Commit 0e0ffbcd authored by Alexandre Courbot's avatar Alexandre Courbot Committed by Danilo Krummrich
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gpu: nova-core: falcon: pad firmware DMA object size to required block alignment 



Commit a8883150 ("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: a8883150 ("gpu: nova-core: falcon: use dma::Coherent")
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Signed-off-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260405-falcon-dma-roundup-v2-1-4af5b2ff9c16@nvidia.com


Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
parent 8e6c3478

drivers/gpu/nova-core/falcon.rs

+19 −2
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
    },

    dma::{

        Coherent,

        CoherentBox,

        DmaAddress,

        DmaMask, //

    },
@@ -613,8 +614,24 @@ fn dma_load<F: FalconFirmware<Target = E> + FalconDmaLoadable>( 
        bar: &Bar0,

        fw: &F,

    ) -> Result {

        // Create DMA object with firmware content as the source of the DMA engine.

        let dma_obj = Coherent::from_slice(dev, fw.as_slice(), GFP_KERNEL)?;

        // DMA object with firmware content as the source of the DMA engine.

        let dma_obj = {

            let fw_slice = fw.as_slice();



            // DMA copies are done in chunks of `MEM_BLOCK_ALIGNMENT`, so pad the length

            // accordingly and fill with `0`.

            let mut dma_obj = CoherentBox::zeroed_slice(

                dev,

                fw_slice.len().next_multiple_of(MEM_BLOCK_ALIGNMENT),

                GFP_KERNEL,

            )?;



            // PANIC: `dma_obj` has been created with a length equal to or larger than

            // `fw_slice.len()`, so the range `..fw_slice.len()` is valid.

            dma_obj[..fw_slice.len()].copy_from_slice(fw_slice);



            dma_obj.into()

        };



        self.dma_reset(bar);

        bar.update(regs::NV_PFALCON_FBIF_TRANSCFG::of::<E>().at(0), |v| {