On Fri, May 15, 2015 at 10:43:28AM +0100, Yong Wu wrote:

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

After looking at the page table code, I thought I'd come and check your
TLB invalidate code here.

+static void mtk_iommu_tlb_flush_all(void *cookie)
+{
+       struct mtk_iommu_domain *domain = cookie;
+       u32 val;
+
+       val = F_INVLD_EN1 | F_INVLD_EN0;
+       writel(val, domain->imuinfo->base + REG_MMU_INV_SEL);
+       writel(F_ALL_INVLD, domain->imuinfo->base + REG_MMU_INVALIDATE);
+}
+
+static void mtk_iommu_tlb_add_flush(unsigned long iova, size_t size,
+                                   bool leaf, void *cookie)
+{
+       struct mtk_iommu_domain *domain = cookie;
+       void __iomem *m4u_base = domain->imuinfo->base;
+       unsigned int iova_start = iova, iova_end = iova + size - 1;
+       int ret;
+       u32 val;
+
+       val = F_INVLD_EN1 | F_INVLD_EN0;
+       writel(val, m4u_base + REG_MMU_INV_SEL);
+
+       writel(iova_start, m4u_base + REG_MMU_INVLD_START_A);
+       writel(iova_end, m4u_base + REG_MMU_INVLD_END_A);
+       writel(F_MMU_INV_RANGE, m4u_base + REG_MMU_INVALIDATE);
+
+       ret = readl_poll_timeout_atomic(m4u_base + REG_MMU_CPE_DONE, val,
+                                       val != 0, 10, 1000000);
+       if (ret) {
+               dev_warn(domain->imuinfo->dev, "Invalid tlb don't done\n");
+               mtk_iommu_tlb_flush_all(cookie);
+       }
+       writel(0, m4u_base + REG_MMU_CPE_DONE);
+}

You don't need to wait for completion here if you can implement a proper
->tlb_sync callback.

+static void mtk_iommu_flush_pgtable(void *ptr, size_t size, void *cookie)
+{
+       /*
+        * After delete arch_setup_dma_ops,
+        * This will be replaced with dma_map_page
+        */
+        __dma_flush_range(ptr, ptr + size);
+}

This should give you the necessary barriers to ensure visibility of the
updated page tables, so you can use the _relaxed io accessors for the
other TLB functions.

+static struct iommu_gather_ops mtk_iommu_gather_ops = {
+       .tlb_flush_all = mtk_iommu_tlb_flush_all,
+       .tlb_add_flush = mtk_iommu_tlb_add_flush,
+       .tlb_sync = mtk_iommu_tlb_flush_all,

sync isn't required to flush anything; it's just supposed to wait for
any outstanding invalidation (i.e. from tlb_add_flush) to complete.

Will