Re: [PATCH 3/4] drm/nouveau: stop using is_swiotlb_active

[Lyude Paul <lyude@xxxxxxxxxx>]

Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>

Thanks for getting to this!

On Thu, 2023-05-18 at 15:42 +0200, Christoph Hellwig wrote:
> Drivers have no business looking into dma-mapping internals and check
> what backend is used.  Unfortunstely the DRM core is still broken and
> tries to do plain page allocations instead of using DMA API allocators
> by default and uses various bandaids on when to use dma_alloc_coherent.
> 
> Switch nouveau to use the same (broken) scheme as amdgpu and radeon
> to remove the last driver user of is_swiotlb_active.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>  drivers/gpu/drm/nouveau/nouveau_ttm.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_ttm.c 
> b/drivers/gpu/drm/nouveau/nouveau_ttm.c
> index 1469a88910e45d..486f39f31a38df 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_ttm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_ttm.c
> @@ -24,9 +24,9 @@
>   */
>  
>  #include <linux/limits.h>
> -#include <linux/swiotlb.h>
>  
>  #include <drm/ttm/ttm_range_manager.h>
> +#include <drm/drm_cache.h>
>  
>  #include "nouveau_drv.h"
>  #include "nouveau_gem.h"
> @@ -265,7 +265,6 @@ nouveau_ttm_init(struct nouveau_drm *drm)
>       struct nvkm_pci *pci = device->pci;
>       struct nvif_mmu *mmu = &drm->client.mmu;
>       struct drm_device *dev = drm->dev;
> -     bool need_swiotlb = false;
>       int typei, ret;
>  
>       ret = nouveau_ttm_init_host(drm, 0);
> @@ -300,13 +299,10 @@ nouveau_ttm_init(struct nouveau_drm *drm)
>               drm->agp.cma = pci->agp.cma;
>       }
>  
> -#if IS_ENABLED(CONFIG_SWIOTLB) && IS_ENABLED(CONFIG_X86)
> -     need_swiotlb = is_swiotlb_active(dev->dev);
> -#endif
> -
>       ret = ttm_device_init(&drm->ttm.bdev, &nouveau_bo_driver, drm->dev->dev,
>                                 dev->anon_inode->i_mapping,
> -                               dev->vma_offset_manager, need_swiotlb,
> +                               dev->vma_offset_manager,
> +                               drm_need_swiotlb(drm->client.mmu.dmabits),
>                                 drm->client.mmu.dmabits <= 32);
>       if (ret) {
>               NV_ERROR(drm, "error initialising bo driver, %d\n", ret);

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat