[PATCH v3 5/6] iommu/mediatek: Add mt8173 IOMMU driver
From: robin.murphy@arm.com (Robin Murphy)
Date: 2015-07-27 15:49:37
Also in:
linux-devicetree, linux-iommu, linux-mediatek, lkml
On 27/07/15 16:31, Russell King - ARM Linux wrote:
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... Robin.