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SubjectRe: [PATCH] staging: android: ion: move map_kernel to ion_dma_buf_kmap
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On 12/24/18 12:19 AM, Qing Xia wrote:
> Now, as Google's user guide, if userspace need clean ION buffer's
> cache, they should call ioctl(fd, DMA_BUF_IOCTL_SYNC, sync). Then
> we found that ion_dma_buf_begin_cpu_access/ion_dma_buf_end_cpu_access
> will do ION buffer's map_kernel, it's not necessary. And if usersapce
> only need clean cache, they will call ion_dma_buf_end_cpu_access by
> dmabuf's ioctl, ION buffer's kmap_cnt will be wrong value -1, then
> driver could not get right kernel vaddr by dma_buf_kmap.
>

The problem is this subtly violates how dma_buf is supposed
to work. All setup is supposed to happen in begin_cpu_access.
I agree calling map kernel each time isn't great but I think
this needs to be worked out with dma_buf.

Thanks,
Laura

> Signed-off-by: Qing Xia <saberlily.xia@hisilicon.com>
> ---
> drivers/staging/android/ion/ion.c | 46 ++++++++++++++++++---------------------
> 1 file changed, 21 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index 9907332..f7e2812 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -303,45 +303,47 @@ static void ion_dma_buf_release(struct dma_buf *dmabuf)
> static void *ion_dma_buf_kmap(struct dma_buf *dmabuf, unsigned long offset)
> {
> struct ion_buffer *buffer = dmabuf->priv;
> + void *vaddr;
>
> - return buffer->vaddr + offset * PAGE_SIZE;
> + if (buffer->heap->ops->map_kernel) {
> + mutex_lock(&buffer->lock);
> + vaddr = ion_buffer_kmap_get(buffer);
> + mutex_unlock(&buffer->lock);
> + if (IS_ERR(vaddr))
> + return vaddr;
> +
> + return vaddr + offset * PAGE_SIZE;
> + }
> +
> + return NULL;
> }
>
> static void ion_dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long offset,
> void *ptr)
> {
> + struct ion_buffer *buffer = dmabuf->priv;
> +
> + if (buffer->heap->ops->map_kernel) {
> + mutex_lock(&buffer->lock);
> + ion_buffer_kmap_put(buffer);
> + mutex_unlock(&buffer->lock);
> + }
> }
>
> static int ion_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
> enum dma_data_direction direction)
> {
> struct ion_buffer *buffer = dmabuf->priv;
> - void *vaddr;
> struct ion_dma_buf_attachment *a;
> - int ret = 0;
> -
> - /*
> - * TODO: Move this elsewhere because we don't always need a vaddr
> - */
> - if (buffer->heap->ops->map_kernel) {
> - mutex_lock(&buffer->lock);
> - vaddr = ion_buffer_kmap_get(buffer);
> - if (IS_ERR(vaddr)) {
> - ret = PTR_ERR(vaddr);
> - goto unlock;
> - }
> - mutex_unlock(&buffer->lock);
> - }
>
> mutex_lock(&buffer->lock);
> list_for_each_entry(a, &buffer->attachments, list) {
> dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents,
> direction);
> }
> -
> -unlock:
> mutex_unlock(&buffer->lock);
> - return ret;
> +
> + return 0;
> }
>
> static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
> @@ -350,12 +352,6 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
> struct ion_buffer *buffer = dmabuf->priv;
> struct ion_dma_buf_attachment *a;
>
> - if (buffer->heap->ops->map_kernel) {
> - mutex_lock(&buffer->lock);
> - ion_buffer_kmap_put(buffer);
> - mutex_unlock(&buffer->lock);
> - }
> -
> mutex_lock(&buffer->lock);
> list_for_each_entry(a, &buffer->attachments, list) {
> dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents,
>

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