On Mon, Nov 02, 2020 at 10:06:49PM +0000, Paul Cercueil wrote: > This function can be used by drivers that need to mmap dumb buffers > created with non-coherent backing memory. > > Signed-off-by: Paul Cercueil <p...@crapouillou.net> > --- > drivers/gpu/drm/drm_gem_cma_helper.c | 39 ++++++++++++++++++++++++++++ > include/drm/drm_gem_cma_helper.h | 2 ++ > 2 files changed, 41 insertions(+) > > diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c > b/drivers/gpu/drm/drm_gem_cma_helper.c > index 3bdd67795e20..4ed63f4896bd 100644 > --- a/drivers/gpu/drm/drm_gem_cma_helper.c > +++ b/drivers/gpu/drm/drm_gem_cma_helper.c > @@ -387,6 +387,45 @@ int drm_gem_cma_mmap(struct file *filp, struct > vm_area_struct *vma) > } > EXPORT_SYMBOL_GPL(drm_gem_cma_mmap); > > +/** > + * drm_gem_cma_mmap_noncoherent - memory-map a CMA GEM object with > + * non-coherent cache attribute > + * @filp: file object > + * @vma: VMA for the area to be mapped > + * > + * Just like drm_gem_cma_mmap, but for a GEM object backed by non-coherent > + * memory. > + * > + * Returns: > + * 0 on success or a negative error code on failure. > + */ > +int drm_gem_cma_mmap_noncoherent(struct file *filp, struct vm_area_struct > *vma) > +{ > + struct drm_gem_cma_object *cma_obj; > + int ret; > + > + ret = drm_gem_mmap(filp, vma); > + if (ret) > + return ret; > + > + cma_obj = to_drm_gem_cma_obj(vma->vm_private_data); > + > + /* > + * 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; > + vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); > + > + return remap_pfn_range(vma, vma->vm_start, > + cma_obj->paddr >> PAGE_SHIFT, > + vma->vm_end - vma->vm_start, > + vma->vm_page_prot);
Per patch 1 cma_obj->paddr is the dma address, while remap_pfn_range expects a physical address. This does not work.