On 27/07/15 16:31, Russell King - ARM Linux wrote:
On Mon, Jul 27, 2015 at 02:23:26PM +0100, Robin Murphy wrote:
On 16/07/15 10:04, Yong Wu wrote:
This patch adds support for mediatek m4u (MultiMedia Memory Management
Unit).
Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
[...]
+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...
Robin.
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