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.koe...@amd.com>
---
 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
+ * 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

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