Date:   Fri, 27 Mar 2020 15:24:34 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     Andrew Murray <amurray@...goodpenguin.co.uk>,
        <linux-omap@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: [PATCH v4] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling

Due an issue with PCIe wrapper around DWC PCIe IP on dra7xx, driver
needs to ensure that there are no pending MSI IRQ vector set (i.e
PCIE_MSI_INTR0_STATUS reads 0 at least once) before exiting IRQ handler.
Else, the dra7xx PCIe wrapper will not register new MSI IRQs even though
PCIE_MSI_INTR0_STATUS shows IRQs are pending.

Therefore its no longer possible to use default IRQ handler provided by
DWC library. So, add irqchip implementation inside pci-dra7xx.c and
install new MSI IRQ handler to handle above errata.

This fixes a bug, where PCIe wifi cards with 4 DMA queues like Intel
8260 used to throw following error and stall during ping/iperf3 tests.

[   97.776310] iwlwifi 0000:01:00.0: Queue 9 stuck for 2500 ms.

Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
Acked-by: Kishon Vijay Abraham I <kishon@...com>
Tested-by: Kishon Vijay Abraham I <kishon@...com>
---

v4:
Simplify dra7xx_pcie_handle_msi_irq() by spliting inner loop into
separte function as suggested by Lorenzo

v3:
- Move loop to service all MSI IRQs into dra7xx_pcie_handle_msi_irq()
- Add a warning msg when loop counter overflows


 drivers/pci/controller/dwc/pci-dra7xx.c | 231 ++++++++++++++++++++----
 1 file changed, 195 insertions(+), 36 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-dra7xx.c b/drivers/pci/controller/dwc/pci-dra7xx.c
index 9bf7fa99b103..3b0e58f2de58 100644
--- a/drivers/pci/controller/dwc/pci-dra7xx.c
+++ b/drivers/pci/controller/dwc/pci-dra7xx.c
@@ -215,10 +215,6 @@ static int dra7xx_pcie_host_init(struct pcie_port *pp)
 	return 0;
 }
 
-static const struct dw_pcie_host_ops dra7xx_pcie_host_ops = {
-	.host_init = dra7xx_pcie_host_init,
-};
-
 static int dra7xx_pcie_intx_map(struct irq_domain *domain, unsigned int irq,
 				irq_hw_number_t hwirq)
 {
@@ -233,43 +229,77 @@ static const struct irq_domain_ops intx_domain_ops = {
 	.xlate = pci_irqd_intx_xlate,
 };
 
-static int dra7xx_pcie_init_irq_domain(struct pcie_port *pp)
+static int dra7xx_pcie_handle_msi(struct pcie_port *pp, int index)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
-	struct device *dev = pci->dev;
-	struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci);
-	struct device_node *node = dev->of_node;
-	struct device_node *pcie_intc_node =  of_get_next_child(node, NULL);
+	unsigned long val;
+	int pos, irq;
 
-	if (!pcie_intc_node) {
-		dev_err(dev, "No PCIe Intc node found\n");
-		return -ENODEV;
-	}
+	val = dw_pcie_readl_dbi(pci, PCIE_MSI_INTR0_STATUS +
+				   (index * MSI_REG_CTRL_BLOCK_SIZE));
+	if (!val)
+		return 0;
 
-	dra7xx->irq_domain = irq_domain_add_linear(pcie_intc_node, PCI_NUM_INTX,
-						   &intx_domain_ops, pp);
-	of_node_put(pcie_intc_node);
-	if (!dra7xx->irq_domain) {
-		dev_err(dev, "Failed to get a INTx IRQ domain\n");
-		return -ENODEV;
+	pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL, 0);
+	while (pos != MAX_MSI_IRQS_PER_CTRL) {
+		irq = irq_find_mapping(pp->irq_domain,
+				       (index * MAX_MSI_IRQS_PER_CTRL) + pos);
+		generic_handle_irq(irq);
+		pos++;
+		pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL, pos);
 	}
 
-	return 0;
+	return 1;
 }
 
-static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
+static void dra7xx_pcie_handle_msi_irq(struct pcie_port *pp)
 {
-	struct dra7xx_pcie *dra7xx = arg;
-	struct dw_pcie *pci = dra7xx->pci;
-	struct pcie_port *pp = &pci->pp;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	int ret, i, count, num_ctrls;
+
+	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
+
+	/**
+	 * Need to make sure all MSI status bits read 0 before exiting.
+	 * Else, new MSI IRQs are not registered by the wrapper. Have an
+	 * upperbound for the loop and exit the IRQ in case of IRQ flood
+	 * to avoid locking up system in interrupt context.
+	 */
+	count = 0;
+	do {
+		ret = 0;
+
+		for (i = 0; i < num_ctrls; i++)
+			ret |= dra7xx_pcie_handle_msi(pp, i);
+		count++;
+	} while (ret && count <= 1000);
+
+	if (count > 1000)
+		dev_warn_ratelimited(pci->dev,
+				     "Too many MSI IRQs to handle\n");
+}
+
+static void dra7xx_pcie_msi_irq_handler(struct irq_desc *desc)
+{
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	struct dra7xx_pcie *dra7xx;
+	struct dw_pcie *pci;
+	struct pcie_port *pp;
 	unsigned long reg;
 	u32 virq, bit;
 
+	chained_irq_enter(chip, desc);
+
+	pp = irq_desc_get_handler_data(desc);
+	pci = to_dw_pcie_from_pp(pp);
+	dra7xx = to_dra7xx_pcie(pci);
+
 	reg = dra7xx_pcie_readl(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI);
+	dra7xx_pcie_writel(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI, reg);
 
 	switch (reg) {
 	case MSI:
-		dw_handle_msi_irq(pp);
+		dra7xx_pcie_handle_msi_irq(pp);
 		break;
 	case INTA:
 	case INTB:
@@ -283,9 +313,7 @@ static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
 		break;
 	}
 
-	dra7xx_pcie_writel(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI, reg);
-
-	return IRQ_HANDLED;
+	chained_irq_exit(chip, desc);
 }
 
 static irqreturn_t dra7xx_pcie_irq_handler(int irq, void *arg)
@@ -347,6 +375,145 @@ static irqreturn_t dra7xx_pcie_irq_handler(int irq, void *arg)
 	return IRQ_HANDLED;
 }
 
+static int dra7xx_pcie_init_irq_domain(struct pcie_port *pp)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct device *dev = pci->dev;
+	struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci);
+	struct device_node *node = dev->of_node;
+	struct device_node *pcie_intc_node =  of_get_next_child(node, NULL);
+
+	if (!pcie_intc_node) {
+		dev_err(dev, "No PCIe Intc node found\n");
+		return -ENODEV;
+	}
+
+	irq_set_chained_handler_and_data(pp->irq, dra7xx_pcie_msi_irq_handler,
+					 pp);
+	dra7xx->irq_domain = irq_domain_add_linear(pcie_intc_node, PCI_NUM_INTX,
+						   &intx_domain_ops, pp);
+	of_node_put(pcie_intc_node);
+	if (!dra7xx->irq_domain) {
+		dev_err(dev, "Failed to get a INTx IRQ domain\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static void dra7xx_pcie_setup_msi_msg(struct irq_data *d, struct msi_msg *msg)
+{
+	struct pcie_port *pp = irq_data_get_irq_chip_data(d);
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	u64 msi_target;
+
+	msi_target = (u64)pp->msi_data;
+
+	msg->address_lo = lower_32_bits(msi_target);
+	msg->address_hi = upper_32_bits(msi_target);
+
+	msg->data = d->hwirq;
+
+	dev_dbg(pci->dev, "msi#%d address_hi %#x address_lo %#x\n",
+		(int)d->hwirq, msg->address_hi, msg->address_lo);
+}
+
+static int dra7xx_pcie_msi_set_affinity(struct irq_data *d,
+					const struct cpumask *mask,
+					bool force)
+{
+	return -EINVAL;
+}
+
+static void dra7xx_pcie_bottom_mask(struct irq_data *d)
+{
+	struct pcie_port *pp = irq_data_get_irq_chip_data(d);
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	unsigned int res, bit, ctrl;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&pp->lock, flags);
+
+	ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
+	res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
+	bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
+
+	pp->irq_mask[ctrl] |= BIT(bit);
+	dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_MASK + res,
+			   pp->irq_mask[ctrl]);
+
+	raw_spin_unlock_irqrestore(&pp->lock, flags);
+}
+
+static void dra7xx_pcie_bottom_unmask(struct irq_data *d)
+{
+	struct pcie_port *pp = irq_data_get_irq_chip_data(d);
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	unsigned int res, bit, ctrl;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&pp->lock, flags);
+
+	ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
+	res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
+	bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
+
+	pp->irq_mask[ctrl] &= ~BIT(bit);
+	dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_MASK + res,
+			   pp->irq_mask[ctrl]);
+
+	raw_spin_unlock_irqrestore(&pp->lock, flags);
+}
+
+static void dra7xx_pcie_bottom_ack(struct irq_data *d)
+{
+	struct pcie_port *pp  = irq_data_get_irq_chip_data(d);
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	unsigned int res, bit, ctrl;
+
+	ctrl = d->hwirq / MAX_MSI_IRQS_PER_CTRL;
+	res = ctrl * MSI_REG_CTRL_BLOCK_SIZE;
+	bit = d->hwirq % MAX_MSI_IRQS_PER_CTRL;
+
+	dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_STATUS + res, BIT(bit));
+}
+
+static struct irq_chip dra7xx_pci_msi_bottom_irq_chip = {
+	.name = "DRA7XX-PCI-MSI",
+	.irq_ack = dra7xx_pcie_bottom_ack,
+	.irq_compose_msi_msg = dra7xx_pcie_setup_msi_msg,
+	.irq_set_affinity = dra7xx_pcie_msi_set_affinity,
+	.irq_mask = dra7xx_pcie_bottom_mask,
+	.irq_unmask = dra7xx_pcie_bottom_unmask,
+};
+
+static int dra7xx_pcie_msi_host_init(struct pcie_port *pp)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	u32 ctrl, num_ctrls;
+
+	pp->msi_irq_chip = &dra7xx_pci_msi_bottom_irq_chip;
+
+	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
+	/* Initialize IRQ Status array */
+	for (ctrl = 0; ctrl < num_ctrls; ctrl++) {
+		pp->irq_mask[ctrl] = ~0;
+		dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_MASK +
+				    (ctrl * MSI_REG_CTRL_BLOCK_SIZE),
+				    pp->irq_mask[ctrl]);
+		dw_pcie_writel_dbi(pci, PCIE_MSI_INTR0_ENABLE +
+				    (ctrl * MSI_REG_CTRL_BLOCK_SIZE),
+				    ~0);
+	}
+
+	return dw_pcie_allocate_domains(pp);
+}
+
+static const struct dw_pcie_host_ops dra7xx_pcie_host_ops = {
+	.host_init = dra7xx_pcie_host_init,
+	.msi_host_init = dra7xx_pcie_msi_host_init,
+};
+
 static void dra7xx_pcie_ep_init(struct dw_pcie_ep *ep)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
@@ -467,14 +634,6 @@ static int __init dra7xx_add_pcie_port(struct dra7xx_pcie *dra7xx,
 		return pp->irq;
 	}
 
-	ret = devm_request_irq(dev, pp->irq, dra7xx_pcie_msi_irq_handler,
-			       IRQF_SHARED | IRQF_NO_THREAD,
-			       "dra7-pcie-msi",	dra7xx);
-	if (ret) {
-		dev_err(dev, "failed to request irq\n");
-		return ret;
-	}
-
 	ret = dra7xx_pcie_init_irq_domain(pp);
 	if (ret < 0)
 		return ret;
-- 
2.26.0

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