Add task to induce IBC droop

app/gimlet/dev.toml

@@ -13,6 +13,13 @@ task-slots = ["net"]
 features = ["vlan"]
 notifications = ["socket"]
 
+[tasks.drooper]
+name = "drooper"
+start = true
+priority = 6
+task-slots = ["i2c_driver"]
+notifications = ["timer"]
+
 [config.net.sockets.rpc]
 kind = "udp"
 owner = {name = "udprpc", notification = "socket"}

drv/i2c-devices/src/bmr491.rs

@@ -84,6 +84,13 @@ impl Bmr491 {
         })
     }
 
+    pub fn set_vout(&self, v: u16) -> Result<(), Error> {
+        let mut vout = VOUT_COMMAND::CommandData(0);
+        let value = Volts(v as f32);
+        vout.set(self.read_mode()?, pmbus::units::Volts(value.0))?;
+        pmbus_write!(self.device, VOUT_COMMAND, vout)
+    }
+
     pub fn read_vout(&self) -> Result<Volts, Error> {
         let vout = pmbus_read!(self.device, bmr491::READ_VOUT)?;
         Ok(Volts(vout.get(self.read_mode()?)?.0))

idl/drooper.idol

@@ -0,0 +1,14 @@
+// Interface to the task to droop the IBC voltage.
+Interface(
+    name: "Drooper",
+    ops: {
+        "droop": (
+            doc: "Droop the 12V rails for a given ms time period.",
+            args: {
+                "time_ms": "u64",
+            },
+            reply: Simple("()"),
+            idempotent: true,
+        ),
+    }
+)

task/drooper/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "drooper"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+idol-runtime.workspace = true
+num-traits.workspace = true
+userlib = { path = "../../sys/userlib", features = ["panic-messages"] }
+zerocopy.workspace = true
+zerocopy-derive.workspace = true
+
+drv-i2c-devices = { path = "../../drv/i2c-devices" }
+drv-i2c-api = { path = "../../drv/i2c-api" }
+
+[build-dependencies]
+idol.workspace = true
+
+build-i2c = { path = "../../build/i2c" }
+
+# This section is here to discourage RLS/rust-analyzer from doing test builds,
+# since test builds don't work for cross compilation.
+[[bin]]
+name = "drooper"
+test = false
+doctest = false
+bench = false
+
+[lints]
+workspace = true

task/drooper/build.rs

@@ -0,0 +1,18 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    idol::Generator::new()
+        .with_counters(
+            idol::CounterSettings::default().with_server_counters(false),
+        )
+        .build_server_support(
+            "../../idl/drooper.idol",
+            "server_stub.rs",
+            idol::server::ServerStyle::InOrder,
+        )?;
+
+    build_i2c::codegen(build_i2c::Disposition::Devices)?;
+    Ok(())
+}

task/drooper/src/main.rs

@@ -0,0 +1,63 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//!
+//! drooper: A task to simulate the IBC droop seen in mfg-quality#140
+//!
+//! Running this task will cause all U.2s to undergo a PCIe reset event.
+//! (Use with caution!)
+//!
+//! For example, to drop the voltage for 30 ms:
+//! $ humility hiffy -c drooper.droop -a time_ms=30
+//!
+
+#![no_std]
+#![no_main]
+
+use drv_i2c_devices::bmr491::*;
+
+use core::convert::Infallible;
+use idol_runtime::RequestError;
+use userlib::{task_slot, RecvMessage, UnwrapLite};
+
+task_slot!(I2C, i2c_driver);
+
+#[export_name = "main"]
+fn main() -> ! {
+    let mut server = ServerImpl {};
+    let mut buffer = [0; idl::INCOMING_SIZE];
+
+    loop {
+        idol_runtime::dispatch(&mut buffer, &mut server);
+    }
+}
+
+struct ServerImpl {}
+
+impl idl::InOrderDrooperImpl for ServerImpl {
+    fn droop(
+        &mut self,
+        _msg: &RecvMessage,
+        time_ms: u32,
+    ) -> Result<(), RequestError<Infallible>> {
+        let (device, rail) = i2c_config::pmbus::v12_sys_a2(I2C.get_task_id());
+        let ibc = Bmr491::new(&device, rail);
+
+        // Droop the voltage for the requested time period in ms.
+        // We pick 9V because it's approximately what we see in the field for mfg-quality#140.
+        let _ = ibc.set_vout(9);
+        userlib::hl::sleep_for(time_ms as u64);
+
+        // Restore to 12V.
+        let _ = ibc.set_vout(12);
+
+        Ok(())
+    }
+}
+
+mod idl {
+    include!(concat!(env!("OUT_DIR"), "/server_stub.rs"));
+}
+
+include!(concat!(env!("OUT_DIR"), "/i2c_config.rs"));