Messages in this thread |  | | Date | Tue, 03 Nov 2020 19:13:27 +0000 | From | Paul Cercueil <> | Subject | Re: [PATCH 3/5] drm: Add and export function
drm_gem_cma_mmap_noncoherent |
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Hi Christoph,
Le mar. 3 nov. 2020 à 18:50, Christoph Hellwig <hch@infradead.org> a écrit : > 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 <paul@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.
Ok, what would be the correct way to mmap_noncoherent?
-Paul
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