Re: [PATCH] staging: android: ion: move map_kernel to ion_dma_buf_kmap

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On 2019/1/3 6:36, Laura Abbott wrote:
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

Thanks for your explanation.

Signed-off-by: Qing Xia <saberlily.xia@xxxxxxxxxxxxx>
---
  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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