From b847de4e5087fc8577c38a697d14fd2a5ce93352 Mon Sep 17 00:00:00 2001 From: Sunil Goutham Date: Fri, 5 May 2017 16:47:46 +0530 Subject: [PATCH] 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 [will: rewrote commit message and cosmetic changes] Signed-off-by: Will Deacon --- 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; } }