Unverified Commit 162ba3bd authored May 28, 2021 by Paul Cercueil

drm: Fix for GEM buffers with write-combine memory

The previous commit wrongly assumed that dma_mmap_wc() could be replaced
by pgprot_writecombine() + dma_mmap_pages(). It did work on my setup,
but did not work everywhere.

Use dma_mmap_wc() when the buffer has the write-combine cache attribute,
and dma_mmap_pages() when it has the non-coherent cache attribute.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reported-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Fixes: cf8ccbc7 ("drm: Add support for GEM buffers backed by non-coherent memory")
Link: https://patchwork.freedesktop.org/patch/msgid/20210527230334.151947-1-paul@crapouillou.net

parent 71b970c8

drivers/gpu/drm/drm_gem_cma_helper.c

+9 −6

Original line number	Diff line number	Diff line
		@@ -514,13 +514,16 @@ int drm_gem_cma_mmap(struct drm_gem_object obj, struct vm_area_struct vma)

		cma_obj = to_drm_gem_cma_obj(obj);

		if (cma_obj->map_noncoherent) {
		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
		if (!cma_obj->map_noncoherent)
		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

		ret = dma_mmap_pages(cma_obj->base.dev->dev,
		vma, vma->vm_end - vma->vm_start,
		virt_to_page(cma_obj->vaddr));
		} else {
		ret = dma_mmap_wc(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);