[PATCH v10 05/15] iommu/arm-smmu-v3: Add a helper to drain cmd queues
From: Pranjal Shrivastava <praan@google.com>
Date: 2026-09-08 17:17:27
Also in:
driver-core, linux-iommu
Subsystem:
arm smmu drivers, iommu subsystem, the rest · Maintainers:
Will Deacon, Joerg Roedel, Linus Torvalds
Before we suspend SMMU, we want to ensure that all commands (especially ATC_INV) have been flushed by the CMDQ, i.e. the CMDQs are empty. Add arm_smmu_drain_cmdqs() that drains the command queue using the arm_smmu_drain_queue() helper. Reviewed-by: Nicolin Chen <redacted> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Pranjal Shrivastava <praan@google.com> --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 27 +++++++++++++++++++++ 1 file changed, 27 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index d809b625f7fb..dc2fc02b5163 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c@@ -1028,6 +1028,33 @@ int arm_smmu_drain_queue(struct arm_smmu_device *smmu, return -ETIMEDOUT; } +/* + * Lockless, the caller must ensure that no concurrent command submissions + * can happen (such as during suspend where clients are already quiesced). + * Polling until PROD == CONS ensures all pending commands in the queue have + * been consumed by the hardware. + */ +static int __maybe_unused arm_smmu_drain_cmdqs(struct arm_smmu_device *smmu) +{ + int ret, err; + + /* + * We skip cmdq locking here since this helper is only called + * from contexts (like suspend) where the caller has already + * ensured that new command submissions are fully closed. + */ + ret = arm_smmu_drain_queue(smmu, &smmu->cmdq.q, true); + + /* Drain all implementation-specific queues */ + if (smmu->impl_ops && smmu->impl_ops->drain_queues) { + err = smmu->impl_ops->drain_queues(smmu); + if (err) + ret = err; + } + + return ret; +} + static void arm_smmu_page_response(struct device *dev, struct iopf_fault *unused, struct iommu_page_response *resp) {
--
2.55.0.979.g7e5102b832-goog