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231 lines
7.3 KiB
231 lines
7.3 KiB
.. SPDX-License-Identifier: GPL-2.0 |
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:Author: Kishon Vijay Abraham I <[email protected]> |
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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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