linux-kernel - [PATCH v2 5/8] dma-mapping: Support batch mode for dma_direct_sync_sg_for

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Message-ID: <20251226225254.46197-6-21cnbao@gmail.com>
Date: Sat, 27 Dec 2025 11:52:45 +1300
From: Barry Song <21cnbao@...il.com>
To: catalin.marinas@....com,
	m.szyprowski@...sung.com,
	robin.murphy@....com,
	will@...nel.org,
	iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org,
	Barry Song <baohua@...nel.org>,
	Leon Romanovsky <leon@...nel.org>,
	Ada Couprie Diaz <ada.coupriediaz@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Marc Zyngier <maz@...nel.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ryan Roberts <ryan.roberts@....com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Tangquan Zheng <zhengtangquan@...o.com>
Subject: [PATCH v2 5/8] dma-mapping: Support batch mode for dma_direct_sync_sg_for_*

From: Barry Song <baohua@...nel.org>

Instead of performing a flush per SG entry, issue all cache
operations first and then flush once. This ultimately benefits
__dma_sync_sg_for_cpu() and __dma_sync_sg_for_device().

Cc: Leon Romanovsky <leon@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Ada Couprie Diaz <ada.coupriediaz@....com>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: Suren Baghdasaryan <surenb@...gle.com>
Cc: Tangquan Zheng <zhengtangquan@...o.com>
Signed-off-by: Barry Song <baohua@...nel.org>
---
 kernel/dma/direct.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index a219911c7b90..98bacf562ca1 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -402,12 +402,12 @@ void dma_direct_sync_sg_for_device(struct device *dev,
 
 		swiotlb_sync_single_for_device(dev, paddr, sg->length, dir);
 
-		if (!dev_is_dma_coherent(dev)) {
+		if (!dev_is_dma_coherent(dev))
 			arch_sync_dma_for_device(paddr, sg->length,
 					dir);
-			arch_sync_dma_flush();
-		}
 	}
+	if (!dev_is_dma_coherent(dev))
+		arch_sync_dma_flush();
 }
 #endif
 
@@ -423,10 +423,8 @@ void dma_direct_sync_sg_for_cpu(struct device *dev,
 	for_each_sg(sgl, sg, nents, i) {
 		phys_addr_t paddr = dma_to_phys(dev, sg_dma_address(sg));
 
-		if (!dev_is_dma_coherent(dev)) {
+		if (!dev_is_dma_coherent(dev))
 			arch_sync_dma_for_cpu(paddr, sg->length, dir);
-			arch_sync_dma_flush();
-		}
 
 		swiotlb_sync_single_for_cpu(dev, paddr, sg->length, dir);
 
@@ -434,8 +432,10 @@ void dma_direct_sync_sg_for_cpu(struct device *dev,
 			arch_dma_mark_clean(paddr, sg->length);
 	}
 
-	if (!dev_is_dma_coherent(dev))
+	if (!dev_is_dma_coherent(dev)) {
+		arch_sync_dma_flush();
 		arch_sync_dma_for_cpu_all();
+	}
 }
 
 /*
-- 
2.43.0