linux-kernel - Re: [PATCH v2 06/12] nova-core: Add bindings required by GSP sequencer

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Message-Id: <DE6BESY0QHEZ.2DX2FQ6HF8BY6@nvidia.com>
Date: Wed, 12 Nov 2025 10:12:00 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Joel Fernandes" <joelagnelf@...dia.com>, "Alexandre Courbot"
 <acourbot@...dia.com>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
 <dakr@...nel.org>
Cc: "Alistair Popple" <apopple@...dia.com>, "Miguel Ojeda"
 <ojeda@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>, "Boqun Feng"
 <boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
 <bjorn3_gh@...tonmail.com>, "Benno Lossin" <lossin@...nel.org>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "David Airlie" <airlied@...il.com>,
 "Simona Vetter" <simona@...ll.ch>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "John Hubbard"
 <jhubbard@...dia.com>, "Timur Tabi" <ttabi@...dia.com>,
 <joel@...lfernandes.org>, <nouveau@...ts.freedesktop.org>, "Nouveau"
 <nouveau-bounces@...ts.freedesktop.org>
Subject: Re: [PATCH v2 06/12] nova-core: Add bindings required by GSP
 sequencer

On Wed Nov 12, 2025 at 7:06 AM JST, Joel Fernandes wrote:
>
>
> On 11/10/2025 8:39 AM, Alexandre Courbot wrote:
>>> +    // GSP sequencer delay payload structure.
>>> +    GSP_SEQ_BUF_PAYLOAD_DELAY_US,
>>> +
>>> +    // GSP sequencer register payload structures.
>>> +    GSP_SEQ_BUF_PAYLOAD_REG_MODIFY,
>>> +    GSP_SEQ_BUF_PAYLOAD_REG_POLL,
>>> +    GSP_SEQ_BUF_PAYLOAD_REG_STORE,
>>> +    GSP_SEQ_BUF_PAYLOAD_REG_WRITE, //
>>> These ones are a bit trickier to abstract. Since they ever only use
>> `bar` from the sequencer, I guess we can have their semantics in the
>> `fw` module, exposed through a method that receives the `bar`? That way
>> the sequencer won't have to access their members which are private to
>> it.
>
> The sequencer does need access to the private fields, because the logic of what
> to write to the bar should be in the sequencer, and that logic depends on the
> fields.
>
> Example:
>
> impl GspSeqCmdRunner for fw::GSP_SEQ_BUF_PAYLOAD_REG_MODIFY {
>     fn run(&self, sequencer: &GspSequencer<'_>) -> Result {
>         let addr = self.addr as usize;
>         if let Ok(temp) = sequencer.bar.try_read32(addr) {
>             let _ = sequencer
>                 .bar
>                 .try_write32((temp & !self.mask) | self.val, addr);
>         }
>         Ok(())
>     }
> }
>
> Here, the sequencer needs access to `.addr`, `.mask` and `.val` to craft the
> address and the value to write.
>
> I could expose access to those fields as functions, but I think we should not
> move sequencer logic to fw.rs, that should live in the sequencer.

Yeah although I floated the idea I have to admit I am not a big fan of
that either. So I guess we could have accessor functions for the fields,
so the `GspSeqCmdRunner` implementation stays in the sequencer?

It will at least provide the level of abstraction we require against the
firmware types' internal structure.