Please squash that together with patch #3 in this series.
On 12.09.25 13:11, Srinivasan Shanmugam wrote:
> Add helpers to map/unmap a hardware MMIO register window (PCI BAR) as a
> 1-entry sg_table using dma_map_resource()/dma_unmap_resource(). This
> will be used by MMIO_REMAP.
>
> Cc: Christian König <christian.koe...@amd.com>
> Cc: Alex Deucher <alexander.deuc...@amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 51 +++++++++++++++++++++
> 1 file changed, 51 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index ff98c87b2e0b..33fa17a927ce 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -37,11 +37,15 @@
> #include "amdgpu_dma_buf.h"
> #include "amdgpu_xgmi.h"
> #include "amdgpu_vm.h"
> +#include "amdgpu_object.h"
> #include <drm/amdgpu_drm.h>
> #include <drm/ttm/ttm_tt.h>
> #include <linux/dma-buf.h>
> #include <linux/dma-fence-array.h>
> #include <linux/pci-p2pdma.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/scatterlist.h>
> +#include <linux/slab.h>
>
> static const struct dma_buf_attach_ops amdgpu_dma_buf_attach_ops;
>
> @@ -146,6 +150,53 @@ static void amdgpu_dma_buf_unpin(struct
> dma_buf_attachment *attach)
> amdgpu_bo_unpin(bo);
> }
>
> +/* Map a BAR-backed I/O span as a 1-entry sg_table via dma_map_resource(). */
> +static __maybe_unused struct sg_table *
> +amdgpu_dmabuf_map_iomem(struct device *dev, resource_size_t phys,
> + size_t size, enum dma_data_direction dir)
> +{
> + struct sg_table *sgt;
> + unsigned long attrs = DMA_ATTR_SKIP_CPU_SYNC; /* no P2PDMA attr */
> + dma_addr_t dma;
> +
> + sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
> + if (!sgt)
> + return ERR_PTR(-ENOMEM);
> +
> + if (sg_alloc_table(sgt, 1, GFP_KERNEL)) {
> + kfree(sgt);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + /* No struct page backing for I/O regions. */
> + sg_set_page(sgt->sgl, NULL, size, 0);
> +
> + dma = dma_map_resource(dev, phys, size, dir, attrs);
> + if (dma_mapping_error(dev, dma)) {
> + sg_free_table(sgt);
> + kfree(sgt);
> + return ERR_PTR(-EIO);
> + }
> +
> + sg_dma_address(sgt->sgl) = dma;
> + sg_dma_len(sgt->sgl) = size;
> + return sgt;
> +}
> +
> +static __maybe_unused void
> +amdgpu_dmabuf_unmap_iomem(struct device *dev, struct sg_table *sgt,
> + enum dma_data_direction dir)
> +{
> + /* attrs must match map side; we only used SKIP_CPU_SYNC above */
> + dma_unmap_resource(dev,
> + sg_dma_address(sgt->sgl),
> + sg_dma_len(sgt->sgl),
> + dir,
> + 0);
> + sg_free_table(sgt);
> + kfree(sgt);
> +}
> +
> /**
> * amdgpu_dma_buf_map - &dma_buf_ops.map_dma_buf implementation
> * @attach: DMA-buf attachment
