merged.

Bruce

In message: [linux-yocto][linux-yocto v6.12/standard/bcm-2xxx-rpi & 
v6.12/standard/preempt-rt/bcm-2xxx-rpi][PATCH] Drivers: IOMMU: set the IOMMU sg 
limitation segment
on 13/11/2025 Xiaolei Wang wrote:

> the kernel occasionally reports a segment size mismatch.
> This is because 'max_seg_size' is not set. The kernel
> defaults to 64K. Based on IOMMU addressing capabilities,
> setting 'max_seg_size' to the maximum will prevent
> 'debug_dma_map_sg()' from complaining about the over-mapping
> of the IOMMU segment length.
> 
> DMA-API: bcm2712-iommu 1000005100.iommu: mapping sg segment longer than 
> device claims to support [len=2105344] [max=65536]
>  WARNING: CPU: 0 PID: 59 at /kernel/dma/debug.c:1178 
> check_sg_segment+0x190/0x200
>  Modules linked in:
>  CPU: 0 UID: 0 PID: 59 Comm: kworker/u16:1 Tainted: G        W          
> 6.12.55-rt6-yocto-preempt-rt #1
>  Call trace:
>   check_sg_segment+0x190/0x200
>   debug_dma_map_sg+0x13c/0x1b0
>   dma_alloc_noncontiguous+0x98/0x118
>   bcm2712_iommu_probe+0x15c/0x320
>   platform_probe+0x70/0xe8
> 
> Signed-off-by: Xiaolei Wang <[email protected]>
> ---
>  drivers/iommu/bcm2712-iommu.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/bcm2712-iommu.c b/drivers/iommu/bcm2712-iommu.c
> index 4e6aa0352f5a..a9ae51d593ca 100644
> --- a/drivers/iommu/bcm2712-iommu.c
> +++ b/drivers/iommu/bcm2712-iommu.c
> @@ -607,6 +607,7 @@ static int bcm2712_iommu_probe(struct platform_device 
> *pdev)
>        */
>       ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(36));
>       WARN_ON(ret);
> +     dma_set_max_seg_size(&pdev->dev, UINT_MAX);
>       mmu->sgt = dma_alloc_noncontiguous(&pdev->dev, TABLES_ALLOC_SIZE,
>                                          DMA_TO_DEVICE, GFP_KERNEL,
>                                          DMA_ATTR_ALLOC_SINGLE_PAGES);
> -- 
> 2.43.0
> 
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