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[prim,fpv] Waive impossible cover items from async alert fpv #29632

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[prim,fpv] Waive impossible cover items from async alert fpv #29632

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49 changes: 49 additions & 0 deletions hw/ip/prim/fpv/tb/rxtx_after_load.tcl
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,39 @@ proc move_to_task {task_name assert_name} {
assert -disable ${assert_name}
}

# Explicitly waive coverage for the empty default item at the end of the case statement in some
# instance of prim_diff_decode. This item doesn't actually have any effect, but is recommended by
# our style guide because in some situations this sort of thing affects behaviour when the FSM state
# is 'x.
proc waive_end_of_decode_fsm {instance} {
# Get a list of all the cover items that depend on state_q (the FSM state) as a fanin
set names [check_cov -name -get_cover_id -source ${instance}.state_q -direction fanin]

# The cover item we are looking for has a name that starts with
# ${instance}.gen_async.p_diff_fsm._automatic_. The item has subtype "case_stmt_empty_branch"
# and it should be the only on with that subtype. Filter for items with the subtype.
set regex "${instance}\\.gen_async\\.p_diff_fsm\\._automatic_.*case_stmt_empty_branch"
set filtered [lsearch -all -inline -regexp $names $regex]

# There should be exactly one hit
set num_hits [llength ${filtered}]
if {${num_hits} != 1} {
error "# hits for empty case at end of ${instance} FSM: ${num_hits}, but we expected 1."
}

# Convert the cover item name back to an id. Bizarrely, the result with a silly name is
# (uint32_t)(-1). To check nothing crazy has happened, check that the result is less than
# 10,000.
set cov_id [check_cov -get_cover_id -cover_name ${filtered}]
if {${cov_id} > 10000} {
error "Failed to find cover id for ${filtered}"
}

# Finally, waive the cover item
puts "Waiving coverage for empty case item at end of FSM in ${instance}."
check_cov -waiver -add -cover_item_id ${cov_id} -comment "Empty case item at end of FSM"
}


set valid_state_props [get_property_list -regexp -include {"name" "ValidState_A$"}]
foreach prop $valid_state_props {
Expand All @@ -34,3 +67,19 @@ foreach psn $parasitic_state_props {
# Add FreeFsm to the cov_tasks variable, which is a list of the tasks that will be used for
# check_cov at the end of fpv.tcl if coverage is enabled.
lappend cov_tasks FreeFsm

# If the alert sender/receiver pair is asynchronous then we want to waive the do-nothing empty case
# item at the end of each instance of prim_diff_decode. We detect this by looking at an "AsyncOn"
# localparam in the top module.
set localparams [get_design_info -list local_parameter -verbosity silent]
set async_on "?"
foreach {k v} ${localparams} {
if {[string equal ${k} "AsyncOn"]} { set async_on $v; }
}
if {${async_on} == "?"} { error "No AsyncOn localparam in tb"; }

if {${async_on} == "1'b1"} {
waive_end_of_decode_fsm i_prim_alert_sender.u_decode_ping
waive_end_of_decode_fsm i_prim_alert_sender.u_decode_ack
waive_end_of_decode_fsm i_prim_alert_receiver.u_decode_alert
}
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