On Mon, 2015-07-27 at 16:49 +0100, Robin Murphy wrote:

On 27/07/15 16:31, Russell King - ARM Linux wrote:

quoted

On Mon, Jul 27, 2015 at 02:23:26PM +0100, Robin Murphy wrote:

quoted

On 16/07/15 10:04, Yong Wu wrote:

quoted

This patch adds support for mediatek m4u (MultiMedia Memory Management
Unit).

Signed-off-by: Yong Wu <yong.wu@mediatek.com>

[...]

quoted

+static void mtk_iommu_flush_pgtable(void *ptr, size_t size, void *cookie)
+{
+       struct mtk_iommu_domain *domain = cookie;
+       unsigned long offset = (unsigned long)ptr & ~PAGE_MASK;
+
+       dma_map_page(domain->data->dev, virt_to_page(ptr), offset,
+                    size, DMA_TO_DEVICE);

Nit: this looks like it may as well be dma_map_single.

It would probably be worth following it with a matching unmap too, just to
avoid any possible leakage bugs (especially if this M4U ever appears in a
SoC supporting RAM above the 32-bit boundary).

Why not do the job properly?  Take a look at how I implemented the
streaming DMA API on Tegra SMMU (patch set recently sent out earlier
today).

There's no need for hacks like dma_map_page() (and discarding it's
return value) or dma_map_page() followed by dma_unmap_page().

Indeed, as it happens I do have a branch where I prototyped that for the 
long-descriptor io-pgtable-arm code a while ago; this discussion has 
prompted me to dig it up again. Stay tuned, folks...

Hi Russell, Robin,

     From I see in arm-smmu-v3.c in v4.2-rc1, 
     
     The flush_pgtable seems like this:
//==========
	dma_addr_t dma_addr;

	dma_addr = dma_map_page(dev, ptr, size, DMA_TO_DEVICE);

	if (dma_mapping_error(dev, dma_addr))
		dev_err(dev, "failed to flush pgtable at %p\n", ptr);
	else
		dma_unmap_page(dev, dma_addr, size, DMA_TO_DEVICE);
//==========
       I will change map like this and use dma_map_single instead.

       Is this also seems to be not proper?

       Then how to do it?  add this before unmap? :
       dma_sync_single_for_device(dev, dma_addr, size, DMA_TO_DEVICE);

Robin.