Re: [PATCH 6/6] drm/prime: document that use the page array is deprecated v2

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Oct 9, 2020 at 6:24 PM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Fri, Oct 09, 2020 at 05:03:42PM +0200, Christian König wrote:
> > We have reoccurring requests on this so better document that
> > this approach doesn't work and dma_buf_mmap() needs to be used instead.
> >
> > v2: split it into two functions
> >
> > Signed-off-by: Christian König <christian.koenig@amd.com>
>
> Patches 3-5:
>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> This one looks good, but you have it on a strange baseline. This doesn't
> contain the sg walking fixes from Marek, so reintroduces the bugs.
> Probably need to request a backmerge chain, first of -rc8 into drm-next,
> and then that into drm-misc-next.

Marek's patch is in drm-next, so just needs a backmerge into drm-misc-next.

Thomas, can you pls do that? We need 0552daac2d18f

I'll wait for the next round for patches 1&2 since Jason seems to have
found a small issue with them.
-Daniel

>
> Everything else in here lgtm.
> -Daniel
>
>
>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c     |  9 ++-
> >  drivers/gpu/drm/drm_prime.c                 | 67 +++++++++++++++------
> >  drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c |  3 +-
> >  drivers/gpu/drm/msm/msm_gem.c               |  2 +-
> >  drivers/gpu/drm/nouveau/nouveau_bo.c        |  5 +-
> >  drivers/gpu/drm/radeon/radeon_ttm.c         |  9 ++-
> >  drivers/gpu/drm/vgem/vgem_drv.c             |  3 +-
> >  drivers/gpu/drm/vkms/vkms_gem.c             |  2 +-
> >  drivers/gpu/drm/xen/xen_drm_front_gem.c     |  4 +-
> >  include/drm/drm_prime.h                     |  7 ++-
> >  10 files changed, 69 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > index ac463e706b19..6a65490de391 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > @@ -1011,8 +1011,8 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_bo_device *bdev,
> >               goto release_sg;
> >
> >       /* convert SG to linear array of pages and dma addresses */
> > -     drm_prime_sg_to_page_addr_arrays(ttm->sg, NULL, gtt->ttm.dma_address,
> > -                                      ttm->num_pages);
> > +     drm_prime_sg_to_dma_addr_array(ttm->sg, gtt->ttm.dma_address,
> > +                                    ttm->num_pages);
> >
> >       return 0;
> >
> > @@ -1345,9 +1345,8 @@ static int amdgpu_ttm_tt_populate(struct ttm_bo_device *bdev,
> >                       ttm->sg = sgt;
> >               }
> >
> > -             drm_prime_sg_to_page_addr_arrays(ttm->sg, NULL,
> > -                                              gtt->ttm.dma_address,
> > -                                              ttm->num_pages);
> > +             drm_prime_sg_to_dma_addr_array(ttm->sg, gtt->ttm.dma_address,
> > +                                            ttm->num_pages);
> >               ttm_tt_set_populated(ttm);
> >               return 0;
> >       }
> > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> > index 4910c446db83..8b750c074494 100644
> > --- a/drivers/gpu/drm/drm_prime.c
> > +++ b/drivers/gpu/drm/drm_prime.c
> > @@ -954,27 +954,25 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> >  EXPORT_SYMBOL(drm_gem_prime_import);
> >
> >  /**
> > - * drm_prime_sg_to_page_addr_arrays - convert an sg table into a page array
> > + * drm_prime_sg_to_page_array - convert an sg table into a page array
> >   * @sgt: scatter-gather table to convert
> > - * @pages: optional array of page pointers to store the page array in
> > - * @addrs: optional array to store the dma bus address of each page
> > - * @max_entries: size of both the passed-in arrays
> > + * @pages: array of page pointers to store the pages in
> > + * @max_entries: size of the passed-in array
> >   *
> > - * Exports an sg table into an array of pages and addresses. This is currently
> > - * required by the TTM driver in order to do correct fault handling.
> > + * Exports an sg table into an array of pages.
> >   *
> > - * Drivers can use this in their &drm_driver.gem_prime_import_sg_table
> > - * implementation.
> > + * This function is deprecated and strongly discouraged to be used.
> > + * The page array is only useful for page faults and those can corrupt fields
> > + * in the struct page if they are not handled by the exporting driver.
> >   */
> > -int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
> > -                                  dma_addr_t *addrs, int max_entries)
> > +int __deprecated drm_prime_sg_to_page_array(struct sg_table *sgt,
> > +                                         struct page **pages,
> > +                                         int max_entries)
> >  {
> >       unsigned count;
> >       struct scatterlist *sg;
> >       struct page *page;
> >       u32 page_len, page_index;
> > -     dma_addr_t addr;
> > -     u32 dma_len, dma_index;
> >
> >       /*
> >        * Scatterlist elements contains both pages and DMA addresses, but
> > @@ -984,14 +982,11 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
> >        * described by the sg_dma_address(sg).
> >        */
> >       page_index = 0;
> > -     dma_index = 0;
> >       for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> >               page_len = sg->length;
> >               page = sg_page(sg);
> > -             dma_len = sg_dma_len(sg);
> > -             addr = sg_dma_address(sg);
> >
> > -             while (pages && page_len > 0) {
> > +             while (page_len > 0) {
> >                       if (WARN_ON(page_index >= max_entries))
> >                               return -1;
> >                       pages[page_index] = page;
> > @@ -999,7 +994,43 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
> >                       page_len -= PAGE_SIZE;
> >                       page_index++;
> >               }
> > -             while (addrs && dma_len > 0) {
> > +     }
> > +     return 0;
> > +}
> > +EXPORT_SYMBOL(drm_prime_sg_to_page_array);
> > +
> > +/**
> > + * drm_prime_sg_to_dma_addr_array - convert an sg table into a dma addr array
> > + * @sgt: scatter-gather table to convert
> > + * @addrs: array to store the dma bus address of each page
> > + * @max_entries: size of both the passed-in arrays
> > + *
> > + * Exports an sg table into an array of addresses.
> > + *
> > + * Drivers should use this in their &drm_driver.gem_prime_import_sg_table
>
> s/should/can/
>
> There's no requirement, if your driver just handles everything as an sgt
> there's no conversion needed.
>
> > + * implementation.
> > + */
> > +int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs,
> > +                                int max_entries)
> > +{
> > +     struct scatterlist *sg;
> > +     u32 dma_len, dma_index;
> > +     dma_addr_t addr;
> > +     unsigned count;
> > +
> > +     /*
> > +      * Scatterlist elements contains both pages and DMA addresses, but
> > +      * one shoud not assume 1:1 relation between them. The sg->length is
> > +      * the size of the physical memory chunk described by the sg->page,
> > +      * while sg_dma_len(sg) is the size of the DMA (IO virtual) chunk
> > +      * described by the sg_dma_address(sg).
> > +      */
> > +     dma_index = 0;
> > +     for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> > +             dma_len = sg_dma_len(sg);
> > +             addr = sg_dma_address(sg);
> > +
> > +             while (dma_len > 0) {
> >                       if (WARN_ON(dma_index >= max_entries))
> >                               return -1;
> >                       addrs[dma_index] = addr;
> > @@ -1010,7 +1041,7 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
> >       }
> >       return 0;
> >  }
> > -EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
> > +EXPORT_SYMBOL(drm_prime_sg_to_dma_addr_array);
> >
> >  /**
> >   * drm_prime_gem_destroy - helper to clean up a PRIME-imported GEM object
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
> > index 135fbff6fecf..8c04b8e8054c 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
> > @@ -133,8 +133,7 @@ struct drm_gem_object *etnaviv_gem_prime_import_sg_table(struct drm_device *dev,
> >               goto fail;
> >       }
> >
> > -     ret = drm_prime_sg_to_page_addr_arrays(sgt, etnaviv_obj->pages,
> > -                                            NULL, npages);
> > +     ret = drm_prime_sg_to_page_array(sgt, etnaviv_obj->pages, npages);
> >       if (ret)
> >               goto fail;
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> > index a71f42870d5e..616b87641740 100644
> > --- a/drivers/gpu/drm/msm/msm_gem.c
> > +++ b/drivers/gpu/drm/msm/msm_gem.c
> > @@ -1174,7 +1174,7 @@ struct drm_gem_object *msm_gem_import(struct drm_device *dev,
> >               goto fail;
> >       }
> >
> > -     ret = drm_prime_sg_to_page_addr_arrays(sgt, msm_obj->pages, NULL, npages);
> > +     ret = drm_prime_sg_to_page_array(sgt, msm_obj->pages, npages);
> >       if (ret) {
> >               mutex_unlock(&msm_obj->lock);
> >               goto fail;
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > index e378bb491688..835edd74ef59 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > @@ -1299,9 +1299,8 @@ nouveau_ttm_tt_populate(struct ttm_bo_device *bdev,
> >               return 0;
> >
> >       if (slave && ttm->sg) {
> > -             drm_prime_sg_to_page_addr_arrays(ttm->sg, NULL,
> > -                                              ttm_dma->dma_address,
> > -                                              ttm->num_pages);
> > +             drm_prime_sg_to_dma_addr_array(ttm->sg, ttm_dma->dma_address,
> > +                                            ttm->num_pages);
> >               ttm_tt_set_populated(ttm);
> >               return 0;
> >       }
> > diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
> > index 4b92cdbcd29b..7997e4564576 100644
> > --- a/drivers/gpu/drm/radeon/radeon_ttm.c
> > +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> > @@ -474,8 +474,8 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_bo_device *bdev, struct ttm_tt *
> >       if (r)
> >               goto release_sg;
> >
> > -     drm_prime_sg_to_page_addr_arrays(ttm->sg, NULL, gtt->ttm.dma_address,
> > -                                      ttm->num_pages);
> > +     drm_prime_sg_to_dma_addr_array(ttm->sg, gtt->ttm.dma_address,
> > +                                    ttm->num_pages);
> >
> >       return 0;
> >
> > @@ -642,9 +642,8 @@ static int radeon_ttm_tt_populate(struct ttm_bo_device *bdev,
> >       }
> >
> >       if (slave && ttm->sg) {
> > -             drm_prime_sg_to_page_addr_arrays(ttm->sg, NULL,
> > -                                              gtt->ttm.dma_address,
> > -                                              ttm->num_pages);
> > +             drm_prime_sg_to_dma_addr_array(ttm->sg, gtt->ttm.dma_address,
> > +                                            ttm->num_pages);
> >               ttm_tt_set_populated(ttm);
> >               return 0;
> >       }
> > diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> > index ea0eecae5153..e505e5a291b3 100644
> > --- a/drivers/gpu/drm/vgem/vgem_drv.c
> > +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> > @@ -356,8 +356,7 @@ static struct drm_gem_object *vgem_prime_import_sg_table(struct drm_device *dev,
> >       }
> >
> >       obj->pages_pin_count++; /* perma-pinned */
> > -     drm_prime_sg_to_page_addr_arrays(obj->table, obj->pages, NULL,
> > -                                     npages);
> > +     drm_prime_sg_to_page_array(obj->table, obj->pages, npages);
> >       return &obj->base;
> >  }
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_gem.c
> > index 19a0e260a4df..a2ff21f47101 100644
> > --- a/drivers/gpu/drm/vkms/vkms_gem.c
> > +++ b/drivers/gpu/drm/vkms/vkms_gem.c
> > @@ -256,6 +256,6 @@ vkms_prime_import_sg_table(struct drm_device *dev,
> >               return ERR_PTR(-ENOMEM);
> >       }
> >
> > -     drm_prime_sg_to_page_addr_arrays(sg, obj->pages, NULL, npages);
> > +     drm_prime_sg_to_page_array(sg, obj->pages, npages);
> >       return &obj->gem;
> >  }
> > diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
> > index f3830a0d1808..f4150ddfc5e2 100644
> > --- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
> > +++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
> > @@ -220,8 +220,8 @@ xen_drm_front_gem_import_sg_table(struct drm_device *dev,
> >
> >       xen_obj->sgt_imported = sgt;
> >
> > -     ret = drm_prime_sg_to_page_addr_arrays(sgt, xen_obj->pages,
> > -                                            NULL, xen_obj->num_pages);
> > +     ret = drm_prime_sg_to_page_array(sgt, xen_obj->pages,
> > +                                      xen_obj->num_pages);
> >       if (ret < 0)
> >               return ERR_PTR(ret);
> >
> > diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
> > index 093f760cc131..4bda9ab3a3bb 100644
> > --- a/include/drm/drm_prime.h
> > +++ b/include/drm/drm_prime.h
> > @@ -103,8 +103,9 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> >
> >  void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg);
> >
> > -int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
> > -                                  dma_addr_t *addrs, int max_pages);
> > -
> > +int drm_prime_sg_to_page_array(struct sg_table *sgt, struct page **pages,
> > +                            int max_pages);
> > +int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs,
> > +                                int max_pages);
> >
> >  #endif /* __DRM_PRIME_H__ */
> > --
> > 2.17.1
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch