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minibar: make power button PC-like #423

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merged 1 commit into from
Oct 15, 2025
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minibar: make power button PC-like #423

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24 changes: 17 additions & 7 deletions hdl/projects/minibar/MinibarMiscRegs.bsv
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Original file line number Diff line number Diff line change
Expand Up @@ -70,8 +70,15 @@ module mkMinibarMiscRegs #(Integer pg_timeout_ms) (MinibarMiscRegs);
Reg#(PowerCtrl) power_control <- mkReg(defaultValue);
Reg#(SwitchResetCtrl) switch_reset_ctrl <- mkReg(defaultValue);

// Apply a 100ms debouncer to the button presses
Debouncer#(100, 100, Bit#(1)) power_button <- mkDebouncer(0);
// The intention behind the power button is for it to provide a normal PC-like behavior. When
// power is disabled, a short press can turn power on. We define this as 100ms just to get some
// debouncing applied. When power is enabled, a user must intentionally press and hold the
// button for a longer period (2000ms) to get the system to disable power.
Wire#(Bit#(1)) power_button_raw <- mkDWire(0);
Debouncer#(100, 100, Bit#(1)) power_button_short <- mkDebouncer(0);
Debouncer#(2000, 2000, Bit#(1)) power_button_long <- mkDebouncer(0);
mkConnection(power_button_short._write, power_button_raw._read);
mkConnection(power_button_long._write, power_button_raw._read);

// VBUS rail under FPGA control
PowerRail#(10) vbus_rail <- mkPowerRailDisableOnAbort(pg_timeout_ms);
Expand All @@ -82,16 +89,19 @@ module mkMinibarMiscRegs #(Integer pg_timeout_ms) (MinibarMiscRegs);
(* fire_when_enabled *)
rule do_tick (tick);
vbus_rail.send();
power_button.send();
power_button_short.send();
power_button_long.send();
endrule

(* fire_when_enabled *)
rule do_power_control;
let toggle_power = power_button.rising_edge();
let sw_enable = new_sw_vbus_en && power_control.vbus_sled_en == 1;
let sw_disable = new_sw_vbus_en && power_control.vbus_sled_en == 0;
let disable_power = sw_disable || vbus_rail.timed_out() || vbus_rail.aborted() || (toggle_power && vbus_en_r);
let enable_power = !vbus_en_r && (sw_enable || toggle_power);
let disable_power = sw_disable ||
vbus_rail.timed_out() ||
vbus_rail.aborted() ||
(power_button_long.rising_edge() && vbus_en_r);
let enable_power = !vbus_en_r && (sw_enable || power_button_short.rising_edge());

if (enable_power) begin
vbus_rail.set_enable(True);
Expand All @@ -115,7 +125,7 @@ module mkMinibarMiscRegs #(Integer pg_timeout_ms) (MinibarMiscRegs);
interface Pins pins;
method vbus_sys_fault = vbus_sys_fault_r._write;
method hcv_code = hcv_code_r._write;
method power_button = power_button._write;
method power_button = power_button_raw._write;
method pcie_con_present = pcie_con_present._write;
method rsw0_con_present = rsw0_con_present._write;
method rsw1_con_present = rsw1_con_present._write;
Expand Down