[PATCH] PCI: dwc: pci-dra7xx: Fix MSI IRQ handling

[Vignesh Raghavendra]

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@xxxxxx>
---
Based on discussions here: https://www.spinics.net/lists/linux-pci/msg70462.html

 drivers/pci/controller/dwc/pci-dra7xx.c | 227 ++++++++++++++++++++----
 1 file changed, 189 insertions(+), 38 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-dra7xx.c b/drivers/pci/controller/dwc/pci-dra7xx.c
index 9bf7fa99b103..07f242539ce9 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 +229,69 @@ 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_irq(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;
-	}
-
-	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;
+	int i, pos, irq;
+	unsigned long val;
+	u32 status, num_ctrls;
+	int ret = 0;
+
+	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
+
+	for (i = 0; i < num_ctrls; i++) {
+		status = dw_pcie_readl_dbi(pci, PCIE_MSI_INTR0_STATUS +
+					   (i * MSI_REG_CTRL_BLOCK_SIZE));
+		if (!status)
+			continue;
+
+		ret = 1;
+		val = status;
+		pos = 0;
+		while ((pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL,
+					    pos)) != MAX_MSI_IRQS_PER_CTRL) {
+			irq = irq_find_mapping(pp->irq_domain,
+					       (i * MAX_MSI_IRQS_PER_CTRL) +
+					       pos);
+			generic_handle_irq(irq);
+			pos++;
+		}
 	}
 
-	return 0;
+	return ret;
 }
 
-static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
+static void dra7xx_pcie_msi_irq_handler(struct irq_desc *desc)
 {
-	struct dra7xx_pcie *dra7xx = arg;
-	struct dw_pcie *pci = dra7xx->pci;
-	struct pcie_port *pp = &pci->pp;
+	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;
+	int count = 0;
+
+	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);
+		/**
+		 * 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.
+		 */
+		while (dra7xx_pcie_handle_msi_irq(pp) && count < 1000)
+			count++;
+
 		break;
 	case INTA:
 	case INTB:
@@ -283,9 +305,7 @@ 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 +367,145 @@ 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 +626,6 @@ 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;
-- 
2.25.0