net: iosm: irq handling

1) Request interrupt vector, frees allocated resource.
2) Registers IRQ handler.
Signed-off-by: M Chetan Kumar <m.chetan.kumar@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wwan/iosm/iosm_ipc_irq.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020-21 Intel Corporation.
+ */
+
+#include "iosm_ipc_pcie.h"
+#include "iosm_ipc_protocol.h"
+
+static void ipc_write_dbell_reg(struct iosm_pcie *ipc_pcie, int irq_n, u32 data)
+{
+	void __iomem *write_reg;
+
+	/* Select the first doorbell register, which is only currently needed
+	 * by CP.
+	 */
+	write_reg = (void __iomem *)((u8 __iomem *)ipc_pcie->ipc_regs +
+				     ipc_pcie->doorbell_write +
+				     (irq_n * ipc_pcie->doorbell_reg_offset));
+
+	/* Fire the doorbell irq by writing data on the doorbell write pointer
+	 * register.
+	 */
+	iowrite32(data, write_reg);
+}
+
+void ipc_doorbell_fire(struct iosm_pcie *ipc_pcie, int irq_n, u32 data)
+{
+	ipc_write_dbell_reg(ipc_pcie, irq_n, data);
+}
+
+/* Threaded Interrupt handler for MSI interrupts */
+static irqreturn_t ipc_msi_interrupt(int irq, void *dev_id)
+{
+	struct iosm_pcie *ipc_pcie = dev_id;
+	int instance = irq - ipc_pcie->pci->irq;
+
+	/* Shift the MSI irq actions to the IPC tasklet. IRQ_NONE means the
+	 * irq was not from the IPC device or could not be served.
+	 */
+	if (instance >= ipc_pcie->nvec)
+		return IRQ_NONE;
+
+	if (!test_bit(0, &ipc_pcie->suspend))
+		ipc_imem_irq_process(ipc_pcie->imem, instance);
+
+	return IRQ_HANDLED;
+}
+
+void ipc_release_irq(struct iosm_pcie *ipc_pcie)
+{
+	struct pci_dev *pdev = ipc_pcie->pci;
+
+	if (pdev->msi_enabled) {
+		while (--ipc_pcie->nvec >= 0)
+			free_irq(pdev->irq + ipc_pcie->nvec, ipc_pcie);
+	}
+	pci_free_irq_vectors(pdev);
+}
+
+int ipc_acquire_irq(struct iosm_pcie *ipc_pcie)
+{
+	struct pci_dev *pdev = ipc_pcie->pci;
+	int i, rc = -EINVAL;
+
+	ipc_pcie->nvec = pci_alloc_irq_vectors(pdev, IPC_MSI_VECTORS,
+					       IPC_MSI_VECTORS, PCI_IRQ_MSI);
+
+	if (ipc_pcie->nvec < 0) {
+		rc = ipc_pcie->nvec;
+		goto error;
+	}
+
+	if (!pdev->msi_enabled)
+		goto error;
+
+	for (i = 0; i < ipc_pcie->nvec; ++i) {
+		rc = request_threaded_irq(pdev->irq + i, NULL,
+					  ipc_msi_interrupt, IRQF_ONESHOT,
+					  KBUILD_MODNAME, ipc_pcie);
+		if (rc) {
+			dev_err(ipc_pcie->dev, "unable to grab IRQ, rc=%d", rc);
+			ipc_pcie->nvec = i;
+			ipc_release_irq(ipc_pcie);
+			goto error;
+		}
+	}
+
+error:
+	return rc;
+}

drivers/net/wwan/iosm/iosm_ipc_irq.h

+/* SPDX-License-Identifier: GPL-2.0-only
+ *
+ * Copyright (C) 2020-21 Intel Corporation.
+ */
+
+#ifndef IOSM_IPC_IRQ_H
+#define IOSM_IPC_IRQ_H
+
+struct iosm_pcie;
+
+/**
+ * ipc_doorbell_fire - fire doorbell to CP
+ * @ipc_pcie:	Pointer to iosm_pcie
+ * @irq_n:	Doorbell type
+ * @data:	ipc state
+ */
+void ipc_doorbell_fire(struct iosm_pcie *ipc_pcie, int irq_n, u32 data);
+
+/**
+ * ipc_release_irq - Release the IRQ handler.
+ * @ipc_pcie:	Pointer to iosm_pcie struct
+ */
+void ipc_release_irq(struct iosm_pcie *ipc_pcie);
+
+/**
+ * ipc_acquire_irq - acquire IRQ & register IRQ handler.
+ * @ipc_pcie:	Pointer to iosm_pcie struct
+ *
+ * Return: 0 on success and failure value on error
+ */
+int ipc_acquire_irq(struct iosm_pcie *ipc_pcie);
+
+#endif