Commit 1c3b002c authored by Frank Li's avatar Frank Li Committed by Bjorn Helgaas
Browse files

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: default avatarFrank Li <Frank.Li@nxp.com>
[mani: minor code cleanups and reworded commit message]
Signed-off-by: default avatarManivannan Sadhasivam <mani@kernel.org>
[bhelgaas: fix kernel-doc]
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Tested-by: default avatarNiklas Cassel <cassel@kernel.org>
Link: https://patch.msgid.link/20250710-ep-msi-v21-3-57683fc7fb25@nxp.com
parent 19272b37

drivers/pci/endpoint/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -28,6 +28,14 @@ config PCI_ENDPOINT_CONFIGFS 
	   configure the endpoint function and used to bind the

	   function with an endpoint controller.



config PCI_ENDPOINT_MSI_DOORBELL

	bool "PCI Endpoint MSI Doorbell Support"

	depends on PCI_ENDPOINT && GENERIC_MSI_IRQ

	help

	  This enables the EP's MSI interrupt controller to function as a

	  doorbell. The RC can trigger doorbell in EP by writing data to a

	  dedicated BAR, which the EP maps to the controller's message address.



source "drivers/pci/endpoint/functions/Kconfig"



endmenu

drivers/pci/endpoint/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -6,3 +6,4 @@ 
obj-$(CONFIG_PCI_ENDPOINT_CONFIGFS)	+= pci-ep-cfs.o

obj-$(CONFIG_PCI_ENDPOINT)		+= pci-epc-core.o pci-epf-core.o\

					   pci-epc-mem.o functions/

obj-$(CONFIG_PCI_ENDPOINT_MSI_DOORBELL)	+= pci-ep-msi.o

drivers/pci/endpoint/pci-ep-msi.c

0 → 100644
+92 −0
Original line number Diff line number Diff line 
// 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;

	}



	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);

include/linux/pci-ep-msi.h

0 → 100644
+28 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

/*

 * PCI Endpoint *Function* side MSI header file

 *

 * Copyright (C) 2024 NXP

 * Author: Frank Li <Frank.Li@nxp.com>

 */



#ifndef __PCI_EP_MSI__

#define __PCI_EP_MSI__



struct pci_epf;



#ifdef CONFIG_PCI_ENDPOINT_MSI_DOORBELL

int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 nums);

void pci_epf_free_doorbell(struct pci_epf *epf);

#else

static inline int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 nums)

{

	return -ENODATA;

}



static inline void pci_epf_free_doorbell(struct pci_epf *epf)

{

}

#endif /* CONFIG_GENERIC_MSI_IRQ */



#endif /* __PCI_EP_MSI__ */

include/linux/pci-epf.h

+15 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/configfs.h>

#include <linux/device.h>

#include <linux/mod_devicetable.h>

#include <linux/msi.h>

#include <linux/pci.h>



struct pci_epf;
@@ -128,6 +129,16 @@ struct pci_epf_bar { 
	int		flags;

};



/**

 * struct pci_epf_doorbell_msg - represents doorbell message

 * @msg: MSI message

 * @virq: IRQ number of this doorbell MSI message

 */

struct pci_epf_doorbell_msg {

	struct msi_msg msg;

	int virq;

};



/**

 * struct pci_epf - represents the PCI EPF device

 * @dev: the PCI EPF device
@@ -155,6 +166,8 @@ struct pci_epf_bar { 
 * @vfunction_num_map: bitmap to manage virtual function number

 * @pci_vepf: list of virtual endpoint functions associated with this function

 * @event_ops: callbacks for capturing the EPC events

 * @db_msg: data for MSI from RC side

 * @num_db: number of doorbells

 */

struct pci_epf {

	struct device		dev;
@@ -185,6 +198,8 @@ struct pci_epf { 
	unsigned long		vfunction_num_map;

	struct list_head	pci_vepf;

	const struct pci_epc_event_ops *event_ops;

	struct pci_epf_doorbell_msg *db_msg;

	u16 num_db;

};



/**