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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        =?UTF-8?q?Marek=20Beh=C3=BAn?= <kabel@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
        Sasha Levin <sashal@kernel.org>
Subject: =?UTF-8?q?=5BPATCH=206=2E0=20659/862=5D=20=3D=3FUTF-8=3Fq=3FARM/dma-mapp=3DD1=3D96ng=3A=3D20dont=3D20override=3D20-=3Edma=3D5Fcohe=3F=3D=20=3D=3FUTF-8=3Fq=3Frent=3D20when=3D20set=3D20from=3D20a=3D20bus=3D20notifier=3F=3D?=
Date:   Wed, 19 Oct 2022 10:32:26 +0200
Message-Id: <20221019083319.087440003@linuxfoundation.org>
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From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 49bc8bebae79c8516cb12f91818f3a7907e3ebce ]

Commit ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
caused a regression on the mvebu platform, wherein devices that are
dma-coherent are marked as dma-noncoherent, because although
mvebu_hwcc_notifier() after that commit still marks then as coherent,
the arm_coherent_dma_ops() function, which is called later, overwrites
this setting, since it is being called from drivers/of/device.c with
coherency parameter determined by of_dma_is_coherent(), and the
device-trees do not declare the 'dma-coherent' property.

Fix this by defaulting never clearing the dma_coherent flag in
arm_coherent_dma_ops().

Fixes: ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
Reported-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Tested-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/arm/mm/dma-mapping.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 089c9c644cce..bfc7476f1411 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1769,8 +1769,16 @@ static void arm_teardown_iommu_dma_ops(struct device *dev) { }
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-	dev->archdata.dma_coherent = coherent;
-	dev->dma_coherent = coherent;
+	/*
+	 * Due to legacy code that sets the ->dma_coherent flag from a bus
+	 * notifier we can't just assign coherent to the ->dma_coherent flag
+	 * here, but instead have to make sure we only set but never clear it
+	 * for now.
+	 */
+	if (coherent) {
+		dev->archdata.dma_coherent = true;
+		dev->dma_coherent = true;
+	}
 
 	/*
 	 * Don't override the dma_ops if they have already been set. Ideally
-- 
2.35.1