linux-kernel - Re: [PATCH v2 01/10] gpu: nova-core: Set correct DMA mask

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Message-ID: <aNFqTYkkY4qgCyWP@tardis.local>
Date: Mon, 22 Sep 2025 08:25:01 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Alistair Popple <apopple@...dia.com>
Cc: rust-for-linux@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	dakr@...nel.org, acourbot@...dia.com,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <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>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Timur Tabi <ttabi@...dia.com>, linux-kernel@...r.kernel.org,
	nouveau@...ts.freedesktop.org
Subject: Re: [PATCH v2 01/10] gpu: nova-core: Set correct DMA mask

On Mon, Sep 22, 2025 at 09:30:17PM +1000, Alistair Popple wrote:
> Set the correct DMA mask. Without this DMA will fail on some setups.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> 
> ---
> 
> Changes for v2:
> 
>  - Update DMA mask to correct value for Ampere/Turing (47 bits)
> ---
>  drivers/gpu/nova-core/driver.rs | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> index 1380b47617f7..ccc97340206e 100644
> --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -1,6 +1,9 @@
>  // SPDX-License-Identifier: GPL-2.0
>  
> -use kernel::{auxiliary, bindings, c_str, device::Core, pci, prelude::*, sizes::SZ_16M, sync::Arc};
> +use kernel::{
> +    auxiliary, bindings, c_str, device::Core, dma::Device, dma::DmaMask, pci, prelude::*,
> +    sizes::SZ_16M, sync::Arc,
> +};
>  
>  use crate::gpu::Gpu;
>  
> @@ -34,6 +37,9 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self
>          pdev.enable_device_mem()?;
>          pdev.set_master();
>  
> +        // SAFETY: No DMA allocations have been made yet
> +        unsafe { pdev.dma_set_mask_and_coherent(DmaMask::new::<47>())? };

Any chance you give it this a const name? Otherwise 6 months later it
becomes a magic number ;-)

Otherwise than this,

Reviewed-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> +
>          let devres_bar = Arc::pin_init(
>              pdev.iomap_region_sized::<BAR0_SIZE>(0, c_str!("nova-core/bar0")),
>              GFP_KERNEL,
> -- 
> 2.50.1
>