drm/vgem: fix cache synchronization on arm/arm64

drm_cflush_pages() is no-op on arm/arm64.  But instead we can use
dma_sync API.

Fixes failures w/ vgem_test.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190717211542.30482-1-robdclark@gmail.com

diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index 11a8f99ba18c5f007734abef1003cc44d5e778a1..fc04803ff40355dfda54ef2eb6057e903a7dc1ce 100644 (file)
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -47,10 +47,16 @@ static struct vgem_device {
        struct platform_device *platform;
 } *vgem_device;
 
+static void sync_and_unpin(struct drm_vgem_gem_object *bo);
+static struct page **pin_and_sync(struct drm_vgem_gem_object *bo);
+
 static void vgem_gem_free_object(struct drm_gem_object *obj)
 {
        struct drm_vgem_gem_object *vgem_obj = to_vgem_bo(obj);
 
+       if (!obj->import_attach)
+               sync_and_unpin(vgem_obj);
+
        kvfree(vgem_obj->pages);
        mutex_destroy(&vgem_obj->pages_lock);
 
@@ -78,40 +84,15 @@ static vm_fault_t vgem_gem_fault(struct vm_fault *vmf)
                return VM_FAULT_SIGBUS;
 
        mutex_lock(&obj->pages_lock);
+       if (!obj->pages)
+               pin_and_sync(obj);
        if (obj->pages) {
                get_page(obj->pages[page_offset]);
                vmf->page = obj->pages[page_offset];
                ret = 0;
        }
        mutex_unlock(&obj->pages_lock);
-       if (ret) {
-               struct page *page;
-
-               page = shmem_read_mapping_page(
-                                       file_inode(obj->base.filp)->i_mapping,
-                                       page_offset);
-               if (!IS_ERR(page)) {
-                       vmf->page = page;
-                       ret = 0;
-               } else switch (PTR_ERR(page)) {
-                       case -ENOSPC:
-                       case -ENOMEM:
-                               ret = VM_FAULT_OOM;
-                               break;
-                       case -EBUSY:
-                               ret = VM_FAULT_RETRY;
-                               break;
-                       case -EFAULT:
-                       case -EINVAL:
-                               ret = VM_FAULT_SIGBUS;
-                               break;
-                       default:
-                               WARN_ON(PTR_ERR(page));
-                               ret = VM_FAULT_SIGBUS;
-                               break;
-               }
 
-       }
        return ret;
 }
 
@@ -277,32 +258,93 @@ static const struct file_operations vgem_driver_fops = {
        .release        = drm_release,
 };
 
-static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
+/* Called under pages_lock, except in free path (where it can't race): */
+static void sync_and_unpin(struct drm_vgem_gem_object *bo)
 {
-       mutex_lock(&bo->pages_lock);
-       if (bo->pages_pin_count++ == 0) {
-               struct page **pages;
+       struct drm_device *dev = bo->base.dev;
+
+       if (bo->table) {
+               dma_sync_sg_for_cpu(dev->dev, bo->table->sgl,
+                               bo->table->nents, DMA_BIDIRECTIONAL);
+               sg_free_table(bo->table);
+               kfree(bo->table);
+               bo->table = NULL;
+       }
+
+       if (bo->pages) {
+               drm_gem_put_pages(&bo->base, bo->pages, true, true);
+               bo->pages = NULL;
+       }
+}
+
+static struct page **pin_and_sync(struct drm_vgem_gem_object *bo)
+{
+       struct drm_device *dev = bo->base.dev;
+       int npages = bo->base.size >> PAGE_SHIFT;
+       struct page **pages;
+       struct sg_table *sgt;
+
+       WARN_ON(!mutex_is_locked(&bo->pages_lock));
+
+       pages = drm_gem_get_pages(&bo->base);
+       if (IS_ERR(pages)) {
+               bo->pages_pin_count--;
+               mutex_unlock(&bo->pages_lock);
+               return pages;
+       }
 
-               pages = drm_gem_get_pages(&bo->base);
-               if (IS_ERR(pages)) {
-                       bo->pages_pin_count--;
-                       mutex_unlock(&bo->pages_lock);
-                       return pages;
-               }
+       sgt = drm_prime_pages_to_sg(pages, npages);
+       if (IS_ERR(sgt)) {
+               dev_err(dev->dev,
+                       "failed to allocate sgt: %ld\n",
+                       PTR_ERR(bo->table));
+               drm_gem_put_pages(&bo->base, pages, false, false);
+               mutex_unlock(&bo->pages_lock);
+               return ERR_CAST(bo->table);
+       }
+
+       /*
+        * Flush the object from the CPU cache so that importers
+        * can rely on coherent indirect access via the exported
+        * dma-address.
+        */
+       dma_sync_sg_for_device(dev->dev, sgt->sgl,
+                       sgt->nents, DMA_BIDIRECTIONAL);
+
+       bo->pages = pages;
+       bo->table = sgt;
+
+       return pages;
+}
+
+static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
+{
+       struct page **pages;
 
-               bo->pages = pages;
+       mutex_lock(&bo->pages_lock);
+       if (bo->pages_pin_count++ == 0 && !bo->pages) {
+               pages = pin_and_sync(bo);
+       } else {
+               WARN_ON(!bo->pages);
+               pages = bo->pages;
        }
        mutex_unlock(&bo->pages_lock);
 
-       return bo->pages;
+       return pages;
 }
 
 static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
 {
+       /*
+        * We shouldn't hit this for imported bo's.. in the import
+        * case we don't own the scatter-table
+        */
+       WARN_ON(bo->base.import_attach);
+
        mutex_lock(&bo->pages_lock);
        if (--bo->pages_pin_count == 0) {
-               drm_gem_put_pages(&bo->base, bo->pages, true, true);
-               bo->pages = NULL;
+               WARN_ON(!bo->table);
+               sync_and_unpin(bo);
        }
        mutex_unlock(&bo->pages_lock);
 }
@@ -310,18 +352,12 @@ static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
 static int vgem_prime_pin(struct drm_gem_object *obj)
 {
        struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
-       long n_pages = obj->size >> PAGE_SHIFT;
        struct page **pages;
 
        pages = vgem_pin_pages(bo);
        if (IS_ERR(pages))
                return PTR_ERR(pages);
 
-       /* Flush the object from the CPU cache so that importers can rely
-        * on coherent indirect access via the exported dma-address.
-        */
-       drm_clflush_pages(pages, n_pages);
-
        return 0;
 }