PWRMGR DV document

Goals

• DV
  • Verify all PWRMGR 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
  • HW development stages
• Simulation results

Design features

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

Testbench architecture

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

Block diagram

Top level testbench

Top level testbench is located at hw/ip/pwrmgr/dv/tb.sv. It instantiates the PWRMGR DUT module hw/ip/pwrmgr/rtl/pwrmgr.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
• PWRMGR interface hw/ip/pwrmgr/dv/env/pwrmgr_if.sv.
• Interrupts (pins_if)
• Alerts (alert_esc_if)
• Devmode (pins_if)

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 pwrmgr_env_pkg. Some of them in use are:

  typedef enum int {
    WakeupSysrst,
    WakeupDbgCable,
    WakeupPin,
    WakeupUsb,
    WakeupAonTimer,
    WakeupSensorCtrl
  } wakeup_e;

  typedef struct packed {
    logic main_pd_n;
    logic usb_clk_en_active;
    logic usb_clk_en_lp;
    logic io_clk_en;
    logic core_clk_en;
  } control_enables_t;

  typedef bit [pwrmgr_reg_pkg::NumWkups-1:0] wakeups_t;
  typedef bit [pwrmgr_reg_pkg::NumRstReqs-1:0] resets_t;

  // This is used to send all resets to rstmgr.
  typedef bit [pwrmgr_pkg::HwResetWidth-1:0] resets_out_t;

TL_agent

PWRMGR 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 PWRMGR device.

UVM RAL Model

The PWRMGR 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

The sequences are closely related to the testplan’s testpoints. Testpoints and coverage are described in more detail in the testplan. All test sequences reside in hw/ip/pwrmgr/dv/env/seq_lib, and extend pwrmgr_base_vseq. The pwrmgr_base_vseq virtual sequence is extended from cip_base_vseq and serves as a starting point. It provides commonly used handles, variables, functions and tasks used by the test sequences. Some of the most commonly used tasks and functions are as follows:

• task wait_for_fast_fsm_active: Waits for the fetch_en_o output to become 1, indicating the fast fsm is active and the CPU can fetch instructions. We wait for this before the tests can start, since any CSR accesses require the CPU to be running. Due to complexities in the UVM sequences this task is called in the virtual post_apply_reset task of dv_base_vseq.
• task wait_for_csr_to_propagate_to_slow_domain: Waits for cfg_cdc_sync CSR to be clear, indicating the CDC to the slow clock has completed.
• task wait_for_reset_cause: Waits for the pwr_rst_req.reset_cause output to match an expected cause.
• task check_wait_info: Checks the wake_info CSR matches expectations.
• task check_reset_status: Checks the reset_status CSR matches expectations.
• task check_and_clear_interrupt: Checks the interrupt enable, status, and output pin.

In addition, the base sequence provides two tasks that provide expected inputs based on the pwrmgr outputs. In the absence of these inputs the pwrmgr will be stuck waiting forever. Being based on outputs means the inputs are in accordance to the implicit protocol. The tasks in question are:

• task slow_responder: Handles required input changes from AST for the slow state machine. For the various <clk>_en outputs it changes the <clk>_val as required, for core, io, main, and usb clocks.
• task fast_responder: Handles input changes for the fast state machine.
  • Completes the handshake with rstmgr for lc and sys resets: some random cycles after an output reset is requested the corresponding reset src input must go low.
  • Completes the handshake with clkmgr: the various <clk>_status inputs need to match the corresponding <clk>_ip_clk_en output after some cycles, for io, main, and usb clocks.
  • Completes the handshake with lc and otp: both *_done inputs must match the corresponding *_init outputs after some cycles.

These tasks are started by the parent sequence’s pre_start task, and terminated gracefully in the parent sequence’s post_start task.

Test sequences

The test sequences besides the base are as follows:

• pwrmgr_smoke_vseq tests the pwrmgr through POR, entry and exit from software initiated low power and reset.
• pwrmgr_wakeup_vseq checks the transitions to low power and the wakeup settings. It randomizes wakeup inputs, wakeup enables, the wakeup info capture enable, and the interrupt enable.
• pwrmgr_aborted_low_power_vseq creates scenarios that lead to aborting a low power transition. The abort can be due to the processor waking up very soon, or otp, lc, or flash being busy.
• pwrmgr_reset_vseq checks the pwrmgr response to conditional resets and reset enables, and unconditional escalation and main power glitch resets.
• pwrmgr_wakeup_reset_vseq aligns reset and wakeup from low power.
• pwrmgr_lowpower_wakeup_race_vseq aligns a wakeup event coming in proximity to low power entry. Notice the wakeup is not expected to impact low power entry, since it is not sampled at this time.

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:

• wakeup_ctrl_cg covers wakeup and capture control.
• wakeup_intr_cg covers control of the interrupt due to a wakeup.
• control_cg covers clock controls.
• hw_reset_0_cg covers external reset via rstreqs_i[0].
• hw_reset_1_cg covers external reset via rstreqs_i[1].
• rstmgr_sw_reset_cg covers software initiated resets via rstmgr CSR.
• main_power_reset_cg covers resets due to a main power glitch.
• esc_reset_cg covers resets due to an incoming escalation.
• reset_wakeup_distance_cg covers the distance in clock cycles between a wakeup and a reset request.

More details about these sequences and covergroups can be found at testplan.

Self-checking strategy

Many of the checks are performed via SVA, and are enabled for all test sequences. Refer to the assertions section below for details.

Scoreboard

The pwrmgr_scoreboard is primarily used for end to end checking.

Many inputs must have specific transitions to prevent the pwrmgr fsms from wait forever. When possible the transitions are triggered by pwrmgr output changes. These are described according to the unit that originates or is the recipient of the ports. See also the test plan for specific ways these are driven to trigger different testpoints.

AST

• Output slow_clk_en is always on.
• Input slow_clk_val is unused.
• Outputs core_clk_en, io_clk_en, and usb_clk_en reset low, and go high prior to the slow fsm requesting the fast fsm to wakeup. Notice the usb clock can be programmed to stay low on wakeup via the control CSR. These clock enables are cleared on reset, and should match their corresponding enables in the control CSR on low power transitions. These clock enables are checked via SVAs in hw/ip/pwrmgr/dv/sva/pwrmgr_clock_enables_sva_if.sv. When slow fsm transitions to SlowPwrStateReqPwrUp the clock enables should be on (except usb should match control.usb_clk_en_active). When slow fsm transitions to SlowPwrStatePwrClampOn the clock enables should match their bits in the control CSR.
• Inputs core_clk_val, io_clk_val, and usb_clk_val track the corresponding enables. They are driven by slow_responder, which turn them off when their enables go off, and turn them back on a few random slow clock cycles after their enables go on. Slow fsm waits for them to go high prior to requesting fast fsm wakeup. Lack of a high transition when needed is detected via timeout. Such timeout would be due to the corresponding enables being set incorrectly. These inputs are checked via SVAs in hw/ip/pwrmgr/dv/sva/pwrmgr_ast_sva_if.sv.
• Output main_pd_n should go high when slow fsm transitions to SlowPwrStateMainPowerOn, and should match control.main_pd_n CSR when slow fsm transitions to SlowPwrStateMainPowerOff.
• Input main_pok should turn on for the slow fsm to start power up sequence. This is also driven by slow_responder, which turn this off in response to main_pd_n going low, and turn it back on after a few random slow clock cycles from main_pd_n going high. Lack of a high transition causes a timeout, and would point to main_pd_n being set incorrectly.
• Output transitions of pwr_clamp_env must always precede transitions of pwr_clamp output. Output transitions of pwr_clamp to active must always precede transitions of main_pd_n output to active. Output transitions of pwr_clamp to inactive must always follow transitions of main_pd_n output to inactive.

RSTMGR

• Output rst_lc_req resets to 1, also set on reset transition, and on low power transitions that turn off main clock. Cleared early on during the steps to fast fsm active.
• Input rst_lc_src_n go low in response to rst_lc_req high, go high when rst_lc_req clears (and lc is reset). Driven by fast_responder in response to rst_lc_req, waiting a few random cycles prior to transitions. Fast fsm waits for it to go low before deactivating, and for it to go high before activating. Checked implicitly by lack of timeout: a timeout would be due to rst_lc_req being set incorrectly, and by SVA as described below.
• Output rst_sys_req resets to 1, also set to on reset, and on low power transitions that turn off main clock. Cleared right before the fast fsm goes active.
• Input rst_sys_src_n go low in response to rst_sys_req high. Transitions go high when rst_sysd_req clears (and lc is reset). Fast fsm waits for it to go low before deactivating. Also driver by fast_responder. Checked implicitly by lack of timeout, and by SVA.
• Output rstreqs correspond to the enabled pwrmgr rstreqs inputs plus main power glitch, escalation reset, and software reset request from RSTMGR. Checked in scoreboard and SVA.
• Output reset_cause indicates a reset is due to low power entry or a reset request. Checked in scoreboard.

CLKMGR

• Outputs pwr_clk_o.<clk>_ip_clk_en reset low, are driven high by fast fsm when going active, and driven low when going inactive. The <clk> correspond to io, main, and usb.
• Inputs pwr_clk_i.<clk>_status are expected to track pwr_clk_o.<clk>_ip_clk_en. Fast fsm waits for them going high prior to going active, and going low prior to deactivating. These are controlled by the control CSR. Driven by fast_responder, which turns them off when <clk>_ip_clk_en goes low, and turns them back on a few random cycles after <clk>_ip_clk_en goes high. Checked by lack of a timeout: such timeout would be due to ip_clk_en being set incorrectly. Also checked by SVA.

OTP

• Output otp_init resets low, goes high when the fast fsm is going active, and low after the otp_done input goes high.
• Input otp_done is driven by fast_responder. It is initialized low, and goes high some random cycles after otp_init goes high. The sequencer will timeout if otp_init is not driven high.
• Input otp_idle normally set high, but is set low by the pwrmgr_aborted_low_power_vseq sequence.

LC

The pins connecting to LC behave pretty much the same way as those to OTP.

FLASH

• Input flash_idle is handled much like lc_idle and otp_idle.

CPU

• Input core_sleeping is driven by sequences. It is driven low to enable a transition to low power. After the transition is under way it is a don’t care. The pwrmgr_aborted_low_power_vseq sequence sets it carefully to abort a low power entry soon after the attempt because the processor wakes up.

Wakeups and Resets

There are a number of wakeup and reset requests. They are driven by sequences as they need to.

Assertions

The hw/ip/pwrmgr/dv/sva/pwrmgr_bind.sv module binds a few modules containing assertions to the IP as follows:

• TLUL assertions: the tlul_assert assertions ensures TileLink interface protocol compliance.
• Clock enables assertions: The pwrmgr_clock_enables_sva_if module contains assertions checking that the various clk_en outputs correspond to the settings in the control CSR.
• CLKMGR clk_en to status handshake assertions: The clkmgr_pwrmgr_sva_if contains assertions checking the various <clk>_status inputs track the corresponding <clk>_ip_clk_en outputs.
• AST input/output handshake assertions: The pwrmgr_ast_sva_if module contains assertions checking that the inputs from the AST respond to the pwrmgr outputs.
• RSTMGR input/output handshake assertions: The pwrmgr_rstmgr_sva_if module contains assertions checking the following:
  • The rst_lc_src_n input from RSTMGR respond to the rst_lc_req pwrmgr output.
  • The rst_sys_src_n input from RSTMGR respond to the rst_sys_req pwrmgr output.
  • The different pwr_rst_o.rstreqs output bits track the corresponding reset causes. These include hardware, power glitch, escalation, and software resets.

In addition, 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/pwrmgr/dv/pwrmgr_sim_cfg.hjson -i pwrmgr_smoke

Testplan

Testplan