From: Christoph Hellwig <hch@lst.de>
To: Russell King <linux@armlinux.org.uk>
Cc: "Robin Murphy" <robin.murphy@arm.com>,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
"Marek Behún" <kabel@kernel.org>
Subject: [PATCH 1/2] ARM/dma-mappіng: don't override ->dma_coherent when set from a bus notifier
Date: Thu, 6 Oct 2022 09:48:23 +0200 [thread overview]
Message-ID: <20221006074824.521457-2-hch@lst.de> (raw)
In-Reply-To: <20221006074824.521457-1-hch@lst.de>
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>
Tested-by: Marek Behún <kabel@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 089c9c644cce2..bfc7476f14114 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
--
2.30.2
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next prev parent reply other threads:[~2022-10-06 7:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-06 7:48 mvebu DMA fix Christoph Hellwig
2022-10-06 7:48 ` Christoph Hellwig [this message]
2022-10-06 7:48 ` [PATCH 2/2] ARM/dma-mapping: remove the dma_coherent member of struct dev_archdata Christoph Hellwig
2022-10-06 11:52 ` mvebu DMA fix Russell King (Oracle)
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