iommu/arm-smmu: Avoid pathological RPM behaviour for unmaps (ee9bdfed) · Commits · 戴 / test

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. Reviewed-by:

Robin Murphy <robin.murphy@arm.com> Signed-off-by:

Rob Clark <robdclark@chromium.org> Signed-off-by:

Will Deacon <will@kernel.org>

drivers/iommu/arm-smmu.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -123,7 +123,7 @@ 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)
		@@ -1167,6 +1167,20 @@ 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 suspended 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;

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