ion: fix bugs in cma heap

Implement ion_cma_unmap_kernel, ion will call it unconditionally.
Use correct gfp flags when calling dma_alloc_coherent so it doesn't
try to use atomic DMA memory.
Check for invalid alignment when allocating.
Reject cached allocations - the cpu address returned by
dma_alloc_coherent is always going to be an uncached mapping, so
map_kernel will not see data written by a cached userspace mapping.

Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_cma_heap.c

@@ -69,13 +69,20 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 
 	dev_dbg(dev, "Request buffer allocation len %ld\n", len);
 
+	if (buffer->flags & ION_FLAG_CACHED)
+		return -EINVAL;
+
+	if (align > PAGE_SIZE)
+		return -EINVAL;
+
 	info = kzalloc(sizeof(struct ion_cma_buffer_info), GFP_KERNEL);
 	if (!info) {
 		dev_err(dev, "Can't allocate buffer info\n");
 		return ION_CMA_ALLOCATE_FAILED;
 	}
 
-	info->cpu_addr = dma_alloc_coherent(dev, len, &(info->handle), 0);
+	info->cpu_addr = dma_alloc_coherent(dev, len, &(info->handle),
+						GFP_HIGHUSER | __GFP_ZERO);
 
 	if (!info->cpu_addr) {
 		dev_err(dev, "Fail to allocate buffer\n");
@@ -170,6 +177,11 @@ static void *ion_cma_map_kernel(struct ion_heap *heap,
 	return info->cpu_addr;
 }
 
+static void ion_cma_unmap_kernel(struct ion_heap *heap,
+					struct ion_buffer *buffer)
+{
+}
+
 static struct ion_heap_ops ion_cma_ops = {
 	.allocate = ion_cma_allocate,
 	.free = ion_cma_free,
@@ -178,6 +190,7 @@ static struct ion_heap_ops ion_cma_ops = {
 	.phys = ion_cma_phys,
 	.map_user = ion_cma_mmap,
 	.map_kernel = ion_cma_map_kernel,
+	.unmap_kernel = ion_cma_unmap_kernel,
 };
 
 struct ion_heap *ion_cma_heap_create(struct ion_platform_heap *data)