gpu: ion: Add support for cached mappings that don't fault

We have found that faulting in the mappings for cached
allocations has a significant performance impact and is
only a benefit if only a small part of the buffer is
touched by the cpu (an uncommon case for software rendering).
This patch introduces a ION_FLAG_CACHED_NEEDS_SYNC
which determines whether a mapping should be created by
faulting or at mmap time.  If this flag is set,
userspace must manage the caches explictly using the SYNC ioctl.

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 3aeb41c..d1c7b84 100644 (file)
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -164,7 +164,8 @@ static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
                return ERR_PTR(PTR_ERR(table));
        }
        buffer->sg_table = table;
-       if (buffer->flags & ION_FLAG_CACHED) {
+       if (buffer->flags & ION_FLAG_CACHED &&
+           !(buffer->flags & ION_FLAG_CACHED_NEEDS_SYNC)) {
                for_each_sg(buffer->sg_table->sgl, sg, buffer->sg_table->nents,
                            i) {
                        if (sg_dma_len(sg) == PAGE_SIZE)
@@ -763,7 +764,8 @@ static void ion_buffer_sync_for_device(struct ion_buffer *buffer,
        pr_debug("%s: syncing for device %s\n", __func__,
                 dev ? dev_name(dev) : "null");
 
-       if (!(buffer->flags & ION_FLAG_CACHED))
+       if (!(buffer->flags & ION_FLAG_CACHED) ||
+           (buffer->flags & ION_FLAG_CACHED_NEEDS_SYNC))
                return;
 
        mutex_lock(&buffer->lock);
@@ -853,18 +855,22 @@ static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
                return -EINVAL;
        }
 
-       if (buffer->flags & ION_FLAG_CACHED) {
+       if (buffer->flags & ION_FLAG_CACHED &&
+           !(buffer->flags & ION_FLAG_CACHED_NEEDS_SYNC)) {
                vma->vm_private_data = buffer;
                vma->vm_ops = &ion_vma_ops;
                ion_vm_open(vma);
-       } else {
-               vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
-               mutex_lock(&buffer->lock);
-               /* now map it to userspace */
-               ret = buffer->heap->ops->map_user(buffer->heap, buffer, vma);
-               mutex_unlock(&buffer->lock);
+               return 0;
        }
 
+       if (!(buffer->flags & ION_FLAG_CACHED))
+               vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+       mutex_lock(&buffer->lock);
+       /* now map it to userspace */
+       ret = buffer->heap->ops->map_user(buffer->heap, buffer, vma);
+       mutex_unlock(&buffer->lock);
+
        if (ret)
                pr_err("%s: failure mapping buffer to userspace\n",
                       __func__);
@@ -1021,7 +1027,9 @@ static int ion_sync_for_device(struct ion_client *client, int fd)
                return -EINVAL;
        }
        buffer = dmabuf->priv;
-       ion_buffer_sync_for_device(buffer, NULL, DMA_BIDIRECTIONAL);
+
+       dma_sync_sg_for_device(NULL, buffer->sg_table->sgl,
+                              buffer->sg_table->nents, DMA_BIDIRECTIONAL);
        dma_buf_put(dmabuf);
        return 0;
 }

diff --git a/drivers/staging/android/ion/ion.h b/drivers/staging/android/ion/ion.h
index 83baa38..072d64d 100644 (file)
--- a/drivers/staging/android/ion/ion.h
+++ b/drivers/staging/android/ion/ion.h
@@ -50,6 +50,9 @@ enum ion_heap_type {
                                           cached, ion will do cache
                                           maintenance when the buffer is
                                           mapped for dma */
+#define ION_FLAG_CACHED_NEEDS_SYNC 2   /* mappings of this buffer will created
+                                          at mmap time, if this is set
+                                          caches must be managed manually */
 
 #ifdef __KERNEL__
 struct ion_device;