iommu/arm-smmu-v3: Use explicit mb() when moving cons pointer

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[ Upstream commit a868e85304 ]

After removing an entry from a queue (e.g. reading an event in
arm_smmu_evtq_thread()) it is necessary to advance the MMIO consumer
pointer to free the queue slot back to the SMMU. A memory barrier is
required here so that all reads targetting the queue entry have
completed before the consumer pointer is updated.

The implementation of queue_inc_cons() relies on a writel() to complete
the previous reads, but this is incorrect because writel() is only
guaranteed to complete prior writes. This patch replaces the call to
writel() with an mb(); writel_relaxed() sequence, which gives us the
read->write ordering which we require.

Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Will Deacon 2018-11-07 22:58:24 +00:00 • committed by Greg Kroah-Hartman

parent b34b2f334b

commit 2e6743c608

1 changed files with 7 additions and 1 deletions

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drivers/iommu/arm-smmu-v3.c

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