From: Rob Clark <robdclark@xxxxxxxxxxxx>
When games, browser, or anything using a lot of GPU buffers exits, there
can be many hundreds or thousands of buffers to unmap and free. If the
GPU is otherwise suspended, this can cause arm-smmu to resume/suspend
for each buffer, resulting 5-10 seconds worth of reprogramming the
context bank (arm_smmu_write_context_bank()/arm_smmu_write_s2cr()/etc).
To the user it would appear that the system just locked up.
A simple solution is to use pm_runtime_put_autosuspend() instead, so we
don't immediately suspend the SMMU device.
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
drivers/iommu/arm-smmu.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 7c503a6bc585..5abc0d210d90 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -122,7 +122,7 @@ static inline int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
static inline void arm_smmu_rpm_put(struct arm_smmu_device *smmu)
{
if (pm_runtime_enabled(smmu->dev))
- pm_runtime_put(smmu->dev);
+ pm_runtime_put_autosuspend(smmu->dev);
}
static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
@@ -1154,6 +1154,20 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
/* Looks ok, so add the device to the domain */
ret = arm_smmu_domain_add_master(smmu_domain, fwspec);
+ /*
+ * Setup an autosuspend delay to avoid bouncing runpm state.
+ * Otherwise, if a driver for a suspendend consumer device
+ * unmaps buffers, it will runpm resume/suspend for each one.
+ *
+ * For example, when used by a GPU device, when an application
+ * or game exits, it can trigger unmapping 100s or 1000s of
+ * buffers. With a runpm cycle for each buffer, that adds up
+ * to 5-10sec worth of reprogramming the context bank, while
+ * the system appears to be locked up to the user.
+ */
+ pm_runtime_set_autosuspend_delay(smmu->dev, 20);
+ pm_runtime_use_autosuspend(smmu->dev);
+
rpm_put:
arm_smmu_rpm_put(smmu);
return ret;
--
2.21.0
