[PATCH v12 6/8] PCI: dwc: Implement special ISR handler for split MSI IRQ setup

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

If the PCIe DWC controller uses split MSI IRQs for reporting MSI
vectors, it is possible to detect, which group triggered the interrupt.
Provide an optimized version of MSI ISR handler that will handle just a
single MSI group instead of handling all of them.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
 .../pci/controller/dwc/pcie-designware-host.c | 86 ++++++++++++++-----
 1 file changed, 65 insertions(+), 21 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 98a57249ecaf..2b2de517301a 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -52,34 +52,42 @@ static struct msi_domain_info dw_pcie_msi_domain_info = {
 	.chip	= &dw_pcie_msi_irq_chip,
 };
 
+static inline irqreturn_t dw_handle_single_msi_group(struct pcie_port *pp, int i)
+{
+	int pos;
+	unsigned long val;
+	u32 status;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+
+	status = dw_pcie_readl_dbi(pci, PCIE_MSI_INTR0_STATUS +
+				   (i * MSI_REG_CTRL_BLOCK_SIZE));
+	if (!status)
+		return IRQ_NONE;
+
+	val = status;
+	pos = 0;
+	while ((pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL,
+				    pos)) != MAX_MSI_IRQS_PER_CTRL) {
+		generic_handle_domain_irq(pp->irq_domain,
+					  (i * MAX_MSI_IRQS_PER_CTRL) +
+					  pos);
+		pos++;
+	}
+
+	return IRQ_HANDLED;
+}
+
 /* MSI int handler */
 irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
 {
-	int i, pos;
-	unsigned long val;
-	u32 status, num_ctrls;
+	int i;
+	u32 num_ctrls;
 	irqreturn_t ret = IRQ_NONE;
-	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 
 	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 = IRQ_HANDLED;
-		val = status;
-		pos = 0;
-		while ((pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL,
-					    pos)) != MAX_MSI_IRQS_PER_CTRL) {
-			generic_handle_domain_irq(pp->irq_domain,
-						  (i * MAX_MSI_IRQS_PER_CTRL) +
-						  pos);
-			pos++;
-		}
-	}
+	for (i = 0; i < num_ctrls; i++)
+		ret |= dw_handle_single_msi_group(pp, i);
 
 	return ret;
 }
@@ -98,6 +106,38 @@ static void dw_chained_msi_isr(struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
+static void dw_split_msi_isr(struct irq_desc *desc)
+{
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	int irq = irq_desc_get_irq(desc);
+	struct pcie_port *pp;
+	int i;
+	u32 num_ctrls;
+	struct dw_pcie *pci;
+
+	chained_irq_enter(chip, desc);
+
+	pp = irq_desc_get_handler_data(desc);
+	pci = to_dw_pcie_from_pp(pp);
+
+	/*
+	 * Unlike generic dw_handle_msi_irq(), we can determine which group of
+	 * MSIs triggered the IRQ, so process just that group.
+	 */
+	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
+
+	for (i = 0; i < num_ctrls; i++) {
+		if (pp->msi_irq[i] == irq) {
+			dw_handle_single_msi_group(pp, i);
+			break;
+		}
+	}
+
+	WARN_ON_ONCE(i == num_ctrls);
+
+	chained_irq_exit(chip, desc);
+}
+
 static void dw_pci_setup_msi_msg(struct irq_data *d, struct msi_msg *msg)
 {
 	struct pcie_port *pp = irq_data_get_irq_chip_data(d);
@@ -336,6 +376,7 @@ static int dw_pcie_msi_host_init(struct pcie_port *pp)
 	struct platform_device *pdev = to_platform_device(dev);
 	int ret;
 	u32 ctrl, num_ctrls;
+	bool has_split_msi_irq = false;
 
 	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++)
 		pp->irq_mask[ctrl] = ~0;
@@ -344,6 +385,8 @@ static int dw_pcie_msi_host_init(struct pcie_port *pp)
 		ret = dw_pcie_parse_split_msi_irq(pp);
 		if (ret < 0 && ret != -ENXIO)
 			return ret;
+		else if (!ret)
+			has_split_msi_irq = true;
 	}
 
 	if (!pp->num_vectors)
@@ -372,6 +415,7 @@ static int dw_pcie_msi_host_init(struct pcie_port *pp)
 	for (ctrl = 0; ctrl < num_ctrls; ctrl++)
 		if (pp->msi_irq[ctrl] > 0)
 			irq_set_chained_handler_and_data(pp->msi_irq[ctrl],
+							 has_split_msi_irq ? dw_split_msi_isr :
 							 dw_chained_msi_isr,
 							 pp);
 
-- 
2.35.1