On Thu, 2015-06-18 at 17:54 +0100, Robin Murphy wrote:

On 18/06/15 16:00, Yong Wu wrote:

quoted

Hi Robin,
     while our drm test, we meet a problem while dma-mmap.

  On Thu, 2015-06-11 at 16:54 +0100, Robin Murphy wrote:

quoted

Taking inspiration from the existing arch/arm code, break out some
generic functions to interface the DMA-API to the IOMMU-API. This will
do the bulk of the heavy lifting for IOMMU-backed dma-mapping.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
  drivers/iommu/Kconfig     |   7 +
  drivers/iommu/Makefile    |   1 +
  drivers/iommu/dma-iommu.c | 560 ++++++++++++++++++++++++++++++++++++++++++++++
  include/linux/dma-iommu.h |  94 ++++++++
  4 files changed, 662 insertions(+)
  create mode 100644 drivers/iommu/dma-iommu.c
  create mode 100644 include/linux/dma-iommu.h

[snip]

quoted

+/**
+ * iommu_dma_mmap - Map a buffer into provided user VMA
+ * @pages: Array representing buffer from iommu_dma_alloc()
+ * @size: Size of buffer in bytes
+ * @vma: VMA describing requested userspace mapping
+ *
+ * Maps the pages of the buffer in @pages into @vma. The caller is responsible
+ * for verifying the correct size and protection of @vma beforehand.
+ */
+
+int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma)
+{
+	unsigned long uaddr = vma->vm_start;
+	unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	int ret = -ENXIO;
+
+	for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {

Is it :  for (i = 0; i < count && uaddr < vma->vm_end; i++)

According to the patches at [1], respecting vma->pgoff is necessary for 
users who only want to mmap part of the buffer. Does your DRM driver by 
any chance need the same fix as the Rockchip one?

Thanks. We will try to add it.

quoted

quoted

+		ret = vm_insert_page(vma, uaddr, pages[i]);
+		if (ret)
+			break;
+		uaddr += PAGE_SIZE;
+	}
+	return ret;
+}
+

And to save another email:

 >> +	if (WARN_ON(!area || area->pages))
 > Is it:    if (WARN_ON(!area || !area->pages))
 >> +		return -ENXIO;

You're absolutely right, thanks. I've got a couple more bugfixes in 
progress too, so I'll try to get an updated branch pushed out soon; I'll 
hold off posting a v3 to the list until after the upcoming merge window, 
though.

Robin.

[1]:http://thread.gmane.org/gmane.linux.kernel/1932343