Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
PCI: endpoint: Add RC-to-EP doorbell support using platform MSI controller
Implement the doorbell feature by mapping the EP's MSI interrupt controller
message address to a dedicated BAR.
The EPF driver should pass the actual message data to be written to the
message address by the host through implementation-specific logic.
Signed-off-by: Frank Li <Frank.Li@nxp.com>
[mani: minor code cleanups and reworded commit message]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
[bhelgaas: fix kernel-doc]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Niklas Cassel <cassel@kernel.org>
Link: https://patch.msgid.link/20250710-ep-msi-v21-3-57683fc7fb25@nxp.com
authored by
Frank Li
and committed by
Bjorn Helgaas
1c3b002c
19272b37
+144
+8
drivers/pci/endpoint/Kconfig
+8
drivers/pci/endpoint/Kconfig
···
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configure the endpoint function and used to bind the
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function with an endpoint controller.
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config PCI_ENDPOINT_MSI_DOORBELL
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bool "PCI Endpoint MSI Doorbell Support"
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depends on PCI_ENDPOINT && GENERIC_MSI_IRQ
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help
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This enables the EP's MSI interrupt controller to function as a
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doorbell. The RC can trigger doorbell in EP by writing data to a
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dedicated BAR, which the EP maps to the controller's message address.
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source "drivers/pci/endpoint/functions/Kconfig"
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endmenu
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drivers/pci/endpoint/Makefile
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drivers/pci/endpoint/Makefile
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drivers/pci/endpoint/pci-ep-msi.c
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drivers/pci/endpoint/pci-ep-msi.c
···
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// SPDX-License-Identifier: GPL-2.0
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/*
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* PCI Endpoint *Controller* (EPC) MSI library
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*
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* Copyright (C) 2025 NXP
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* Author: Frank Li <Frank.Li@nxp.com>
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*/
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#include <linux/device.h>
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#include <linux/export.h>
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#include <linux/irqdomain.h>
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#include <linux/module.h>
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#include <linux/msi.h>
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#include <linux/of_irq.h>
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#include <linux/pci-epc.h>
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#include <linux/pci-epf.h>
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#include <linux/pci-ep-cfs.h>
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#include <linux/pci-ep-msi.h>
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#include <linux/slab.h>
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static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
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{
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struct pci_epc *epc;
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struct pci_epf *epf;
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epc = pci_epc_get(dev_name(msi_desc_to_dev(desc)));
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if (!epc)
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return;
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epf = list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list);
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if (epf && epf->db_msg && desc->msi_index < epf->num_db)
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memcpy(&epf->db_msg[desc->msi_index].msg, msg, sizeof(*msg));
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pci_epc_put(epc);
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}
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int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
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{
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struct pci_epc *epc = epf->epc;
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struct device *dev = &epf->dev;
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struct irq_domain *domain;
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void *msg;
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int ret;
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int i;
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/* TODO: Multi-EPF support */
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if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
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dev_err(dev, "MSI doorbell doesn't support multiple EPF\n");
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return -EINVAL;
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}
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domain = of_msi_map_get_device_domain(epc->dev.parent, 0,
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DOMAIN_BUS_PLATFORM_MSI);
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if (!domain) {
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dev_err(dev, "Can't find MSI domain for EPC\n");
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return -ENODEV;
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}
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dev_set_msi_domain(epc->dev.parent, domain);
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msg = kcalloc(num_db, sizeof(struct pci_epf_doorbell_msg), GFP_KERNEL);
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if (!msg)
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return -ENOMEM;
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epf->num_db = num_db;
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epf->db_msg = msg;
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ret = platform_device_msi_init_and_alloc_irqs(epc->dev.parent, num_db,
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pci_epf_write_msi_msg);
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if (ret) {
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dev_err(dev, "Failed to allocate MSI\n");
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kfree(msg);
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return ret;
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}
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for (i = 0; i < num_db; i++)
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epf->db_msg[i].virq = msi_get_virq(epc->dev.parent, i);
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return ret;
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}
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EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
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void pci_epf_free_doorbell(struct pci_epf *epf)
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{
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platform_device_msi_free_irqs_all(epf->epc->dev.parent);
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kfree(epf->db_msg);
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epf->db_msg = NULL;
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epf->num_db = 0;
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}
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EXPORT_SYMBOL_GPL(pci_epf_free_doorbell);
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include/linux/pci-ep-msi.h
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include/linux/pci-ep-msi.h
···
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* PCI Endpoint *Function* side MSI header file
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*
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* Copyright (C) 2024 NXP
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* Author: Frank Li <Frank.Li@nxp.com>
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*/
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#ifndef __PCI_EP_MSI__
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#define __PCI_EP_MSI__
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struct pci_epf;
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#ifdef CONFIG_PCI_ENDPOINT_MSI_DOORBELL
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int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 nums);
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void pci_epf_free_doorbell(struct pci_epf *epf);
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#else
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static inline int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 nums)
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{
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return -ENODATA;
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}
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static inline void pci_epf_free_doorbell(struct pci_epf *epf)
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{
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}
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#endif /* CONFIG_GENERIC_MSI_IRQ */
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#endif /* __PCI_EP_MSI__ */
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include/linux/pci-epf.h
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include/linux/pci-epf.h
···
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#include <linux/configfs.h>
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#include <linux/device.h>
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#include <linux/mod_devicetable.h>
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#include <linux/msi.h>
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#include <linux/pci.h>
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struct pci_epf;
···
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};
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/**
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* struct pci_epf_doorbell_msg - represents doorbell message
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* @msg: MSI message
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* @virq: IRQ number of this doorbell MSI message
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*/
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struct pci_epf_doorbell_msg {
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struct msi_msg msg;
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int virq;
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};
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/**
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* struct pci_epf - represents the PCI EPF device
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* @dev: the PCI EPF device
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* @name: the name of the PCI EPF device
···
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* @vfunction_num_map: bitmap to manage virtual function number
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* @pci_vepf: list of virtual endpoint functions associated with this function
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* @event_ops: callbacks for capturing the EPC events
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* @db_msg: data for MSI from RC side
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* @num_db: number of doorbells
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*/
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struct pci_epf {
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struct device dev;
···
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unsigned long vfunction_num_map;
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struct list_head pci_vepf;
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const struct pci_epc_event_ops *event_ops;
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struct pci_epf_doorbell_msg *db_msg;
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u16 num_db;
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};
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/**