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Date: Tue, 30 Sep 2025 15:29:41 +0200
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Subject: Re: [PATCH v3 01/13] gpu: nova-core: Set correct DMA mask
To: Alistair Popple <apopple@nvidia.com>
Cc: rust-for-linux@vger.kernel.org, dri-devel@lists.freedesktop.org,
 acourbot@nvidia.com, Miguel Ojeda <ojeda@kernel.org>,
 Alex Gaynor <alex.gaynor@gmail.com>, Boqun Feng <boqun.feng@gmail.com>,
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 <bjorn3_gh@protonmail.com>, Benno Lossin <lossin@kernel.org>,
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 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
 John Hubbard <jhubbard@nvidia.com>, Joel Fernandes <joelagnelf@nvidia.com>,
 Timur Tabi <ttabi@nvidia.com>, linux-kernel@vger.kernel.org,
 nouveau@lists.freedesktop.org
References: <20250930131648.411720-1-apopple@nvidia.com>
 <20250930131648.411720-2-apopple@nvidia.com>
From: Danilo Krummrich <dakr@kernel.org>
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In-Reply-To: <20250930131648.411720-2-apopple@nvidia.com>
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On 9/30/25 3:16 PM, Alistair Popple wrote:
> +        // SAFETY: No DMA allocations have been made yet
> +        unsafe { pdev.dma_set_mask_and_coherent(DmaMask::new::<47>())? };

I think you forgot to derive the value from the relevant sources, i.e. physical
bus, DMA controller and MMU capabilities.

I assume not all GPU architectures / generations have the exact same capabilities?