ARM/dma-mappіng: don't override ->dma_coherent when set from a bus notifier

Christoph Hellwig · Christoph Hellwig · commit 49bc8bebae79 · 2022-10-06T14:30:51.000+02:00
Commit ae626eb ("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: ae626eb ("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>
diff --git 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
