Re: [PATCH v2 3/5] drm: Add and export function drm_gem_cma_mmap_noncoherent

[Paul Cercueil]

Hi Christoph,

Le jeu. 11 mars 2021 à 12:26, Christoph Hellwig <hch@xxxxxxxxxxxxx> a 
écrit :
> >  +int drm_gem_cma_mmap_noncoherent(struct drm_gem_object *obj,
> >  +				 struct vm_area_struct *vma)
> >  +{
> >  +	struct drm_gem_cma_object *cma_obj;
> >  +	unsigned long pfn;
> >  +	int ret;
> >  +
> >  +	/*
> >  +	 * 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_pgoff -= drm_vma_node_start(&obj->vma_node);
> >  +	vma->vm_flags &= ~VM_PFNMAP;
> >  +	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
> >  +
> >  +	cma_obj = to_drm_gem_cma_obj(obj);
> >  +
> >  +	pfn = PHYS_PFN(dma_to_phys(cma_obj->base.dev->dev, 
> > cma_obj->paddr));
> >  +
> >  +	ret = remap_pfn_range(vma, vma->vm_start, pfn,
> >  +			      vma->vm_end - vma->vm_start,
> >  +			      vma->vm_page_prot);
>
> dma_to_phys must not be used by drivers.
>
> I have a proper helper for this waiting for users:
>
> http://git.infradead.org/users/hch/misc.git/commitdiff/96a546e7229ec53aadbdb7936d1e5e6cb5958952
>
> If you can confirm the helpers works for you I can try to still sneak
> it to Linus for 5.12 to ease the merge pain.

I can try. How do I get a page pointer from a dma_addr_t?

-Paul