[PATCH v1 for-next] spi: spi-pci1xxxx: Fix Probe failure with Dual SPI instance with INTx interrupts

[Thangaraj Samynathan <thangaraj.s@microchip.com>]

Fixes a probe failure that occurs when dual SPI controllers are
enabled and INTx interrupts are used. Reduces the minimum required
number of interrupt vectors to 1 and registers a shared ISR when
the allocated vectors are fewer than the number of controllers.
This change ensures that the probe succeeds even with limited
vectors, restoring INTx functionality when multiple SPI
controllers are present.

Signed-off-by: Thangaraj Samynathan <thangaraj.s@microchip.com>
---
 drivers/spi/spi-pci1xxxx.c | 48 +++++++++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 14 deletions(-)

diff --git a/drivers/spi/spi-pci1xxxx.c b/drivers/spi/spi-pci1xxxx.c
index e9153570e9e9..9a7b86a5ec75 100644
--- a/drivers/spi/spi-pci1xxxx.c
+++ b/drivers/spi/spi-pci1xxxx.c
@@ -688,6 +688,17 @@ static irqreturn_t pci1xxxx_spi_isr(int irq, void *dev)
 		return pci1xxxx_spi_isr_io(irq, dev);
 }
 
+static irqreturn_t pci1xxxx_spi_shared_isr(int irq, void *dev)
+{
+	struct pci1xxxx_spi *par = dev;
+	u8 i = 0;
+
+	for (i = 0; i < par->total_hw_instances; i++)
+		pci1xxxx_spi_isr(irq, par->spi_int[i]);
+
+	return IRQ_HANDLED;
+}
+
 static bool pci1xxxx_spi_can_dma(struct spi_controller *host,
 				 struct spi_device *spi,
 				 struct spi_transfer *xfer)
@@ -705,6 +716,7 @@ static int pci1xxxx_spi_probe(struct pci_dev *pdev, const struct pci_device_id *
 	struct device *dev = &pdev->dev;
 	struct pci1xxxx_spi *spi_bus;
 	struct spi_controller *spi_host;
+	int num_vector = 0;
 	u32 regval;
 	int ret;
 
@@ -752,9 +764,9 @@ static int pci1xxxx_spi_probe(struct pci_dev *pdev, const struct pci_device_id *
 			if (!spi_bus->reg_base)
 				return -EINVAL;
 
-			ret = pci_alloc_irq_vectors(pdev, hw_inst_cnt, hw_inst_cnt,
-						    PCI_IRQ_ALL_TYPES);
-			if (ret < 0) {
+			num_vector = pci_alloc_irq_vectors(pdev, 1, hw_inst_cnt,
+							   PCI_IRQ_ALL_TYPES);
+			if (num_vector < 0) {
 				dev_err(&pdev->dev, "Error allocating MSI vectors\n");
 				return ret;
 			}
@@ -768,9 +780,15 @@ static int pci1xxxx_spi_probe(struct pci_dev *pdev, const struct pci_device_id *
 			       SPI_MST_EVENT_MASK_REG_OFFSET(spi_sub_ptr->hw_inst));
 			spi_sub_ptr->irq = pci_irq_vector(pdev, 0);
 
-			ret = devm_request_irq(&pdev->dev, spi_sub_ptr->irq,
-					       pci1xxxx_spi_isr, PCI1XXXX_IRQ_FLAGS,
-					       pci_name(pdev), spi_sub_ptr);
+			if (num_vector >= hw_inst_cnt)
+				ret = devm_request_irq(&pdev->dev, spi_sub_ptr->irq,
+						       pci1xxxx_spi_isr, PCI1XXXX_IRQ_FLAGS,
+						       pci_name(pdev), spi_sub_ptr);
+			else
+				ret = devm_request_irq(&pdev->dev, spi_sub_ptr->irq,
+						       pci1xxxx_spi_shared_isr,
+						       PCI1XXXX_IRQ_FLAGS | IRQF_SHARED,
+						       pci_name(pdev), spi_bus);
 			if (ret < 0) {
 				dev_err(&pdev->dev, "Unable to request irq : %d",
 					spi_sub_ptr->irq);
@@ -801,14 +819,16 @@ static int pci1xxxx_spi_probe(struct pci_dev *pdev, const struct pci_device_id *
 			regval &= ~SPI_INTR;
 			writel(regval, spi_bus->reg_base +
 			       SPI_MST_EVENT_MASK_REG_OFFSET(spi_sub_ptr->hw_inst));
-			spi_sub_ptr->irq = pci_irq_vector(pdev, iter);
-			ret = devm_request_irq(&pdev->dev, spi_sub_ptr->irq,
-					       pci1xxxx_spi_isr, PCI1XXXX_IRQ_FLAGS,
-					       pci_name(pdev), spi_sub_ptr);
-			if (ret < 0) {
-				dev_err(&pdev->dev, "Unable to request irq : %d",
-					spi_sub_ptr->irq);
-				return -ENODEV;
+			if (num_vector >= hw_inst_cnt) {
+				spi_sub_ptr->irq = pci_irq_vector(pdev, iter);
+				ret = devm_request_irq(&pdev->dev, spi_sub_ptr->irq,
+						       pci1xxxx_spi_isr, PCI1XXXX_IRQ_FLAGS,
+						       pci_name(pdev), spi_sub_ptr);
+				if (ret < 0) {
+					dev_err(&pdev->dev, "Unable to request irq : %d",
+						spi_sub_ptr->irq);
+					return -ENODEV;
+				}
 			}
 		}
 
-- 
2.25.1