Subject: [PATCH] iommu/mediatek: Move the tlb_sync into tlb_flush

From: Yong Wu <[email-masked]>
Date: Mon, 30 Sep 2019 13:42:22 +0800

The commit 4d689b619445 ("iommu/io-pgtable-arm-v7s: Convert to IOMMU API
TLB sync") help move the tlb_sync of unmap from v7s into the iommu
framework. It helps add a new function "mtk_iommu_iotlb_sync", But it
lacked the dom->pgtlock, then it will cause the variable
"tlb_flush_active" may be changed unexpectedly, we could see this warning
log randomly:

mtk-iommu 10205000.iommu: Partial TLB flush timed out, falling back to
full flush

To fix this issue, we can add dom->pgtlock in the "mtk_iommu_iotlb_sync".
And when checking this issue, we find that __arm_v7s_unmap call
io_pgtable_tlb_add_flush consecutively when it is supersection/largepage,
this also is potential unsafe for us. There is no tlb flush queue in the
MediaTek M4U HW. The HW always expect the tlb_flush/tlb_sync one by one.
If v7s don't always gurarantee the sequence, Thus, In this patch I move
the tlb_sync into tlb_flush(also rename the function deleting "_nosync").
and we don't care if it is leaf, rearrange the callback functions. Also,
the tlb flush/sync was already finished in v7s, then iotlb_sync and
iotlb_sync_all is unnecessary.

Besides, there are two minor changes:
a) Use writel for the register F_MMU_INV_RANGE which is for triggering the
HW work. We expect all the setting(iova_start/iova_end...) have already
been finished before F_MMU_INV_RANGE.
b) Reduce the tlb timeout value from 100000us to 1000us. the original value
is so long that affect the multimedia performance.

Fixes: 4d689b619445 ("iommu/io-pgtable-arm-v7s: Convert to IOMMU API TLB sync")
Signed-off-by: Chao Hao <[email-masked]>
Signed-off-by: Yong Wu <[email-masked]>
---
This patch looks break the logic for tlb_flush and tlb_sync. I'm not
sure if it
is reasonable. If someone has concern, I could change:
a) Add dom->pgtlock in the mtk_iommu_iotlb_sync
b) Add a io_pgtable_tlb_sync in [1].

[1]
https://elixir.bootlin.com/linux/v5.3-rc1/source/drivers/iommu/io-pgtable-arm-v7s.c#L655

This patch rebase on Joerg's mediatek-smmu-merge branch which has mt8183
and Will's "Rework IOMMU API to allow for batching of invalidation".
---
 drivers/iommu/mtk_iommu.c | 74 ++++++++++++-----------------------------------
 drivers/iommu/mtk_iommu.h |  1 -
 2 files changed, 19 insertions(+), 56 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 6066272..e13cc56 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -173,11 +173,12 @@ static void mtk_iommu_tlb_flush_all(void *cookie)
 	}
 }
 
-static void mtk_iommu_tlb_add_flush_nosync(unsigned long iova, size_t size,
-					   size_t granule, bool leaf,
-					   void *cookie)
+static void mtk_iommu_tlb_add_flush(unsigned long iova, size_t size,
+				    size_t granule, void *cookie)
 {
 	struct mtk_iommu_data *data = cookie;
+	int ret;
+	u32 tmp;
 
 	for_each_m4u(data) {
 		writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
@@ -186,25 +187,15 @@ static void mtk_iommu_tlb_add_flush_nosync(unsigned long iova, size_t size,
 		writel_relaxed(iova, data->base + REG_MMU_INVLD_START_A);
 		writel_relaxed(iova + size - 1,
 			       data->base + REG_MMU_INVLD_END_A);
-		writel_relaxed(F_MMU_INV_RANGE,
-			       data->base + REG_MMU_INVALIDATE);
-		data->tlb_flush_active = true;
-	}
-}
-
-static void mtk_iommu_tlb_sync(void *cookie)
-{
-	struct mtk_iommu_data *data = cookie;
-	int ret;
-	u32 tmp;
-
-	for_each_m4u(data) {
-		/* Avoid timing out if there's nothing to wait for */
-		if (!data->tlb_flush_active)
-			return;
+		writel(F_MMU_INV_RANGE, data->base + REG_MMU_INVALIDATE);
 
+		/*
+		 * There is no tlb flush queue in the HW, the HW always expect
+		 * tlb_flush and tlb_sync one by one. Here tlb_sync always
+		 * follows tlb_flush to avoid break the sequence.
+		 */
 		ret = readl_poll_timeout_atomic(data->base + REG_MMU_CPE_DONE,
-						tmp, tmp != 0, 10, 100000);
+						tmp, tmp != 0, 10, 1000);
 		if (ret) {
 			dev_warn(data->dev,
 				 "Partial TLB flush timed out, falling back to full flush\n");
@@ -212,36 +203,21 @@ static void mtk_iommu_tlb_sync(void *cookie)
 		}
 		/* Clear the CPE status */
 		writel_relaxed(0, data->base + REG_MMU_CPE_DONE);
-		data->tlb_flush_active = false;
 	}
 }
 
-static void mtk_iommu_tlb_flush_walk(unsigned long iova, size_t size,
-				     size_t granule, void *cookie)
+static void mtk_iommu_tlb_flush_page(struct iommu_iotlb_gather *gather,
+				     unsigned long iova, size_t granule,
+				     void *cookie)
 {
-	mtk_iommu_tlb_add_flush_nosync(iova, size, granule, false, cookie);
-	mtk_iommu_tlb_sync(cookie);
-}
-
-static void mtk_iommu_tlb_flush_leaf(unsigned long iova, size_t size,
-				     size_t granule, void *cookie)
-{
-	mtk_iommu_tlb_add_flush_nosync(iova, size, granule, true, cookie);
-	mtk_iommu_tlb_sync(cookie);
-}
-
-static void mtk_iommu_tlb_flush_page_nosync(struct iommu_iotlb_gather *gather,
-					    unsigned long iova, size_t granule,
-					    void *cookie)
-{
-	mtk_iommu_tlb_add_flush_nosync(iova, granule, granule, true, cookie);
+	mtk_iommu_tlb_add_flush(iova, granule, granule, cookie);
 }
 
 static const struct iommu_flush_ops mtk_iommu_flush_ops = {
 	.tlb_flush_all = mtk_iommu_tlb_flush_all,
-	.tlb_flush_walk = mtk_iommu_tlb_flush_walk,
-	.tlb_flush_leaf = mtk_iommu_tlb_flush_leaf,
-	.tlb_add_page = mtk_iommu_tlb_flush_page_nosync,
+	.tlb_flush_walk = mtk_iommu_tlb_add_flush,
+	.tlb_flush_leaf = mtk_iommu_tlb_add_flush,
+	.tlb_add_page = mtk_iommu_tlb_flush_page,
 };
 
 static irqreturn_t mtk_iommu_isr(int irq, void *dev_id)
@@ -445,17 +421,6 @@ static size_t mtk_iommu_unmap(struct iommu_domain *domain,
 	return unmapsz;
 }
 
-static void mtk_iommu_flush_iotlb_all(struct iommu_domain *domain)
-{
-	mtk_iommu_tlb_sync(mtk_iommu_get_m4u_data());
-}
-
-static void mtk_iommu_iotlb_sync(struct iommu_domain *domain,
-				 struct iommu_iotlb_gather *gather)
-{
-	mtk_iommu_tlb_sync(mtk_iommu_get_m4u_data());
-}
-
 static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
 					  dma_addr_t iova)
 {
@@ -574,8 +539,7 @@ static int mtk_iommu_of_xlate(struct device *dev, struct of_phandle_args *args)
 	.detach_dev	= mtk_iommu_detach_device,
 	.map		= mtk_iommu_map,
 	.unmap		= mtk_iommu_unmap,
-	.flush_iotlb_all = mtk_iommu_flush_iotlb_all,
-	.iotlb_sync	= mtk_iommu_iotlb_sync,
+	/* No iotlb_sync here since the tlb_sync always follows the tlb_flush */
 	.iova_to_phys	= mtk_iommu_iova_to_phys,
 	.add_device	= mtk_iommu_add_device,
 	.remove_device	= mtk_iommu_remove_device,
diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
index fc0f16e..24712f5 100644
--- a/drivers/iommu/mtk_iommu.h
+++ b/drivers/iommu/mtk_iommu.h
@@ -57,7 +57,6 @@ struct mtk_iommu_data {
 	struct mtk_iommu_domain		*m4u_dom;
 	struct iommu_group		*m4u_group;
 	bool                            enable_4GB;
-	bool				tlb_flush_active;
 
 	struct iommu_device		iommu;
 	const struct mtk_iommu_plat_data *plat_data;
-- 
1.9.1

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