From: Sunil Goutham sgoutham@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 sgoutham@cavium.com [will: rewrote commit message and cosmetic changes] Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin alexander.levin@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; } }