drm: exynos: fix for mapping of dma buffers

This patch fixes the problem of mapping contigous and non contigous dma buffers.

Currently page struct is calculated from the buf->dma_addr which is not the
physical address. It is replaced by buf->pages which points to the page struct
of the first page of contigous memory chunk. This gives the correct page frame
number for mapping.

Non-contigous dma buffers are described using SG table and SG lists. Each
valid SG List is pointing to a single page or group of pages which are
physically contigous. Current implementation just maps the first page of each
SG List and leave the other pages unmapped, leading to a crash. Given solution
finds the page struct for the faulting page through parsing SG table and map it.

Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

1 files changed, 25 insertions, 3 deletions

diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
index b130e6d1a529..5fdfb8f51a41 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
@@ -95,15 +95,37 @@ static int exynos_drm_gem_map_buf(struct drm_gem_object *obj,
 {
         struct exynos_drm_gem_obj *exynos_gem_obj = to_exynos_gem_obj(obj);
         struct exynos_drm_gem_buf *buf = exynos_gem_obj->buffer;
+        struct scatterlist *sgl;
         unsigned long pfn;
+        int i;
 
         if (exynos_gem_obj->flags & EXYNOS_BO_NONCONTIG) {
+                if (!buf->sgt)
+                        return -EINTR;
+
+                sgl = buf->sgt->sgl;
+                for_each_sg(buf->sgt->sgl, sgl, buf->sgt->nents, i) {
+                        if (!sgl) {
+                                DRM_ERROR("invalid SG table\n");
+                                return -EINTR;
+                        }
+                        if (page_offset < (sgl->length >> PAGE_SHIFT))
+                                break;
+                        page_offset -=  (sgl->length >> PAGE_SHIFT);
+                }
+
+                if (i >= buf->sgt->nents) {
+                        DRM_ERROR("invalid page offset\n");
+                        return -EINVAL;
+                }
+
+                pfn = __phys_to_pfn(sg_phys(sgl)) + page_offset;
+        } else {
                 if (!buf->pages)
                         return -EINTR;
 
-                pfn = page_to_pfn(buf->pages[page_offset++]);
-        } else
-                pfn = (buf->dma_addr >> PAGE_SHIFT) + page_offset;
+                pfn = page_to_pfn(buf->pages[0]) + page_offset;
+        }
 
         return vm_insert_mixed(vma, f_vaddr, pfn);
 }