From: Sunil Goutham <sgout...@cavium.com>
[ Upstream commit b847de4e5087fc8577c38a697d14fd2a5ce93352 ]
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 <sgout...@cavium.com>
[will: rewrote commit message and cosmetic changes]
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
drivers/iommu/arm-smmu-v3.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 7f294f785ce6..399b7f31fccb 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -409,6 +409,7 @@
/* High-level queue structures */
#define ARM_SMMU_POLL_TIMEOUT_US 100
+#define ARM_SMMU_CMDQ_DRAIN_TIMEOUT_US 1000000 /* 1s! */
static bool disable_bypass;
module_param_named(disable_bypass, disable_bypass, bool, S_IRUGO);
@@ -726,7 +727,13 @@ 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)
@@ -736,7 +743,8 @@ static int queue_poll_cons(struct arm_smmu_queue *q, bool
drain, bool wfe)
wfe();
} else {
cpu_relax();
- udelay(1);
+ udelay(delay);
+ delay *= 2;
}
}
--
2.15.1
