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