iommu/arm-smmu-v3: Increase CMDQ drain timeout value (b847de4e) · Commits · 戴 / test

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>

drivers/iommu/arm-smmu-v3.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}
		}

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