232 lines
7.3 KiB
ReStructuredText
232 lines
7.3 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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:Author: Kishon Vijay Abraham I <kishon@ti.com>
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This document is a guide to use the PCI Endpoint Framework in order to create
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endpoint controller driver, endpoint function driver, and using configfs
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interface to bind the function driver to the controller driver.
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Introduction
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============
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Linux has a comprehensive PCI subsystem to support PCI controllers that
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operates in Root Complex mode. The subsystem has capability to scan PCI bus,
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assign memory resources and IRQ resources, load PCI driver (based on
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vendor ID, device ID), support other services like hot-plug, power management,
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advanced error reporting and virtual channels.
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However the PCI controller IP integrated in some SoCs is capable of operating
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either in Root Complex mode or Endpoint mode. PCI Endpoint Framework will
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add endpoint mode support in Linux. This will help to run Linux in an
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EP system which can have a wide variety of use cases from testing or
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validation, co-processor accelerator, etc.
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PCI Endpoint Core
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=================
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The PCI Endpoint Core layer comprises 3 components: the Endpoint Controller
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library, the Endpoint Function library, and the configfs layer to bind the
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endpoint function with the endpoint controller.
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PCI Endpoint Controller(EPC) Library
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------------------------------------
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The EPC library provides APIs to be used by the controller that can operate
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in endpoint mode. It also provides APIs to be used by function driver/library
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in order to implement a particular endpoint function.
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APIs for the PCI controller Driver
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This section lists the APIs that the PCI Endpoint core provides to be used
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by the PCI controller driver.
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* devm_pci_epc_create()/pci_epc_create()
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The PCI controller driver should implement the following ops:
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* write_header: ops to populate configuration space header
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* set_bar: ops to configure the BAR
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* clear_bar: ops to reset the BAR
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* alloc_addr_space: ops to allocate in PCI controller address space
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* free_addr_space: ops to free the allocated address space
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* raise_irq: ops to raise a legacy, MSI or MSI-X interrupt
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* start: ops to start the PCI link
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* stop: ops to stop the PCI link
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The PCI controller driver can then create a new EPC device by invoking
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devm_pci_epc_create()/pci_epc_create().
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* devm_pci_epc_destroy()/pci_epc_destroy()
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The PCI controller driver can destroy the EPC device created by either
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devm_pci_epc_create() or pci_epc_create() using devm_pci_epc_destroy() or
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pci_epc_destroy().
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* pci_epc_linkup()
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In order to notify all the function devices that the EPC device to which
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they are linked has established a link with the host, the PCI controller
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driver should invoke pci_epc_linkup().
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* pci_epc_mem_init()
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Initialize the pci_epc_mem structure used for allocating EPC addr space.
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* pci_epc_mem_exit()
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Cleanup the pci_epc_mem structure allocated during pci_epc_mem_init().
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EPC APIs for the PCI Endpoint Function Driver
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This section lists the APIs that the PCI Endpoint core provides to be used
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by the PCI endpoint function driver.
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* pci_epc_write_header()
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The PCI endpoint function driver should use pci_epc_write_header() to
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write the standard configuration header to the endpoint controller.
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* pci_epc_set_bar()
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The PCI endpoint function driver should use pci_epc_set_bar() to configure
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the Base Address Register in order for the host to assign PCI addr space.
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Register space of the function driver is usually configured
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using this API.
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* pci_epc_clear_bar()
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The PCI endpoint function driver should use pci_epc_clear_bar() to reset
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the BAR.
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* pci_epc_raise_irq()
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The PCI endpoint function driver should use pci_epc_raise_irq() to raise
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Legacy Interrupt, MSI or MSI-X Interrupt.
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* pci_epc_mem_alloc_addr()
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The PCI endpoint function driver should use pci_epc_mem_alloc_addr(), to
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allocate memory address from EPC addr space which is required to access
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RC's buffer
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* pci_epc_mem_free_addr()
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The PCI endpoint function driver should use pci_epc_mem_free_addr() to
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free the memory space allocated using pci_epc_mem_alloc_addr().
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Other EPC APIs
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~~~~~~~~~~~~~~
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There are other APIs provided by the EPC library. These are used for binding
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the EPF device with EPC device. pci-ep-cfs.c can be used as reference for
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using these APIs.
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* pci_epc_get()
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Get a reference to the PCI endpoint controller based on the device name of
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the controller.
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* pci_epc_put()
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Release the reference to the PCI endpoint controller obtained using
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pci_epc_get()
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* pci_epc_add_epf()
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Add a PCI endpoint function to a PCI endpoint controller. A PCIe device
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can have up to 8 functions according to the specification.
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* pci_epc_remove_epf()
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Remove the PCI endpoint function from PCI endpoint controller.
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* pci_epc_start()
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The PCI endpoint function driver should invoke pci_epc_start() once it
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has configured the endpoint function and wants to start the PCI link.
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* pci_epc_stop()
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The PCI endpoint function driver should invoke pci_epc_stop() to stop
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the PCI LINK.
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PCI Endpoint Function(EPF) Library
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----------------------------------
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The EPF library provides APIs to be used by the function driver and the EPC
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library to provide endpoint mode functionality.
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EPF APIs for the PCI Endpoint Function Driver
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This section lists the APIs that the PCI Endpoint core provides to be used
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by the PCI endpoint function driver.
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* pci_epf_register_driver()
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The PCI Endpoint Function driver should implement the following ops:
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* bind: ops to perform when a EPC device has been bound to EPF device
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* unbind: ops to perform when a binding has been lost between a EPC
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device and EPF device
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* linkup: ops to perform when the EPC device has established a
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connection with a host system
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The PCI Function driver can then register the PCI EPF driver by using
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pci_epf_register_driver().
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* pci_epf_unregister_driver()
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The PCI Function driver can unregister the PCI EPF driver by using
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pci_epf_unregister_driver().
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* pci_epf_alloc_space()
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The PCI Function driver can allocate space for a particular BAR using
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pci_epf_alloc_space().
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* pci_epf_free_space()
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The PCI Function driver can free the allocated space
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(using pci_epf_alloc_space) by invoking pci_epf_free_space().
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APIs for the PCI Endpoint Controller Library
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This section lists the APIs that the PCI Endpoint core provides to be used
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by the PCI endpoint controller library.
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* pci_epf_linkup()
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The PCI endpoint controller library invokes pci_epf_linkup() when the
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EPC device has established the connection to the host.
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Other EPF APIs
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~~~~~~~~~~~~~~
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There are other APIs provided by the EPF library. These are used to notify
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the function driver when the EPF device is bound to the EPC device.
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pci-ep-cfs.c can be used as reference for using these APIs.
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* pci_epf_create()
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Create a new PCI EPF device by passing the name of the PCI EPF device.
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This name will be used to bind the EPF device to a EPF driver.
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* pci_epf_destroy()
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Destroy the created PCI EPF device.
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* pci_epf_bind()
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pci_epf_bind() should be invoked when the EPF device has been bound to
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a EPC device.
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* pci_epf_unbind()
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pci_epf_unbind() should be invoked when the binding between EPC device
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and EPF device is lost.
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