FAILED: patch "[PATCH] PCI: dwc: Set DMA_BYPASS bit in outbound IATU CTRL2 register" failed to apply to 6.12-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x efadda401c5c8e2390ba66508eba154dbd0db5a9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107052243-failed-6.12-efadda401c5c@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From efadda401c5c8e2390ba66508eba154dbd0db5a9 Mon Sep 17 00:00:00 2001
From: Sumit Kumar <sumit.kumar@oss.qualcomm.com>
Date: Tue, 8 Sep 2026 11:48:22 +0530
Subject: [PATCH] PCI: dwc: Set DMA_BYPASS bit in outbound IATU CTRL2 register

An outbound iATU region matches any local (AXI/application-side)
address that falls within its Base/Limit window and rewrites it to
the PCIe-side address programmed in that region's Target Address
Registers before the transaction goes out on the link. This matching
does not distinguish CPU-initiated transactions from ones issued by
the internal DMA engine (eDMA/HDMA).

Example: outbound region 0 is programmed with Base/Limit covering
local addresses 0x8000_0000-0x8000_0FFF and Target 0x1_0000_0000, for
CPU-initiated accesses. The DMA engine is later given a descriptor
whose destination is the host address 0x8000_0080, which happens to
fall inside region 0's Base/Limit range. The iATU matches the DMA
transaction against region 0 too and rewrites it to 0x1_0000_0080
instead of passing 0x8000_0080 through unchanged. The transaction
then lands on the wrong host address, causing data corruption or an
IOMMU fault when the rewritten address has no valid mapping.

Set the DMA_BYPASS bit (bit 27) in PCIE_ATU_REGION_CTRL2 when
programming outbound iATU regions so only CPU/AXI-initiated
transactions are matched against the region; DMA engine transactions
bypass the translation and go out on the PCIe link with their
original address.

Signed-off-by: Sumit Kumar <sumit.kumar@oss.qualcomm.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260908-dma_bypass-v2-1-c3c81d408c0c@oss.qualcomm.com
---
 drivers/pci/controller/dwc/pcie-designware.c | 2 ++
 drivers/pci/controller/dwc/pcie-designware.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 855d2a54b3c6b..074b007dc2963 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -577,6 +577,8 @@ int dw_pcie_prog_outbound_atu(struct dw_pcie *pci,
 		/* The data-less messages only for now */
 		val |= ATU_INHIBIT_PAYLOAD | atu->code;
 	}
+	if (dw_pcie_ver_is_ge(pci, 460A))
+		val |= ATU_DMA_BYPASS;
 	dw_pcie_writel_atu_ob(pci, atu->index, ATU_REGION_CTRL2, val);
 
 	/*
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index aea474ad803cd..61e9c4e979af6 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -217,6 +217,7 @@
 #define  ATU_ENABLE			BIT(31)
 #define  ATU_BAR_MODE_ENABLE		BIT(30)
 #define  ATU_CFG_SHIFT_MODE_ENABLE	BIT(28)
+#define  ATU_DMA_BYPASS			BIT(27)
 #define  ATU_INHIBIT_PAYLOAD		BIT(22)
 #define  ATU_FUNC_NUM_MATCH_EN		BIT(19)
 #define ATU_LOWER_BASE			0x008
-- 
2.53.0