From: Sunil Goutham <sgoutham@cavium.com>
Date: Fri, 5 May 2017 16:47:46 +0530
Subject: iommu/arm-smmu-v3: Increase CMDQ drain timeout value
Git-commit: b847de4e5087fc8577c38a697d14fd2a5ce93352
Patch-mainline: v4.13-rc1
References: bsc#1035479
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>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.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 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;
}
}
--
2.11.0