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[entropy_src/dv] Separate external health test (XHT) verification from V2 tests #17638

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merged 4 commits into from
Mar 24, 2023
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[entropy_src/dv] Separate external health test (XHT) verification from V2 tests #17638

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0c30e16
[entropy_src/dv] Add knob to keep default XHT rsp
andreaskurth Mar 21, 2023
a62d494
[entropy_src/dv] Check default XHT rsp if enabled
andreaskurth Mar 21, 2023
2e7e815
[entropy_src/dv] Create separate test for RNG with XHT rsp
andreaskurth Mar 21, 2023
ec3e4b2
[entropy_src,dv] Add testpoint for external health tests
andreaskurth Mar 22, 2023
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9 changes: 9 additions & 0 deletions hw/ip/entropy_src/data/entropy_src_testplan.hjson
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Expand Up @@ -118,6 +118,15 @@
stage: V2
tests: ["entropy_src_functional_errors"]
}
{
name: external_health_tests
desc: '''
Verify the external health test (XHT) interface and functionality, including continuous
and windowed functionality and different high/low thresholds and watermarks.
'''
stage: V3
tests: ["entropy_src_rng_with_xht_rsps"], // TODO(#16276): Complete XHT verification
}
]
covergroups: [
{
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7 changes: 7 additions & 0 deletions hw/ip/entropy_src/dv/entropy_src_sim_cfg.hjson
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Expand Up @@ -73,6 +73,13 @@
uvm_test_seq: entropy_src_rng_vseq
}

{
name: entropy_src_rng_with_xht_rsps
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NB: This test has the default number of reseeds (50), whereas entropy_src_rng still has 300. The number of reseeds can be increased later depending on XHT coverage (#16276)

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Sounds good.

uvm_test: entropy_src_rng_test
uvm_test_seq: entropy_src_rng_vseq
run_opts: ["+xht_only_default_rsp=0"]
}

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{
name: entropy_src_stress_all
uvm_test: entropy_src_stress_all_test
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3 changes: 3 additions & 0 deletions hw/ip/entropy_src/dv/env/entropy_src_env_cfg.sv
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Expand Up @@ -112,6 +112,9 @@ class entropy_src_env_cfg extends cip_base_env_cfg #(.RAL_T(entropy_src_reg_bloc
// alert within alert_max_delay clock cycles.
int alert_max_delay;

// Whether to keep the default response on the XHT interface at all time.
bit xht_only_default_rsp = 1;

///////////////////////
// Randomized fields //
///////////////////////
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16 changes: 16 additions & 0 deletions hw/ip/entropy_src/dv/env/entropy_src_scoreboard.sv
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Expand Up @@ -183,6 +183,7 @@ class entropy_src_scoreboard extends cip_base_scoreboard#(
process_interrupts();
process_fifo_exceptions();
health_test_scoring_thread();
process_xht();
join_none
end
endtask
Expand Down Expand Up @@ -1107,6 +1108,21 @@ class entropy_src_scoreboard extends cip_base_scoreboard#(
end
endtask

task process_xht();
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Great idea to add such a check!

Nit: should this task rather be named check_xht_response()?

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@andreaskurth andreaskurth Mar 22, 2023 •
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Yeah, at some point the scoreboard will have to take XHT transactions into account for its modeling and checking, as it already does for TL accesses, for example. By convention, these tasks seem to start with process_, e.g., process_tl_access is defined for our scoreboards derived from cip_base_scoreboard. So I think process_xht is appropriate.

Note that in a proper UVM design, the scoreboard would not sample I/Os directly but use TLM analysis FIFOs (again using the TL example, the scoreboard calls process_tl_fifo -> process_tl_a_item -> process_tl_access). I decided against this design for now for two main reasons:

  • It's overly complicated for the check we need right now.
  • As we want to ensure the DUT sees a fixed value in every cycle, directly sampling I/O is less error-prone than the indirection through a monitor and analysis FIFOs.

When implementing XHT tests, the checks in this PR can be complemented by or moved to TLM-based checks.

// Process XHT transactions.
forever begin
@(cfg.m_xht_agent_cfg.vif.mon_cb);
if (cfg.under_reset) continue;

if (cfg.xht_only_default_rsp) begin
// If the environment is configured to maintain the default XHT response at all time, ensure
// that this is really the case.
`DV_CHECK_EQ(cfg.m_xht_agent_cfg.vif.mon_cb.rsp,
entropy_src_pkg::ENTROPY_SRC_XHT_RSP_DEFAULT)
end
end
endtask

// All the HT threshold registers are one-way: they can only become more strict unless
// the DUT is reset. This function encapsulates this behavior.
//
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4 changes: 3 additions & 1 deletion hw/ip/entropy_src/dv/env/seq_lib/entropy_src_rng_vseq.sv
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Expand Up @@ -425,7 +425,9 @@ class entropy_src_rng_vseq extends entropy_src_base_vseq;
fork
m_rng_push_seq.start(p_sequencer.rng_sequencer_h);
m_csrng_pull_seq.start(p_sequencer.csrng_sequencer_h);
m_xht_seq.start(p_sequencer.xht_sequencer);
if (!cfg.xht_only_default_rsp) begin
m_xht_seq.start(p_sequencer.xht_sequencer);
end
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join_none
endtask

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7 changes: 7 additions & 0 deletions hw/ip/entropy_src/dv/tests/entropy_src_base_test.sv
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Expand Up @@ -27,6 +27,13 @@ class entropy_src_base_test extends cip_base_test #(
// Overrides should happen in the specific testcase.

virtual function void configure_env();
// Take plusargs into account.
bit xht_only_default_rsp;
if ($value$plusargs("xht_only_default_rsp=%0b", xht_only_default_rsp)) begin
`uvm_info(`gfn, $sformatf("+xht_only_default_rsp specified"), UVM_MEDIUM)
cfg.xht_only_default_rsp = xht_only_default_rsp;
end

// seed_cnt only used by smoke test
// so there is no need to randomize it.
cfg.seed_cnt = 1;
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