Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b847de4e authored by Sunil Goutham's avatar Sunil Goutham Committed by Will Deacon
Browse files

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: default avatarSunil Goutham <sgoutham@cavium.com>
[will: rewrote commit message and cosmetic changes]
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 2ea659a9

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;

		}

	}