diff options
| author | Will Deacon <will.deacon@arm.com> | 2018-11-07 22:58:24 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-02-12 19:44:54 +0100 |
| commit | d1069fc14266851c1e5eae4a33a5da864387c093 (patch) | |
| tree | 030c25fab31482bd7361c3cc85675ab6ef6bd3aa /drivers/iommu | |
| parent | 98e089c8b7b4b851d231826d7c814b20a969cde3 (diff) | |
iommu/arm-smmu-v3: Use explicit mb() when moving cons pointer
[ Upstream commit a868e8530441286342f90c1fd9c5f24de3aa2880 ]
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>
Diffstat (limited to 'drivers/iommu')
| -rw-r--r-- | drivers/iommu/arm-smmu-v3.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index ff4be1174ff0..7bd98585d78d 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -697,7 +697,13 @@ static void queue_inc_cons(struct arm_smmu_queue *q) u32 cons = (Q_WRP(q, q->cons) | Q_IDX(q, q->cons)) + 1; q->cons = Q_OVF(q, q->cons) | Q_WRP(q, cons) | Q_IDX(q, cons); - writel(q->cons, q->cons_reg); + + /* + * Ensure that all CPU accesses (reads and writes) to the queue + * are complete before we update the cons pointer. + */ + mb(); + writel_relaxed(q->cons, q->cons_reg); } static int queue_sync_prod(struct arm_smmu_queue *q) |