iommu/arm-smmu-qcom-debug: Add support for TBUs

Operating the TBUs (Translation Buffer Units) from Linux on Qualcomm
platforms can help with debugging context faults. To help with that,
the TBUs can run ATOS (Address Translation Operations) to manually
trigger address translation of IOVA to physical address in hardware
and provide more details when a context fault happens.

The driver will control the resources needed by the TBU to allow
running the debug operations such as ATOS, check for outstanding
transactions, do snapshot capture etc.

Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Link: https://lore.kernel.org/r/20240417133731.2055383-3-quic_c_gdjako@quicinc.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: Georgi Djakov

drivers/iommu/Kconfig

@@ -379,10 +379,14 @@ config ARM_SMMU_QCOM_DEBUG
 	depends on ARM_SMMU_QCOM
 	help
 	  Support for implementation specific debug features in ARM SMMU
-	  hardware found in QTI platforms.
-
-	  Say Y here to enable debug for issues such as TLB sync timeouts
-	  which requires implementation defined register dumps.
+	  hardware found in QTI platforms. This include support for
+	  the Translation Buffer Units (TBU) that can be used to obtain
+	  additional information when debugging memory management issues
+	  like context faults.
+
+	  Say Y here to enable debug for issues such as context faults
+	  or TLB sync timeouts which requires implementation defined
+	  register dumps.
 
 config ARM_SMMU_V3
 	tristate "ARM Ltd. System MMU Version 3 (SMMUv3) Support"

drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c

@@ -1,15 +1,66 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
+#include <linux/cleanup.h>
 #include <linux/device.h>
+#include <linux/interconnect.h>
 #include <linux/firmware/qcom/qcom_scm.h>
+#include <linux/iopoll.h>
+#include <linux/list.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
 #include <linux/ratelimit.h>
+#include <linux/spinlock.h>
 
 #include "arm-smmu.h"
 #include "arm-smmu-qcom.h"
 
+#define TBU_DBG_TIMEOUT_US		100
+#define DEBUG_AXUSER_REG		0x30
+#define DEBUG_AXUSER_CDMID		GENMASK_ULL(43, 36)
+#define DEBUG_AXUSER_CDMID_VAL		0xff
+#define DEBUG_PAR_REG			0x28
+#define DEBUG_PAR_FAULT_VAL		BIT(0)
+#define DEBUG_PAR_PA			GENMASK_ULL(47, 12)
+#define DEBUG_SID_HALT_REG		0x0
+#define DEBUG_SID_HALT_VAL		BIT(16)
+#define DEBUG_SID_HALT_SID		GENMASK(9, 0)
+#define DEBUG_SR_HALT_ACK_REG		0x20
+#define DEBUG_SR_HALT_ACK_VAL		BIT(1)
+#define DEBUG_SR_ECATS_RUNNING_VAL	BIT(0)
+#define DEBUG_TXN_AXCACHE		GENMASK(5, 2)
+#define DEBUG_TXN_AXPROT		GENMASK(8, 6)
+#define DEBUG_TXN_AXPROT_PRIV		0x1
+#define DEBUG_TXN_AXPROT_NSEC		0x2
+#define DEBUG_TXN_TRIGG_REG		0x18
+#define DEBUG_TXN_TRIGGER		BIT(0)
+#define DEBUG_VA_ADDR_REG		0x8
+
+static LIST_HEAD(tbu_list);
+static DEFINE_MUTEX(tbu_list_lock);
+static DEFINE_SPINLOCK(atos_lock);
+
+struct qcom_tbu {
+	struct device *dev;
+	struct device_node *smmu_np;
+	u32 sid_range[2];
+	struct list_head list;
+	struct clk *clk;
+	struct icc_path	*path;
+	void __iomem *base;
+	spinlock_t halt_lock; /* multiple halt or resume can't execute concurrently */
+	int halt_count;
+};
+
+static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
+{
+	return container_of(smmu, struct qcom_smmu, smmu);
+}
+
 void qcom_smmu_tlb_sync_debug(struct arm_smmu_device *smmu)
 {
 	int ret;
@@ -49,3 +100,305 @@ void qcom_smmu_tlb_sync_debug(struct arm_smmu_device *smmu)
 			tbu_pwr_status, sync_inv_ack, sync_inv_progress);
 	}
 }
+
+static struct qcom_tbu *qcom_find_tbu(struct qcom_smmu *qsmmu, u32 sid)
+{
+	struct qcom_tbu *tbu;
+	u32 start, end;
+
+	guard(mutex)(&tbu_list_lock);
+
+	if (list_empty(&tbu_list))
+		return NULL;
+
+	list_for_each_entry(tbu, &tbu_list, list) {
+		start = tbu->sid_range[0];
+		end = start + tbu->sid_range[1];
+
+		if (qsmmu->smmu.dev->of_node == tbu->smmu_np &&
+		    start <= sid && sid < end)
+			return tbu;
+	}
+	dev_err(qsmmu->smmu.dev, "Unable to find TBU for sid 0x%x\n", sid);
+
+	return NULL;
+}
+
+static int qcom_tbu_halt(struct qcom_tbu *tbu, struct arm_smmu_domain *smmu_domain)
+{
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	int ret = 0, idx = smmu_domain->cfg.cbndx;
+	u32 val, fsr, status;
+
+	guard(spinlock_irqsave)(&tbu->halt_lock);
+	if (tbu->halt_count) {
+		tbu->halt_count++;
+		return ret;
+	}
+
+	val = readl_relaxed(tbu->base + DEBUG_SID_HALT_REG);
+	val |= DEBUG_SID_HALT_VAL;
+	writel_relaxed(val, tbu->base + DEBUG_SID_HALT_REG);
+
+	fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR);
+	if ((fsr & ARM_SMMU_FSR_FAULT) && (fsr & ARM_SMMU_FSR_SS)) {
+		u32 sctlr_orig, sctlr;
+
+		/*
+		 * We are in a fault. Our request to halt the bus will not
+		 * complete until transactions in front of us (such as the fault
+		 * itself) have completed. Disable iommu faults and terminate
+		 * any existing transactions.
+		 */
+		sctlr_orig = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_SCTLR);
+		sctlr = sctlr_orig & ~(ARM_SMMU_SCTLR_CFCFG | ARM_SMMU_SCTLR_CFIE);
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, sctlr);
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_RESUME, ARM_SMMU_RESUME_TERMINATE);
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, sctlr_orig);
+	}
+
+	if (readl_poll_timeout_atomic(tbu->base + DEBUG_SR_HALT_ACK_REG, status,
+				      (status & DEBUG_SR_HALT_ACK_VAL),
+				      0, TBU_DBG_TIMEOUT_US)) {
+		dev_err(tbu->dev, "Timeout while trying to halt TBU!\n");
+		ret = -ETIMEDOUT;
+
+		val = readl_relaxed(tbu->base + DEBUG_SID_HALT_REG);
+		val &= ~DEBUG_SID_HALT_VAL;
+		writel_relaxed(val, tbu->base + DEBUG_SID_HALT_REG);
+
+		return ret;
+	}
+
+	tbu->halt_count = 1;
+
+	return ret;
+}
+
+static void qcom_tbu_resume(struct qcom_tbu *tbu)
+{
+	u32 val;
+
+	guard(spinlock_irqsave)(&tbu->halt_lock);
+	if (!tbu->halt_count) {
+		WARN(1, "%s: halt_count is 0", dev_name(tbu->dev));
+		return;
+	}
+
+	if (tbu->halt_count > 1) {
+		tbu->halt_count--;
+		return;
+	}
+
+	val = readl_relaxed(tbu->base + DEBUG_SID_HALT_REG);
+	val &= ~DEBUG_SID_HALT_VAL;
+	writel_relaxed(val, tbu->base + DEBUG_SID_HALT_REG);
+
+	tbu->halt_count = 0;
+}
+
+static phys_addr_t qcom_tbu_trigger_atos(struct arm_smmu_domain *smmu_domain,
+					 struct qcom_tbu *tbu, dma_addr_t iova, u32 sid)
+{
+	bool atos_timedout = false;
+	phys_addr_t phys = 0;
+	ktime_t timeout;
+	u64 val;
+
+	/* Set address and stream-id */
+	val = readq_relaxed(tbu->base + DEBUG_SID_HALT_REG);
+	val &= ~DEBUG_SID_HALT_SID;
+	val |= FIELD_PREP(DEBUG_SID_HALT_SID, sid);
+	writeq_relaxed(val, tbu->base + DEBUG_SID_HALT_REG);
+	writeq_relaxed(iova, tbu->base + DEBUG_VA_ADDR_REG);
+	val = FIELD_PREP(DEBUG_AXUSER_CDMID, DEBUG_AXUSER_CDMID_VAL);
+	writeq_relaxed(val, tbu->base + DEBUG_AXUSER_REG);
+
+	/* Write-back read and write-allocate */
+	val = FIELD_PREP(DEBUG_TXN_AXCACHE, 0xf);
+
+	/* Non-secure access */
+	val |= FIELD_PREP(DEBUG_TXN_AXPROT, DEBUG_TXN_AXPROT_NSEC);
+
+	/* Privileged access */
+	val |= FIELD_PREP(DEBUG_TXN_AXPROT, DEBUG_TXN_AXPROT_PRIV);
+
+	val |= DEBUG_TXN_TRIGGER;
+	writeq_relaxed(val, tbu->base + DEBUG_TXN_TRIGG_REG);
+
+	timeout = ktime_add_us(ktime_get(), TBU_DBG_TIMEOUT_US);
+	for (;;) {
+		val = readl_relaxed(tbu->base + DEBUG_SR_HALT_ACK_REG);
+		if (!(val & DEBUG_SR_ECATS_RUNNING_VAL))
+			break;
+		val = readl_relaxed(tbu->base + DEBUG_PAR_REG);
+		if (val & DEBUG_PAR_FAULT_VAL)
+			break;
+		if (ktime_compare(ktime_get(), timeout) > 0) {
+			atos_timedout = true;
+			break;
+		}
+	}
+
+	val = readq_relaxed(tbu->base + DEBUG_PAR_REG);
+	if (val & DEBUG_PAR_FAULT_VAL)
+		dev_err(tbu->dev, "ATOS generated a fault interrupt! PAR = %llx, SID=0x%x\n",
+			val, sid);
+	else if (atos_timedout)
+		dev_err_ratelimited(tbu->dev, "ATOS translation timed out!\n");
+	else
+		phys = FIELD_GET(DEBUG_PAR_PA, val);
+
+	/* Reset hardware */
+	writeq_relaxed(0, tbu->base + DEBUG_TXN_TRIGG_REG);
+	writeq_relaxed(0, tbu->base + DEBUG_VA_ADDR_REG);
+	val = readl_relaxed(tbu->base + DEBUG_SID_HALT_REG);
+	val &= ~DEBUG_SID_HALT_SID;
+	writel_relaxed(val, tbu->base + DEBUG_SID_HALT_REG);
+
+	return phys;
+}
+
+static phys_addr_t qcom_iova_to_phys(struct arm_smmu_domain *smmu_domain,
+				     dma_addr_t iova, u32 sid)
+{
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
+	int idx = smmu_domain->cfg.cbndx;
+	struct qcom_tbu *tbu;
+	u32 sctlr_orig, sctlr;
+	phys_addr_t phys = 0;
+	int attempt = 0;
+	int ret;
+	u64 fsr;
+
+	tbu = qcom_find_tbu(qsmmu, sid);
+	if (!tbu)
+		return 0;
+
+	ret = icc_set_bw(tbu->path, 0, UINT_MAX);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(tbu->clk);
+	if (ret)
+		goto disable_icc;
+
+	ret = qcom_tbu_halt(tbu, smmu_domain);
+	if (ret)
+		goto disable_clk;
+
+	/*
+	 * ATOS/ECATS can trigger the fault interrupt, so disable it temporarily
+	 * and check for an interrupt manually.
+	 */
+	sctlr_orig = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_SCTLR);
+	sctlr = sctlr_orig & ~(ARM_SMMU_SCTLR_CFCFG | ARM_SMMU_SCTLR_CFIE);
+	arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, sctlr);
+
+	fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR);
+	if (fsr & ARM_SMMU_FSR_FAULT) {
+		/* Clear pending interrupts */
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
+
+		/*
+		 * TBU halt takes care of resuming any stalled transcation.
+		 * Kept it here for completeness sake.
+		 */
+		if (fsr & ARM_SMMU_FSR_SS)
+			arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_RESUME,
+					  ARM_SMMU_RESUME_TERMINATE);
+	}
+
+	/* Only one concurrent atos operation */
+	scoped_guard(spinlock_irqsave, &atos_lock) {
+		/*
+		 * If the translation fails, attempt the lookup more time."
+		 */
+		do {
+			phys = qcom_tbu_trigger_atos(smmu_domain, tbu, iova, sid);
+
+			fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR);
+			if (fsr & ARM_SMMU_FSR_FAULT) {
+				/* Clear pending interrupts */
+				arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
+
+				if (fsr & ARM_SMMU_FSR_SS)
+					arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_RESUME,
+							  ARM_SMMU_RESUME_TERMINATE);
+			}
+		} while (!phys && attempt++ < 2);
+
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, sctlr_orig);
+	}
+	qcom_tbu_resume(tbu);
+
+	/* Read to complete prior write transcations */
+	readl_relaxed(tbu->base + DEBUG_SR_HALT_ACK_REG);
+
+disable_clk:
+	clk_disable_unprepare(tbu->clk);
+disable_icc:
+	icc_set_bw(tbu->path, 0, 0);
+
+	return phys;
+}
+
+static int qcom_tbu_probe(struct platform_device *pdev)
+{
+	struct of_phandle_args args = { .args_count = 2 };
+	struct device_node *np = pdev->dev.of_node;
+	struct device *dev = &pdev->dev;
+	struct qcom_tbu *tbu;
+
+	tbu = devm_kzalloc(dev, sizeof(*tbu), GFP_KERNEL);
+	if (!tbu)
+		return -ENOMEM;
+
+	tbu->dev = dev;
+	INIT_LIST_HEAD(&tbu->list);
+	spin_lock_init(&tbu->halt_lock);
+
+	if (of_parse_phandle_with_args(np, "qcom,stream-id-range", "#iommu-cells", 0, &args)) {
+		dev_err(dev, "Cannot parse the 'qcom,stream-id-range' DT property\n");
+		return -EINVAL;
+	}
+
+	tbu->smmu_np =  args.np;
+	tbu->sid_range[0] = args.args[0];
+	tbu->sid_range[1] = args.args[1];
+	of_node_put(args.np);
+
+	tbu->base = devm_of_iomap(dev, np, 0, NULL);
+	if (IS_ERR(tbu->base))
+		return PTR_ERR(tbu->base);
+
+	tbu->clk = devm_clk_get_optional(dev, NULL);
+	if (IS_ERR(tbu->clk))
+		return PTR_ERR(tbu->clk);
+
+	tbu->path = devm_of_icc_get(dev, NULL);
+	if (IS_ERR(tbu->path))
+		return PTR_ERR(tbu->path);
+
+	guard(mutex)(&tbu_list_lock);
+	list_add_tail(&tbu->list, &tbu_list);
+
+	return 0;
+}
+
+static const struct of_device_id qcom_tbu_of_match[] = {
+	{ .compatible = "qcom,sc7280-tbu" },
+	{ .compatible = "qcom,sdm845-tbu" },
+	{ }
+};
+
+static struct platform_driver qcom_tbu_driver = {
+	.driver = {
+		.name           = "qcom_tbu",
+		.of_match_table = qcom_tbu_of_match,
+	},
+	.probe = qcom_tbu_probe,
+};
+builtin_platform_driver(qcom_tbu_driver);