Re: [PATCH v2] gpu: nova-core: falcon: pad firmware DMA object size to required block alignment

["Danilo Krummrich" <dakr@kernel.org>]

On Sun Apr 5, 2026 at 4:22 AM CEST, Alexandre Courbot wrote:
> Commit a88831502c8f ("gpu: nova-core: falcon: use dma::Coherent")
> dropped the nova-local `DmaObject` device memory type for the
> kernel-global `Coherent` one.
>
> This switch had a side-effect: `DmaObject` always aligned the requested
> size to `PAGE_SIZE`, and also reported that adjusted size when queried.
> `Coherent`, on the other hand, does page-align allocation sizes but only
> allows CPU access on the exact size provided by the caller.
>
> This change runs into a limitation of falcon DMA copies, namely that DMA
> accesses are done on blocks of exactly 256 bytes. If the provided data
> does not have a length that is a multiple of 256, `dma_wr` returns
> an error.
>
> It was expected that all firmwares would present the proper adjusted
> size, but this is not the case at least on my GA107:
>
>     NovaCore 0000:08:00.0: DMA transfer goes beyond range of DMA object
>     NovaCore 0000:08:00.0: Failed to load FWSEC firmware: EINVAL
>     NovaCore 0000:08:00.0: probe with driver NovaCore failed with error -22
>
> Fix this by padding the `Coherent`'s size to `MEM_BLOCK_ALIGNMENT` (i.e.
> 256) when allocating it and filling it with zeroes, before copying the
> firmware on top of it.
>
> Fixes: a88831502c8f ("gpu: nova-core: falcon: use dma::Coherent")
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Reviewed-by: Gary Guo <gary@garyguo.net>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

Applied to drm-rust-next, thanks!