum_cnter_per_class[NUM_ALERT_HANDLER_CLASSES]: Count number of alerts triggered under the same class. If the stored number is larger than the accum_threshold registers, the corresponding escalation is expected to be triggered
• esc_cnter_per_signal[NUM_ESC_SIGNALS]: Count number of clock cycles that each escalation signal stays high. Compare the counter against phase_cyc registers

The alert_handler scoreboard is parameterized to support different number of classes, alert pairs, and escalation pairs.

Assertions

• TLUL assertions: The tb/alert_handler_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 $REPO_TOP/hw/$CHIP/ip_autogen/alert_handler/dv/alert_handler_sim_cfg.hjson -i alert_handler_smoke

In this run command, $CHIP can be top_earlgrey, etc.

Testplan

Testplan