Hi Dave,
Could you please take this patch in your tree ?
On Sunday 02 March 2014 20:09:48 Laurent Pinchart wrote:
> The GEM CMA helpers uses a custom mmap implementation based on
> remap_pfn_range(). While this works when the buffer DMA and physical
> addresses are identical, it fails to take IOMMU into account and tries
> to mmap the buffer to userspace using the DMA virtual address instead of
> the physical address. This results in mapping random physical pages when
> the device is behind an IOMMU.
>
> Use the DMA mapping dma_mmap_writecombine() function instead.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> ---
> drivers/gpu/drm/drm_gem_cma_helper.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> This patches fixes a problem noticed when enabling IOMMU usage with the
> Renesas R-Car DU driver. I've tested it both with the IOMMU enabled and
> disabled.
>
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c
> b/drivers/gpu/drm/drm_gem_cma_helper.c index 6b51bf9..1d4fd34 100644
> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -253,8 +253,17 @@ static int drm_gem_cma_mmap_obj(struct
> drm_gem_cma_object *cma_obj, {
> int ret;
>
> - ret = remap_pfn_range(vma, vma->vm_start, cma_obj->paddr >> PAGE_SHIFT,
> - vma->vm_end - vma->vm_start, vma->vm_page_prot);
> + /*
> + * Clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the
> + * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map
> + * the whole buffer.
> + */
> + vma->vm_flags &= ~VM_PFNMAP;
> + vma->vm_pgoff = 0;
> +
> + ret = dma_mmap_writecombine(cma_obj->base.dev->dev, vma,
> + cma_obj->vaddr, cma_obj->paddr,
> + vma->vm_end - vma->vm_start);
> if (ret)
> drm_gem_vm_close(vma);
--
Regards,
Laurent Pinchart
