Re: [PATCH v3 3/5] gpu: nova-core: gsp: add reply/no-reply info to `CommandToGsp`

["Alexandre Courbot" <acourbot@nvidia.com>]

On Thu Mar 5, 2026 at 10:34 AM JST, Eliot Courtney wrote:
> On Wed Mar 4, 2026 at 8:56 PM JST, Alexandre Courbot wrote:
>>> +    /// 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),
>>> +            }
>>> +        }
>>
>> There is an opportunity for factorize some more code here.
>>
>> Notice how the other callers of `receive_msg` (`wait_gsp_init_done` and
>> `GspSequencer::run`) both use the same kind of loop, down to the same
>> error handling. We could move that loop logic here and do it in a single
>> place.
>>
>> In the future, we will probably want to add handlers for
>> unexpected messages from the GSP and it will be easier if we receive all
>> messages from a single place.
>>
>> This can be a separate patch from this one, but I think it makes sense
>> to have that in this series.
>>
>> I expect the last patch to change a bit as a consequence of that - maybe
>> we will need a `receive_msg_loop` or something in `CmdqInner`.
>
> I agree we should migrate all callers and make Cmdq responsible for
> draining / handling spontaneous messages from the GSP, but I was
> planning on doing it in a separate patch series until now. I can put it
> into this one though if you want though no worries.

If it ends up being convulated, let's do that afterwards but since it
looks like a quick and easy win I thought it would make sense to have it
here. Your call though.