[PATCH AUTOSEL for 4.9 135/293] iommu/arm-smmu-v3: Increase CMDQ drain timeout value

[Sasha Levin]

From: Sunil Goutham 

[ 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 
[will: rewrote commit message and cosmetic changes]
Signed-off-by: Will Deacon 
Signed-off-by: Sasha Levin 
---
 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 100 /* 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;
}
}
 
-- 
2.15.1

[PATCH AUTOSEL for 4.9 135/293] iommu/arm-smmu-v3: Increase CMDQ drain timeout value

[Sasha Levin]

From: Sunil Goutham 

[ 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 
[will: rewrote commit message and cosmetic changes]
Signed-off-by: Will Deacon 
Signed-off-by: Sasha Levin 
---
 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 100 /* 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;
}
}
 
-- 
2.15.1