[PATCH 6.6.y] PCI: dwc: Set DMA_BYPASS bit in outbound IATU CTRL2 register

[Sasha Levin <sashal@kernel.org>]

From: Sumit Kumar <sumit.kumar@oss.qualcomm.com>

[ Upstream commit efadda401c5c8e2390ba66508eba154dbd0db5a9 ]

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
[ sashal: adapted the outbound control update to the older helper by initializing val from PCIE_ATU_ENABLE before writing CTRL2 ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/controller/dwc/pcie-designware.c | 5 ++++-
 drivers/pci/controller/dwc/pcie-designware.h | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 504450a8b6a45..86326116d85ca 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -506,7 +506,10 @@ static int __dw_pcie_prog_outbound_atu(struct dw_pcie *pci, u8 func_no,
 		val = dw_pcie_enable_ecrc(val);
 	dw_pcie_writel_atu_ob(pci, index, PCIE_ATU_REGION_CTRL1, val);
 
-	dw_pcie_writel_atu_ob(pci, index, PCIE_ATU_REGION_CTRL2, PCIE_ATU_ENABLE);
+	val = PCIE_ATU_ENABLE;
+	if (dw_pcie_ver_is_ge(pci, 460A))
+		val |= PCIE_ATU_DMA_BYPASS;
+	dw_pcie_writel_atu_ob(pci, index, PCIE_ATU_REGION_CTRL2, val);
 
 	/*
 	 * Make sure ATU enable takes effect before any subsequent config
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 1ffa31797a17c..bb481205e23b5 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -154,6 +154,7 @@
 #define PCIE_ATU_REGION_CTRL2		0x004
 #define PCIE_ATU_ENABLE			BIT(31)
 #define PCIE_ATU_BAR_MODE_ENABLE	BIT(30)
+#define PCIE_ATU_DMA_BYPASS		BIT(27)
 #define PCIE_ATU_FUNC_NUM_MATCH_EN      BIT(19)
 #define PCIE_ATU_LOWER_BASE		0x008
 #define PCIE_ATU_UPPER_BASE		0x00C
-- 
2.53.0