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authorSunil Goutham <sgoutham@cavium.com>2017-05-05 16:47:46 +0530
committerWill Deacon <will.deacon@arm.com>2017-06-23 17:57:56 +0100
commitb847de4e5087fc8577c38a697d14fd2a5ce93352 (patch)
treebc37e0ec58a5e42cb4632308b23816730a5c726f /drivers/iommu
parent2ea659a9ef488125eb46da6eb571de5eae5c43f6 (diff)
downloadlinux-b847de4e5087fc8577c38a697d14fd2a5ce93352.tar.bz2
iommu/arm-smmu-v3: Increase CMDQ drain timeout value
Waiting for a CMD_SYNC to be processed involves waiting for the command queue to drain, which can take an awful lot longer than waiting for a single entry to become available. Consequently, the common timeout value of 100us has been observed to be too short on some platforms when a CMD_SYNC is issued into a queued full of TLBI commands. This patch resolves the issue by using a different (1s) timeout when waiting for the CMDQ to drain and using a simple back-off mechanism when polling the cons pointer in the absence of WFE support. Signed-off-by: Sunil Goutham <sgoutham@cavium.com> [will: rewrote commit message and cosmetic changes] Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'drivers/iommu')
-rw-r--r--drivers/iommu/arm-smmu-v3.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 380969aa60d5..6a06be7626db 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -408,6 +408,7 @@
/* High-level queue structures */
#define ARM_SMMU_POLL_TIMEOUT_US 100
+#define ARM_SMMU_CMDQ_DRAIN_TIMEOUT_US 1000000 /* 1s! */
#define MSI_IOVA_BASE 0x8000000
#define MSI_IOVA_LENGTH 0x100000
@@ -737,7 +738,13 @@ static void queue_inc_prod(struct arm_smmu_queue *q)
*/
static int queue_poll_cons(struct arm_smmu_queue *q, bool drain, bool wfe)
{
- ktime_t timeout = ktime_add_us(ktime_get(), ARM_SMMU_POLL_TIMEOUT_US);
+ ktime_t timeout;
+ unsigned int delay = 1;
+
+ /* Wait longer if it's queue drain */
+ timeout = ktime_add_us(ktime_get(), drain ?
+ ARM_SMMU_CMDQ_DRAIN_TIMEOUT_US :
+ ARM_SMMU_POLL_TIMEOUT_US);
while (queue_sync_cons(q), (drain ? !queue_empty(q) : queue_full(q))) {
if (ktime_compare(ktime_get(), timeout) > 0)
@@ -747,7 +754,8 @@ static int queue_poll_cons(struct arm_smmu_queue *q, bool drain, bool wfe)
wfe();
} else {
cpu_relax();
- udelay(1);
+ udelay(delay);
+ delay *= 2;
}
}