[PATCH 031/115] gpu: ion: Add support for cached mappings that don't fault

John Stultz
2013-12-13T22:26:57Z

From: Rebecca Schultz Zavin <rebecca@android.com>

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>
---
drivers/staging/android/ion/ion.c | 28 ++++++++++++++++++----------
drivers/staging/android/ion/ion.h | 3 +++
2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 3aeb41c..d1c7b84 100644
--- 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
--- 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;
--
1.8.3.2