Date:   Wed, 18 Oct 2023 19:19:22 -0700
From:   Georgi Djakov <quic_c_gdjako@...cinc.com>
To:     <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <will@...nel.org>, <robin.murphy@....com>,
        <joro@...tes.org>
CC:     <devicetree@...r.kernel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <quic_cgoldswo@...cinc.com>,
        <quic_sukadev@...cinc.com>, <quic_pdaly@...cinc.com>,
        <quic_sudaraja@...cinc.com>, <djakov@...nel.org>
Subject: [PATCH 5/6] iommu/arm-smmu-qcom: Use a custom context fault handler for sdm845

The sdm845 platform now supports TBUs, so let's get additional debug
info from the TBUs when a context fault occurs. Implement a custom
context fault handler that does both software + hardware page table
walks and TLB Invalidate All.

Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 148 +++++++++++++++++++++
 1 file changed, 148 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index d20263a1cd2c..bcb1e2edec4e 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -60,6 +60,11 @@ struct qsmmuv500_tbu {
 
 static DEFINE_SPINLOCK(ecats_lock);
 
+static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
+{
+	return container_of(dom, struct arm_smmu_domain, domain);
+}
+
 static struct qsmmuv500_tbu *qsmmuv500_find_tbu(struct qcom_smmu *qsmmu, u32 sid)
 {
 	struct qsmmuv500_tbu *tbu = NULL;
@@ -326,6 +331,145 @@ static phys_addr_t qsmmuv500_iova_to_phys(struct arm_smmu_domain *smmu_domain,
 
 	return phys;
 }
+
+static phys_addr_t qcom_smmu_iova_to_phys_hard(struct iommu_domain *domain, dma_addr_t iova)
+{
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	int idx = smmu_domain->cfg.cbndx;
+	u32 frsynra;
+	u16 sid;
+
+	frsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(idx));
+	sid = FIELD_GET(ARM_SMMU_CBFRSYNRA_SID, frsynra);
+
+	return qsmmuv500_iova_to_phys(smmu_domain, iova, sid);
+}
+
+static phys_addr_t qcom_smmu_verify_fault(struct iommu_domain *domain, dma_addr_t iova, u32 fsr)
+{
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+	struct io_pgtable *iop = io_pgtable_ops_to_pgtable(smmu_domain->pgtbl_ops);
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	phys_addr_t phys_post_tlbiall;
+	phys_addr_t phys;
+
+	phys = qcom_smmu_iova_to_phys_hard(domain, iova);
+	io_pgtable_tlb_flush_all(iop);
+	phys_post_tlbiall = qcom_smmu_iova_to_phys_hard(domain, iova);
+
+	if (phys != phys_post_tlbiall) {
+		dev_err(smmu->dev,
+			"ATOS results differed across TLBIALL... (before: %pa after: %pa)\n",
+			&phys, &phys_post_tlbiall);
+	}
+
+	return (phys == 0 ? phys_post_tlbiall : phys);
+}
+
+static irqreturn_t qcom_smmu_context_fault(int irq, void *dev)
+{
+	struct iommu_domain *domain = dev;
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+	struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	u32 fsr, fsynr, cbfrsynra, resume = 0;
+	int idx = smmu_domain->cfg.cbndx;
+	phys_addr_t phys_soft;
+	unsigned long iova;
+	int ret, tmp;
+
+	static DEFINE_RATELIMIT_STATE(_rs,
+				      DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+
+	fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR);
+	if (!(fsr & ARM_SMMU_FSR_FAULT))
+		return IRQ_NONE;
+
+	fsynr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSYNR0);
+	iova = arm_smmu_cb_readq(smmu, idx, ARM_SMMU_CB_FAR);
+	cbfrsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(idx));
+
+	phys_soft = ops->iova_to_phys(ops, iova);
+
+	tmp = report_iommu_fault(domain, NULL, iova,
+				 fsynr & ARM_SMMU_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
+	if (!tmp || tmp == -EBUSY) {
+		dev_dbg(smmu->dev,
+			"Context fault handled by client: iova=0x%08lx, fsr=0x%x, fsynr=0x%x, cb=%d\n",
+			iova, fsr, fsynr, idx);
+		dev_dbg(smmu->dev, "soft iova-to-phys=%pa\n", &phys_soft);
+		ret = IRQ_HANDLED;
+		resume = ARM_SMMU_RESUME_TERMINATE;
+	} else {
+		phys_addr_t phys_atos = qcom_smmu_verify_fault(domain, iova, fsr);
+
+		if (__ratelimit(&_rs)) {
+			dev_err(smmu->dev,
+				"Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n",
+				fsr, iova, fsynr, cbfrsynra, idx);
+			dev_err(smmu->dev,
+				"FSR    = %08x [%s%s%s%s%s%s%s%s%s], SID=0x%x\n",
+				fsr,
+				(fsr & 0x02) ? "TF " : "",
+				(fsr & 0x04) ? "AFF " : "",
+				(fsr & 0x08) ? "PF " : "",
+				(fsr & 0x10) ? "EF " : "",
+				(fsr & 0x20) ? "TLBMCF " : "",
+				(fsr & 0x40) ? "TLBLKF " : "",
+				(fsr & 0x80) ? "MHF " : "",
+				(fsr & 0x40000000) ? "SS " : "",
+				(fsr & 0x80000000) ? "MULTI " : "",
+				cbfrsynra);
+
+			dev_err(smmu->dev,
+				"soft iova-to-phys=%pa\n", &phys_soft);
+			if (!phys_soft)
+				dev_err(smmu->dev,
+					"SOFTWARE TABLE WALK FAILED! Looks like %s accessed an unmapped address!\n",
+					dev_name(smmu->dev));
+			if (phys_atos)
+				dev_err(smmu->dev, "hard iova-to-phys (ATOS)=%pa\n",
+					&phys_atos);
+			else
+				dev_err(smmu->dev, "hard iova-to-phys (ATOS) failed\n");
+		}
+		ret = IRQ_NONE;
+		resume = ARM_SMMU_RESUME_TERMINATE;
+	}
+
+	/*
+	 * If the client returns -EBUSY, do not clear FSR and do not RESUME
+	 * if stalled. This is required to keep the IOMMU client stalled on
+	 * the outstanding fault. This gives the client a chance to take any
+	 * debug action and then terminate the stalled transaction.
+	 * So, the sequence in case of stall on fault should be:
+	 * 1) Do not clear FSR or write to RESUME here
+	 * 2) Client takes any debug action
+	 * 3) Client terminates the stalled transaction and resumes the IOMMU
+	 * 4) Client clears FSR. The FSR should only be cleared after 3) and
+	 *    not before so that the fault remains outstanding. This ensures
+	 *    SCTLR.HUPCF has the desired effect if subsequent transactions also
+	 *    need to be terminated.
+	 */
+	if (tmp != -EBUSY) {
+		/* Clear the faulting FSR */
+		arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
+
+		/*
+		 * Barrier required to ensure that the FSR is cleared
+		 * before resuming SMMU operation
+		 */
+		wmb();
+
+		/* Retry or terminate any stalled transactions */
+		if (fsr & ARM_SMMU_FSR_SS)
+			arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_RESUME, resume);
+	}
+
+	return ret;
+}
 #endif
 
 static void qcom_smmu_tlb_sync(struct arm_smmu_device *smmu, int page,
@@ -727,6 +871,10 @@ static const struct arm_smmu_impl sdm845_smmu_500_impl = {
 	.reset = qcom_sdm845_smmu500_reset,
 	.write_s2cr = qcom_smmu_write_s2cr,
 	.tlb_sync = qcom_smmu_tlb_sync,
+#ifdef CONFIG_ARM_SMMU_QCOM_TBU
+	.context_fault = qcom_smmu_context_fault,
+	.context_fault_needs_threaded_irq = true,
+#endif
 };
 
 static const struct arm_smmu_impl qcom_adreno_smmu_v2_impl = {

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