[PATCH v4 5/5] gpu: nova-core: gsp: add mutex locking to Cmdq

[Eliot Courtney <ecourtney@nvidia.com>]

Wrap `Cmdq`'s mutable state in a new struct `CmdqInner` and wrap that in
a Mutex. This lets `Cmdq` methods take &self instead of &mut self, which
lets required commands be sent e.g. while unloading the driver.

The mutex is held over both send and receive in `send_command` to make
sure that it doesn't get the reply of some other command that could have
been sent just beforehand.

Reviewed-by: Zhi Wang <zhiw@nvidia.com>
Tested-by: Zhi Wang <zhiw@nvidia.com>
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/boot.rs      |   8 +-
 drivers/gpu/nova-core/gsp/cmdq.rs      | 165 ++++++++++++++++++++-------------
 drivers/gpu/nova-core/gsp/commands.rs  |   4 +-
 drivers/gpu/nova-core/gsp/sequencer.rs |   2 +-
 4 files changed, 105 insertions(+), 74 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/boot.rs b/drivers/gpu/nova-core/gsp/boot.rs
index 991eb5957e3d..bc53e667cd9e 100644
--- a/drivers/gpu/nova-core/gsp/boot.rs
+++ b/drivers/gpu/nova-core/gsp/boot.rs
@@ -128,7 +128,7 @@ fn run_fwsec_frts(
     ///
     /// Upon return, the GSP is up and running, and its runtime object given as return value.
     pub(crate) fn boot(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         pdev: &pci::Device<device::Bound>,
         bar: &Bar0,
         chipset: Chipset,
@@ -214,13 +214,13 @@ pub(crate) fn boot(
             dev: pdev.as_ref().into(),
             bar,
         };
-        GspSequencer::run(&mut self.cmdq, seq_params)?;
+        GspSequencer::run(&self.cmdq, seq_params)?;
 
         // Wait until GSP is fully initialized.
-        commands::wait_gsp_init_done(&mut self.cmdq)?;
+        commands::wait_gsp_init_done(&self.cmdq)?;
 
         // Obtain and display basic GPU information.
-        let info = commands::get_gsp_info(&mut self.cmdq, bar)?;
+        let info = commands::get_gsp_info(&self.cmdq, bar)?;
         match info.gpu_name() {
             Ok(name) => dev_info!(pdev, "GPU name: {}\n", name),
             Err(e) => dev_warn!(pdev, "GPU name unavailable: {:?}\n", e),
diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 90179256a929..47406d494523 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -18,8 +18,12 @@
     },
     dma_write,
     io::poll::read_poll_timeout,
+    new_mutex,
     prelude::*,
-    sync::aref::ARef,
+    sync::{
+        aref::ARef,
+        Mutex, //
+    },
     time::Delta,
     transmute::{
         AsBytes,
@@ -477,12 +481,9 @@ struct GspMessage<'a> {
 /// area.
 #[pin_data]
 pub(crate) struct Cmdq {
-    /// Device this command queue belongs to.
-    dev: ARef<device::Device>,
-    /// Current command sequence number.
-    seq: u32,
-    /// Memory area shared with the GSP for communicating commands and messages.
-    gsp_mem: DmaGspMem,
+    /// Inner mutex-protected state.
+    #[pin]
+    inner: Mutex<CmdqInner>,
 }
 
 impl Cmdq {
@@ -502,18 +503,17 @@ impl Cmdq {
     /// Number of page table entries for the GSP shared region.
     pub(crate) const NUM_PTES: usize = size_of::<GspMem>() >> GSP_PAGE_SHIFT;
 
-    /// Timeout for waiting for space on the command queue.
-    const ALLOCATE_TIMEOUT: Delta = Delta::from_secs(1);
-
     /// Default timeout for receiving a message from the GSP.
     pub(super) const RECEIVE_TIMEOUT: Delta = Delta::from_secs(5);
 
     /// Creates a new command queue for `dev`.
     pub(crate) fn new(dev: &device::Device<device::Bound>) -> impl PinInit<Self, Error> + '_ {
         try_pin_init!(Self {
-            gsp_mem: DmaGspMem::new(dev)?,
-            dev: dev.into(),
-            seq: 0,
+            inner <- new_mutex!(CmdqInner {
+                dev: dev.into(),
+                gsp_mem: DmaGspMem::new(dev)?,
+                seq: 0,
+            }),
         })
     }
 
@@ -537,6 +537,87 @@ fn notify_gsp(bar: &Bar0) {
             .write(bar);
     }
 
+    /// Sends `command` to the GSP and waits for the reply.
+    ///
+    /// The mutex is held for the entire send+receive cycle to ensure that no other command can
+    /// be interleaved. Messages with non-matching function codes are silently consumed until the
+    /// expected reply arrives.
+    ///
+    /// # Errors
+    ///
+    /// - `ETIMEDOUT` if space does not become available to send the command, or if the reply is
+    ///   not received within the timeout.
+    /// - `EIO` if the variable payload requested by the command has not been entirely
+    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
+    ///
+    /// Error codes returned by the command and reply initializers are propagated as-is.
+    pub(crate) fn send_command<M>(&self, bar: &Bar0, command: M) -> Result<M::Reply>
+    where
+        M: CommandToGsp,
+        M::Reply: MessageFromGsp,
+        Error: From<M::InitError>,
+        Error: From<<M::Reply as MessageFromGsp>::InitError>,
+    {
+        let mut inner = self.inner.lock();
+        inner.send_command(bar, command)?;
+
+        loop {
+            match inner.receive_msg::<M::Reply>(Self::RECEIVE_TIMEOUT) {
+                Ok(reply) => break Ok(reply),
+                Err(ERANGE) => continue,
+                Err(e) => break Err(e),
+            }
+        }
+    }
+
+    /// Sends `command` to the GSP without waiting for a reply.
+    ///
+    /// # Errors
+    ///
+    /// - `ETIMEDOUT` if space does not become available within the timeout.
+    /// - `EIO` if the variable payload requested by the command has not been entirely
+    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
+    ///
+    /// Error codes returned by the command initializers are propagated as-is.
+    pub(crate) fn send_command_no_wait<M>(&self, bar: &Bar0, command: M) -> Result
+    where
+        M: CommandToGsp<Reply = NoReply>,
+        Error: From<M::InitError>,
+    {
+        self.inner.lock().send_command(bar, command)
+    }
+
+    /// Receive a message from the GSP.
+    ///
+    /// See [`CmdqInner::receive_msg`] for details.
+    pub(crate) fn receive_msg<M: MessageFromGsp>(&self, timeout: Delta) -> Result<M>
+    where
+        // This allows all error types, including `Infallible`, to be used for `M::InitError`.
+        Error: From<M::InitError>,
+    {
+        self.inner.lock().receive_msg(timeout)
+    }
+
+    /// Returns the DMA handle of the command queue's shared memory region.
+    pub(crate) fn dma_handle(&self) -> DmaAddress {
+        self.inner.lock().gsp_mem.0.dma_handle()
+    }
+}
+
+/// Inner mutex protected state of [`Cmdq`].
+struct CmdqInner {
+    /// Device this command queue belongs to.
+    dev: ARef<device::Device>,
+    /// Current command sequence number.
+    seq: u32,
+    /// Memory area shared with the GSP for communicating commands and messages.
+    gsp_mem: DmaGspMem,
+}
+
+impl CmdqInner {
+    /// Timeout for waiting for space on the command queue.
+    const ALLOCATE_TIMEOUT: Delta = Delta::from_secs(1);
+
     /// Sends `command` to the GSP, without splitting it.
     ///
     /// # Errors
@@ -617,7 +698,7 @@ fn send_single_command<M>(&mut self, bar: &Bar0, command: M) -> Result
     ///   written to by its [`CommandToGsp::init_variable_payload`] method.
     ///
     /// Error codes returned by the command initializers are propagated as-is.
-    fn send_command_internal<M>(&mut self, bar: &Bar0, command: M) -> Result
+    fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
     where
         M: CommandToGsp,
         Error: From<M::InitError>,
@@ -637,51 +718,6 @@ fn send_command_internal<M>(&mut self, bar: &Bar0, command: M) -> Result
         }
     }
 
-    /// Sends `command` to the GSP and waits for the reply.
-    ///
-    /// # Errors
-    ///
-    /// - `ETIMEDOUT` if space does not become available to send the command, or if the reply is
-    ///   not received within the timeout.
-    /// - `EIO` if the variable payload requested by the command has not been entirely
-    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
-    ///
-    /// Error codes returned by the command and reply initializers are propagated as-is.
-    pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result<M::Reply>
-    where
-        M: CommandToGsp,
-        M::Reply: MessageFromGsp,
-        Error: From<M::InitError>,
-        Error: From<<M::Reply as MessageFromGsp>::InitError>,
-    {
-        self.send_command_internal(bar, command)?;
-
-        loop {
-            match self.receive_msg::<M::Reply>(Self::RECEIVE_TIMEOUT) {
-                Ok(reply) => break Ok(reply),
-                Err(ERANGE) => continue,
-                Err(e) => break Err(e),
-            }
-        }
-    }
-
-    /// Sends `command` to the GSP without waiting for a reply.
-    ///
-    /// # Errors
-    ///
-    /// - `ETIMEDOUT` if space does not become available within the timeout.
-    /// - `EIO` if the variable payload requested by the command has not been entirely
-    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
-    ///
-    /// Error codes returned by the command initializers are propagated as-is.
-    pub(crate) fn send_command_no_wait<M>(&mut self, bar: &Bar0, command: M) -> Result
-    where
-        M: CommandToGsp<Reply = NoReply>,
-        Error: From<M::InitError>,
-    {
-        self.send_command_internal(bar, command)
-    }
-
     /// Wait for a message to become available on the message queue.
     ///
     /// This works purely at the transport layer and does not interpret or validate the message
@@ -717,7 +753,7 @@ fn wait_for_msg(&self, timeout: Delta) -> Result<GspMessage<'_>> {
         let (header, slice_1) = GspMsgElement::from_bytes_prefix(slice_1).ok_or(EIO)?;
 
         dev_dbg!(
-            self.dev,
+            &self.dev,
             "GSP RPC: receive: seq# {}, function={:?}, length=0x{:x}\n",
             header.sequence(),
             header.function(),
@@ -752,7 +788,7 @@ fn wait_for_msg(&self, timeout: Delta) -> Result<GspMessage<'_>> {
         ])) != 0
         {
             dev_err!(
-                self.dev,
+                &self.dev,
                 "GSP RPC: receive: Call {} - bad checksum\n",
                 header.sequence()
             );
@@ -781,7 +817,7 @@ fn wait_for_msg(&self, timeout: Delta) -> Result<GspMessage<'_>> {
     /// - `ERANGE` if the message had a recognized but non-matching function code.
     ///
     /// Error codes returned by [`MessageFromGsp::read`] are propagated as-is.
-    pub(crate) fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Result<M>
+    fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Result<M>
     where
         // This allows all error types, including `Infallible`, to be used for `M::InitError`.
         Error: From<M::InitError>,
@@ -817,9 +853,4 @@ pub(crate) fn receive_msg<M: MessageFromGsp>(&mut self, timeout: Delta) -> Resul
 
         result
     }
-
-    /// Returns the DMA handle of the command queue's shared memory region.
-    pub(crate) fn dma_handle(&self) -> DmaAddress {
-        self.gsp_mem.0.dma_handle()
-    }
 }
diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
index 77054c92fcc2..c89c7b57a751 100644
--- a/drivers/gpu/nova-core/gsp/commands.rs
+++ b/drivers/gpu/nova-core/gsp/commands.rs
@@ -165,7 +165,7 @@ fn read(
 }
 
 /// Waits for GSP initialization to complete.
-pub(crate) fn wait_gsp_init_done(cmdq: &mut Cmdq) -> Result {
+pub(crate) fn wait_gsp_init_done(cmdq: &Cmdq) -> Result {
     loop {
         match cmdq.receive_msg::<GspInitDone>(Cmdq::RECEIVE_TIMEOUT) {
             Ok(_) => break Ok(()),
@@ -234,6 +234,6 @@ pub(crate) fn gpu_name(&self) -> core::result::Result<&str, GpuNameError> {
 }
 
 /// Send the [`GetGspInfo`] command and awaits for its reply.
-pub(crate) fn get_gsp_info(cmdq: &mut Cmdq, bar: &Bar0) -> Result<GetGspStaticInfoReply> {
+pub(crate) fn get_gsp_info(cmdq: &Cmdq, bar: &Bar0) -> Result<GetGspStaticInfoReply> {
     cmdq.send_command(bar, GetGspStaticInfo)
 }
diff --git a/drivers/gpu/nova-core/gsp/sequencer.rs b/drivers/gpu/nova-core/gsp/sequencer.rs
index ce2b3bb05d22..474e4c8021db 100644
--- a/drivers/gpu/nova-core/gsp/sequencer.rs
+++ b/drivers/gpu/nova-core/gsp/sequencer.rs
@@ -356,7 +356,7 @@ pub(crate) struct GspSequencerParams<'a> {
 }
 
 impl<'a> GspSequencer<'a> {
-    pub(crate) fn run(cmdq: &mut Cmdq, params: GspSequencerParams<'a>) -> Result {
+    pub(crate) fn run(cmdq: &Cmdq, params: GspSequencerParams<'a>) -> Result {
         let seq_info = loop {
             match cmdq.receive_msg::<GspSequence>(Cmdq::RECEIVE_TIMEOUT) {
                 Ok(seq_info) => break seq_info,

-- 
2.53.0