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Commit 856661d5 authored by Rebecca Schultz Zavin's avatar Rebecca Schultz Zavin Committed by Greg Kroah-Hartman
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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: default avatarRebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d3c0bced

drivers/staging/android/ion/ion.c

+18 −10
Original line number Diff line number Diff line
@@ -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);
@@ -853,17 +855,21 @@ 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 {

		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",
@@ -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;

}

drivers/staging/android/ion/ion.h

+3 −0
Original line number Diff line number Diff line
@@ -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;