Messages in this thread |  | | Subject | Re: [PATCH v4 1/3] drm: Add support for GEM buffers backed by non-coherent memory | From | Thomas Zimmermann <> | Date | Sat, 15 May 2021 20:49:08 +0200 |
| |
Am 15.05.21 um 16:53 schrieb Paul Cercueil: > Having GEM buffers backed by non-coherent memory is interesting in the > particular case where it is faster to render to a non-coherent buffer > then sync the data cache, than to render to a write-combine buffer, and > (by extension) much faster than using a shadow buffer. This is true for > instance on some Ingenic SoCs, where even simple blits (e.g. memcpy) > are about three times faster using this method. > > Add a 'map_noncoherent' flag to the drm_gem_cma_object structure, which > can be set by the drivers when they create the dumb buffer. > > Since this really only applies to software rendering, disable this flag > as soon as the CMA objects are exported via PRIME. > > v3: New patch. Now uses a simple 'map_noncoherent' flag to control how > the objects are mapped, and use the new dma_mmap_pages function. > > v4: Make sure map_noncoherent is always disabled when creating GEM > objects meant to be used with dma-buf. > > Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
> --- > drivers/gpu/drm/drm_gem_cma_helper.c | 38 +++++++++++++++++++++------- > include/drm/drm_gem_cma_helper.h | 3 +++ > 2 files changed, 32 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c > index 7942cf05cd93..235c7a63da2b 100644 > --- a/drivers/gpu/drm/drm_gem_cma_helper.c > +++ b/drivers/gpu/drm/drm_gem_cma_helper.c > @@ -46,6 +46,7 @@ static const struct drm_gem_object_funcs drm_gem_cma_default_funcs = { > * __drm_gem_cma_create - Create a GEM CMA object without allocating memory > * @drm: DRM device > * @size: size of the object to allocate > + * @private: true if used for internal purposes > * > * This function creates and initializes a GEM CMA object of the given size, > * but doesn't allocate any memory to back the object. > @@ -55,11 +56,11 @@ static const struct drm_gem_object_funcs drm_gem_cma_default_funcs = { > * error code on failure. > */ > static struct drm_gem_cma_object * > -__drm_gem_cma_create(struct drm_device *drm, size_t size) > +__drm_gem_cma_create(struct drm_device *drm, size_t size, bool private) > { > struct drm_gem_cma_object *cma_obj; > struct drm_gem_object *gem_obj; > - int ret; > + int ret = 0; > > if (drm->driver->gem_create_object) > gem_obj = drm->driver->gem_create_object(drm, size); > @@ -73,7 +74,14 @@ __drm_gem_cma_create(struct drm_device *drm, size_t size) > > cma_obj = container_of(gem_obj, struct drm_gem_cma_object, base); > > - ret = drm_gem_object_init(drm, gem_obj, size); > + if (private) { > + drm_gem_private_object_init(drm, gem_obj, size); > + > + /* Always use writecombine for dma-buf mappings */ > + cma_obj->map_noncoherent = false; > + } else { > + ret = drm_gem_object_init(drm, gem_obj, size); > + } > if (ret) > goto error; > > @@ -111,12 +119,19 @@ struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm, > > size = round_up(size, PAGE_SIZE); > > - cma_obj = __drm_gem_cma_create(drm, size); > + cma_obj = __drm_gem_cma_create(drm, size, false); > if (IS_ERR(cma_obj)) > return cma_obj; > > - cma_obj->vaddr = dma_alloc_wc(drm->dev, size, &cma_obj->paddr, > - GFP_KERNEL | __GFP_NOWARN); > + if (cma_obj->map_noncoherent) { > + cma_obj->vaddr = dma_alloc_noncoherent(drm->dev, size, > + &cma_obj->paddr, > + DMA_TO_DEVICE, > + GFP_KERNEL | __GFP_NOWARN); > + } else { > + cma_obj->vaddr = dma_alloc_wc(drm->dev, size, &cma_obj->paddr, > + GFP_KERNEL | __GFP_NOWARN); > + } > if (!cma_obj->vaddr) { > drm_dbg(drm, "failed to allocate buffer with size %zu\n", > size); > @@ -432,7 +447,7 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev, > return ERR_PTR(-EINVAL); > > /* Create a CMA GEM buffer. */ > - cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size); > + cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size, true); > if (IS_ERR(cma_obj)) > return ERR_CAST(cma_obj); > > @@ -499,8 +514,13 @@ int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma) > > cma_obj = to_drm_gem_cma_obj(obj); > > - ret = dma_mmap_wc(cma_obj->base.dev->dev, vma, cma_obj->vaddr, > - cma_obj->paddr, vma->vm_end - vma->vm_start); > + 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)); > if (ret) > drm_gem_vm_close(vma); > > diff --git a/include/drm/drm_gem_cma_helper.h b/include/drm/drm_gem_cma_helper.h > index 0a9711caa3e8..cd13508acbc1 100644 > --- a/include/drm/drm_gem_cma_helper.h > +++ b/include/drm/drm_gem_cma_helper.h > @@ -16,6 +16,7 @@ struct drm_mode_create_dumb; > * more than one entry but they are guaranteed to have contiguous > * DMA addresses. > * @vaddr: kernel virtual address of the backing memory > + * @map_noncoherent: if true, the GEM object is backed by non-coherent memory > */ > struct drm_gem_cma_object { > struct drm_gem_object base; > @@ -24,6 +25,8 @@ struct drm_gem_cma_object { > > /* For objects with DMA memory allocated by GEM CMA */ > void *vaddr; > + > + bool map_noncoherent; > }; > > #define to_drm_gem_cma_obj(gem_obj) \ >
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
[unhandled content-type:application/pgp-signature]
|  |