1 files changed, 100 insertions, 0 deletions
diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
new file mode 100644
index 000000000000..9ca89cbfec15
--- /dev/null
+++ b/drivers/pci/endpoint/pci-ep-msi.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PCI Endpoint *Controller* (EPC) MSI library
+ *
+ * Copyright (C) 2025 NXP
+ * Author: Frank Li <Frank.Li@nxp.com>
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/msi.h>
+#include <linux/of_irq.h>
+#include <linux/pci-epc.h>
+#include <linux/pci-epf.h>
+#include <linux/pci-ep-cfs.h>
+#include <linux/pci-ep-msi.h>
+#include <linux/slab.h>
+
+static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
+{
+	struct pci_epc *epc;
+	struct pci_epf *epf;
+
+	epc = pci_epc_get(dev_name(msi_desc_to_dev(desc)));
+	if (!epc)
+		return;
+
+	epf = list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list);
+
+	if (epf && epf->db_msg && desc->msi_index < epf->num_db)
+		memcpy(&epf->db_msg[desc->msi_index].msg, msg, sizeof(*msg));
+
+	pci_epc_put(epc);
+}
+
+int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+{
+	struct pci_epc *epc = epf->epc;
+	struct device *dev = &epf->dev;
+	struct irq_domain *domain;
+	void *msg;
+	int ret;
+	int i;
+
+	/* TODO: Multi-EPF support */
+	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
+		dev_err(dev, "MSI doorbell doesn't support multiple EPF\n");
+		return -EINVAL;
+	}
+
+	domain = of_msi_map_get_device_domain(epc->dev.parent, 0,
+					      DOMAIN_BUS_PLATFORM_MSI);
+	if (!domain) {
+		dev_err(dev, "Can't find MSI domain for EPC\n");
+		return -ENODEV;
+	}
+
+	if (!irq_domain_is_msi_parent(domain))
+		return -ENODEV;
+
+	if (!irq_domain_is_msi_immutable(domain)) {
+		dev_err(dev, "Mutable MSI controller not supported\n");
+		return -ENODEV;
+	}
+
+	dev_set_msi_domain(epc->dev.parent, domain);
+
+	msg = kcalloc(num_db, sizeof(struct pci_epf_doorbell_msg), GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	epf->num_db = num_db;
+	epf->db_msg = msg;
+
+	ret = platform_device_msi_init_and_alloc_irqs(epc->dev.parent, num_db,
+						      pci_epf_write_msi_msg);
+	if (ret) {
+		dev_err(dev, "Failed to allocate MSI\n");
+		kfree(msg);
+		return ret;
+	}
+
+	for (i = 0; i < num_db; i++)
+		epf->db_msg[i].virq = msi_get_virq(epc->dev.parent, i);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
+
+void pci_epf_free_doorbell(struct pci_epf *epf)
+{
+	platform_device_msi_free_irqs_all(epf->epc->dev.parent);
+
+	kfree(epf->db_msg);
+	epf->db_msg = NULL;
+	epf->num_db = 0;
+}
+EXPORT_SYMBOL_GPL(pci_epf_free_doorbell);