[PATCH v8 11/12] iommu/arm-smmu-v3: Invoke pm_runtime before hw access

[Pranjal Shrivastava <praan@google.com>]

Invoke the pm_runtime helpers at all places before accessing the hw.
The idea is to invoke runtime_pm helpers at common points which are used
by exposed ops or interrupt handlers. TLB and CFG invalidations are
elided if the SMMU is suspended by observing the CMDQ_PROD_STOP_FLAG.

Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     |  10 +-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 101 ++++++++++++++++--
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |   5 +-
 3 files changed, 108 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
index 1e9f7d2de344..2d729034e3bb 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
@@ -15,6 +15,11 @@ void *arm_smmu_hw_info(struct device *dev, u32 *length,
 	struct iommu_hw_info_arm_smmuv3 *info;
 	u32 __iomem *base_idr;
 	unsigned int i;
+	int ret;
+
+	ret = arm_smmu_rpm_get(master->smmu);
+	if (ret < 0)
+		return ERR_PTR(-EIO);
 
 	if (*type != IOMMU_HW_INFO_TYPE_DEFAULT &&
 	    *type != IOMMU_HW_INFO_TYPE_ARM_SMMUV3) {
@@ -24,8 +29,10 @@ void *arm_smmu_hw_info(struct device *dev, u32 *length,
 	}
 
 	info = kzalloc_obj(*info);
-	if (!info)
+	if (!info) {
+		arm_smmu_rpm_put(master->smmu);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	base_idr = master->smmu->base + ARM_SMMU_IDR0;
 	for (i = 0; i <= 5; i++)
@@ -36,6 +43,7 @@ void *arm_smmu_hw_info(struct device *dev, u32 *length,
 	*length = sizeof(*info);
 	*type = IOMMU_HW_INFO_TYPE_ARM_SMMUV3;
 
+	arm_smmu_rpm_put(master->smmu);
 	return info;
 }
 
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 24a1bcc8974f..2e260f85b8fd 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -112,7 +112,7 @@ static int arm_smmu_alloc_cd_tables(struct arm_smmu_master *master);
 static bool arm_smmu_ats_supported(struct arm_smmu_master *master);
 
 /* Runtime PM helpers */
-__maybe_unused static int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
+int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
 {
 	int ret;
 
@@ -128,7 +128,7 @@ __maybe_unused static int arm_smmu_rpm_get(struct arm_smmu_device *smmu)
 	return 0;
 }
 
-__maybe_unused static void arm_smmu_rpm_put(struct arm_smmu_device *smmu)
+void arm_smmu_rpm_put(struct arm_smmu_device *smmu)
 {
 	int ret;
 
@@ -983,7 +983,9 @@ static void arm_smmu_page_response(struct device *dev, struct iopf_fault *unused
 				   struct iommu_page_response *resp)
 {
 	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+	struct arm_smmu_device *smmu = master->smmu;
 	u8 resume_resp;
+	int ret;
 
 	if (WARN_ON(!master->stall_enabled))
 		return;
@@ -1001,6 +1003,25 @@ static void arm_smmu_page_response(struct device *dev, struct iopf_fault *unused
 		break;
 	}
 
+	/*
+	 * The SMMU is guaranteed to be active via device_link if any master is
+	 * active. Furthermore, on suspend we set GBPA to abort, flushing any
+	 * pending stalled transactions.
+	 *
+	 * Receiving a page fault while suspended implies a bug in the power
+	 * dependency chain or a stale event. Since the SMMU is powered down
+	 * and the command queue is inaccessible, we cannot issue the
+	 * RESUME command and must drop it.
+	 */
+	if (arm_smmu_cmdq_can_elide(smmu)) {
+		dev_err(smmu->dev, "Ignoring page fault while suspended\n");
+		return;
+	}
+
+	ret = arm_smmu_rpm_get(smmu);
+	if (ret < 0)
+		return;
+
 	arm_smmu_cmdq_issue_cmd(master->smmu,
 				arm_smmu_make_cmd_resume(master->streams[0].id,
 							 resp->grpid,
@@ -1011,6 +1032,7 @@ static void arm_smmu_page_response(struct device *dev, struct iopf_fault *unused
 	 * terminated... at some point in the future. PRI_RESP is fire and
 	 * forget.
 	 */
+	arm_smmu_rpm_put(smmu);
 }
 
 /* Invalidation array manipulation functions */
@@ -1536,7 +1558,6 @@ static void arm_smmu_sync_cd(struct arm_smmu_master *master,
 			smmu, &cmds,
 			arm_smmu_make_cmd_cfgi_cd(master->streams[i].id, ssid,
 						  leaf));
-
 	arm_smmu_cmdq_batch_submit(smmu, &cmds);
 }
 
@@ -1828,9 +1849,9 @@ static void arm_smmu_ste_writer_sync_entry(struct arm_smmu_entry_writer *writer)
 {
 	struct arm_smmu_ste_writer *ste_writer =
 		container_of(writer, struct arm_smmu_ste_writer, writer);
+	struct arm_smmu_device *smmu = writer->master->smmu;
 
-	arm_smmu_cmdq_issue_cmd_with_sync(
-		writer->master->smmu,
+	arm_smmu_cmdq_issue_cmd_with_sync(smmu,
 		arm_smmu_make_cmd_cfgi_ste(ste_writer->sid, true));
 }
 
@@ -2230,6 +2251,7 @@ static void arm_smmu_dump_event(struct arm_smmu_device *smmu, u64 *raw,
 
 static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 {
+	int ret;
 	u64 evt[EVTQ_ENT_DWORDS];
 	struct arm_smmu_event event = {0};
 	struct arm_smmu_device *smmu = dev;
@@ -2238,6 +2260,10 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
 				      DEFAULT_RATELIMIT_BURST);
 
+	ret = arm_smmu_rpm_get(smmu);
+	if (ret < 0)
+		return IRQ_NONE;
+
 	do {
 		while (!queue_remove_raw(q, evt)) {
 			arm_smmu_decode_event(smmu, evt, &event);
@@ -2258,6 +2284,7 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 
 	/* Sync our overflow flag, as we believe we're up to speed */
 	queue_sync_cons_ovf(q);
+	arm_smmu_rpm_put(smmu);
 	return IRQ_HANDLED;
 }
 
@@ -2295,6 +2322,11 @@ static irqreturn_t arm_smmu_priq_thread(int irq, void *dev)
 	struct arm_smmu_queue *q = &smmu->priq.q;
 	struct arm_smmu_ll_queue *llq = &q->llq;
 	u64 evt[PRIQ_ENT_DWORDS];
+	int ret;
+
+	ret = arm_smmu_rpm_get(smmu);
+	if (ret < 0)
+		return IRQ_NONE;
 
 	do {
 		while (!queue_remove_raw(q, evt))
@@ -2306,6 +2338,7 @@ static irqreturn_t arm_smmu_priq_thread(int irq, void *dev)
 
 	/* Sync our overflow flag, as we believe we're up to speed */
 	queue_sync_cons_ovf(q);
+	arm_smmu_rpm_put(smmu);
 	return IRQ_HANDLED;
 }
 
@@ -2361,8 +2394,33 @@ static irqreturn_t arm_smmu_handle_gerror(struct arm_smmu_device *smmu)
 static irqreturn_t arm_smmu_gerror_handler(int irq, void *dev)
 {
 	struct arm_smmu_device *smmu = dev;
+	irqreturn_t ret;
+
+	/*
+	 * Global Errors are only processed if the SMMU is active.
+	 *
+	 * If the STOP_FLAG is set (can_elide == true), the hardware is
+	 * either already disabled or in the process of being disabled.
+	 * Any errors captured during the quiesce/drain phase will be
+	 * handled by the explicit arm_smmu_handle_gerror() call at the
+	 * end of arm_smmu_runtime_suspend() callback. On resume, the
+	 * STOP_FLAG is cleared before interrupts are re-enabled, ensuring
+	 * no valid errors are missed.
+	 *
+	 * A lockless check is favoured here over a dynamic PM core check
+	 * since the runtime_pm_get_if_active would return false during
+	 * transient states like RPM_RESUMING & ignore level-triggered
+	 * interrupts.
+	 */
+	if (arm_smmu_cmdq_can_elide(smmu)) {
+		dev_err(smmu->dev,
+			"Ignoring gerror interrupt because the SMMU is suspended\n");
+		return IRQ_NONE;
+	}
+
+	ret = arm_smmu_handle_gerror(smmu);
 
-	return arm_smmu_handle_gerror(smmu);
+	return ret;
 }
 
 static irqreturn_t arm_smmu_combined_irq_thread(int irq, void *dev)
@@ -2445,6 +2503,10 @@ static int arm_smmu_atc_inv_master(struct arm_smmu_master *master,
 	struct arm_smmu_cmd cmd;
 	struct arm_smmu_cmdq_batch cmds;
 
+	/* Shouldn't hit the WARN if there's no devlink inconsistency */
+	if (WARN_ON_ONCE(arm_smmu_cmdq_can_elide(master->smmu)))
+		return 0;
+
 	cmd = arm_smmu_make_cmd_atc_inv_all(0, IOMMU_NO_PASID);
 	arm_smmu_cmdq_batch_init_cmd(master->smmu, &cmds, &cmd);
 	for (i = 0; i < master->num_streams; i++)
@@ -2690,7 +2752,16 @@ static void __arm_smmu_domain_inv_range(struct arm_smmu_invs *invs,
 
 		if (cmds.num &&
 		    (next == end || arm_smmu_invs_end_batch(cur, next))) {
+
+			/*
+			 * Concurrent suspend races are benign: the cmdq allocation cmpxchg
+			 * loop acts as the serialization point to safely drop the batch
+			 * without MMIO accesses. Concurrent resume is caught by the HW
+			 * reset cache invalidation, ensuring state consistency.
+			 */
 			arm_smmu_cmdq_batch_submit(smmu, &cmds);
+
+			/* Drop this batch to ensure the next one's fresh */
 			cmds.num = 0;
 		}
 		cur = next;
@@ -2703,6 +2774,9 @@ void arm_smmu_domain_inv_range(struct arm_smmu_domain *smmu_domain,
 {
 	struct arm_smmu_invs *invs;
 
+	if (arm_smmu_cmdq_can_elide(smmu_domain->smmu))
+		return;
+
 	/*
 	 * An invalidation request must follow some IOPTE change and then load
 	 * an invalidation array. In the meantime, a domain attachment mutates
@@ -5631,10 +5705,19 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 static void arm_smmu_device_remove(struct platform_device *pdev)
 {
 	struct arm_smmu_device *smmu = platform_get_drvdata(pdev);
+	int ret;
 
 	iommu_device_unregister(&smmu->iommu);
 	iommu_device_sysfs_remove(&smmu->iommu);
+
+	ret = arm_smmu_rpm_get(smmu);
+	if (ret <  0)
+		goto free_iopf;
+
 	arm_smmu_device_disable(smmu);
+	arm_smmu_rpm_put(smmu);
+
+free_iopf:
 	iopf_queue_free(smmu->evtq.iopf);
 	ida_destroy(&smmu->vmid_map);
 }
@@ -5642,8 +5725,14 @@ static void arm_smmu_device_remove(struct platform_device *pdev)
 static void arm_smmu_device_shutdown(struct platform_device *pdev)
 {
 	struct arm_smmu_device *smmu = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = arm_smmu_rpm_get(smmu);
+	if (ret < 0)
+		return;
 
 	arm_smmu_device_disable(smmu);
+	arm_smmu_rpm_put(smmu);
 }
 
 static int __maybe_unused arm_smmu_runtime_suspend(struct device *dev)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 51a3281a1e46..0bd5ad2670e0 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -1230,11 +1230,14 @@ int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
  * If we lose the race, that loop observes Q_STOP == 1 and safely
  * drops the command. If we win, the suspend thread waits for us.
  */
-static inline bool arm_smmu_can_elide(struct arm_smmu_device *smmu)
+static inline bool arm_smmu_cmdq_can_elide(struct arm_smmu_device *smmu)
 {
 	return !!Q_STOP(READ_ONCE(smmu->cmdq.q.llq.prod));
 }
 
+int arm_smmu_rpm_get(struct arm_smmu_device *smmu);
+void arm_smmu_rpm_put(struct arm_smmu_device *smmu);
+
 #ifdef CONFIG_ARM_SMMU_V3_SVA
 bool arm_smmu_sva_supported(struct arm_smmu_device *smmu);
 void arm_smmu_sva_notifier_synchronize(void);
-- 
2.54.0.1013.g208068f2d8-goog