Kishon Vijay Abraham I | a8a5be0 | 2017-03-27 15:14:58 +0530 | [diff] [blame] | 1 | PCI ENDPOINT FRAMEWORK |
| 2 | Kishon Vijay Abraham I <kishon@ti.com> |
| 3 | |
| 4 | This document is a guide to use the PCI Endpoint Framework in order to create |
| 5 | endpoint controller driver, endpoint function driver, and using configfs |
| 6 | interface to bind the function driver to the controller driver. |
| 7 | |
| 8 | 1. Introduction |
| 9 | |
| 10 | Linux has a comprehensive PCI subsystem to support PCI controllers that |
| 11 | operates in Root Complex mode. The subsystem has capability to scan PCI bus, |
| 12 | assign memory resources and IRQ resources, load PCI driver (based on |
| 13 | vendor ID, device ID), support other services like hot-plug, power management, |
| 14 | advanced error reporting and virtual channels. |
| 15 | |
| 16 | However the PCI controller IP integrated in some SoCs is capable of operating |
| 17 | either in Root Complex mode or Endpoint mode. PCI Endpoint Framework will |
| 18 | add endpoint mode support in Linux. This will help to run Linux in an |
| 19 | EP system which can have a wide variety of use cases from testing or |
| 20 | validation, co-processor accelerator, etc. |
| 21 | |
| 22 | 2. PCI Endpoint Core |
| 23 | |
| 24 | The PCI Endpoint Core layer comprises 3 components: the Endpoint Controller |
| 25 | library, the Endpoint Function library, and the configfs layer to bind the |
| 26 | endpoint function with the endpoint controller. |
| 27 | |
| 28 | 2.1 PCI Endpoint Controller(EPC) Library |
| 29 | |
| 30 | The EPC library provides APIs to be used by the controller that can operate |
| 31 | in endpoint mode. It also provides APIs to be used by function driver/library |
| 32 | in order to implement a particular endpoint function. |
| 33 | |
| 34 | 2.1.1 APIs for the PCI controller Driver |
| 35 | |
| 36 | This section lists the APIs that the PCI Endpoint core provides to be used |
| 37 | by the PCI controller driver. |
| 38 | |
| 39 | *) devm_pci_epc_create()/pci_epc_create() |
| 40 | |
| 41 | The PCI controller driver should implement the following ops: |
| 42 | * write_header: ops to populate configuration space header |
| 43 | * set_bar: ops to configure the BAR |
| 44 | * clear_bar: ops to reset the BAR |
| 45 | * alloc_addr_space: ops to allocate in PCI controller address space |
| 46 | * free_addr_space: ops to free the allocated address space |
| 47 | * raise_irq: ops to raise a legacy or MSI interrupt |
| 48 | * start: ops to start the PCI link |
| 49 | * stop: ops to stop the PCI link |
| 50 | |
| 51 | The PCI controller driver can then create a new EPC device by invoking |
| 52 | devm_pci_epc_create()/pci_epc_create(). |
| 53 | |
| 54 | *) devm_pci_epc_destroy()/pci_epc_destroy() |
| 55 | |
| 56 | The PCI controller driver can destroy the EPC device created by either |
| 57 | devm_pci_epc_create() or pci_epc_create() using devm_pci_epc_destroy() or |
| 58 | pci_epc_destroy(). |
| 59 | |
| 60 | *) pci_epc_linkup() |
| 61 | |
| 62 | In order to notify all the function devices that the EPC device to which |
| 63 | they are linked has established a link with the host, the PCI controller |
| 64 | driver should invoke pci_epc_linkup(). |
| 65 | |
| 66 | *) pci_epc_mem_init() |
| 67 | |
| 68 | Initialize the pci_epc_mem structure used for allocating EPC addr space. |
| 69 | |
| 70 | *) pci_epc_mem_exit() |
| 71 | |
| 72 | Cleanup the pci_epc_mem structure allocated during pci_epc_mem_init(). |
| 73 | |
| 74 | 2.1.2 APIs for the PCI Endpoint Function Driver |
| 75 | |
| 76 | This section lists the APIs that the PCI Endpoint core provides to be used |
| 77 | by the PCI endpoint function driver. |
| 78 | |
| 79 | *) pci_epc_write_header() |
| 80 | |
| 81 | The PCI endpoint function driver should use pci_epc_write_header() to |
| 82 | write the standard configuration header to the endpoint controller. |
| 83 | |
| 84 | *) pci_epc_set_bar() |
| 85 | |
| 86 | The PCI endpoint function driver should use pci_epc_set_bar() to configure |
| 87 | the Base Address Register in order for the host to assign PCI addr space. |
| 88 | Register space of the function driver is usually configured |
| 89 | using this API. |
| 90 | |
| 91 | *) pci_epc_clear_bar() |
| 92 | |
| 93 | The PCI endpoint function driver should use pci_epc_clear_bar() to reset |
| 94 | the BAR. |
| 95 | |
| 96 | *) pci_epc_raise_irq() |
| 97 | |
| 98 | The PCI endpoint function driver should use pci_epc_raise_irq() to raise |
| 99 | Legacy Interrupt or MSI Interrupt. |
| 100 | |
| 101 | *) pci_epc_mem_alloc_addr() |
| 102 | |
| 103 | The PCI endpoint function driver should use pci_epc_mem_alloc_addr(), to |
| 104 | allocate memory address from EPC addr space which is required to access |
| 105 | RC's buffer |
| 106 | |
| 107 | *) pci_epc_mem_free_addr() |
| 108 | |
| 109 | The PCI endpoint function driver should use pci_epc_mem_free_addr() to |
| 110 | free the memory space allocated using pci_epc_mem_alloc_addr(). |
| 111 | |
| 112 | 2.1.3 Other APIs |
| 113 | |
| 114 | There are other APIs provided by the EPC library. These are used for binding |
| 115 | the EPF device with EPC device. pci-ep-cfs.c can be used as reference for |
| 116 | using these APIs. |
| 117 | |
| 118 | *) pci_epc_get() |
| 119 | |
| 120 | Get a reference to the PCI endpoint controller based on the device name of |
| 121 | the controller. |
| 122 | |
| 123 | *) pci_epc_put() |
| 124 | |
| 125 | Release the reference to the PCI endpoint controller obtained using |
| 126 | pci_epc_get() |
| 127 | |
| 128 | *) pci_epc_add_epf() |
| 129 | |
| 130 | Add a PCI endpoint function to a PCI endpoint controller. A PCIe device |
| 131 | can have up to 8 functions according to the specification. |
| 132 | |
| 133 | *) pci_epc_remove_epf() |
| 134 | |
| 135 | Remove the PCI endpoint function from PCI endpoint controller. |
| 136 | |
| 137 | *) pci_epc_start() |
| 138 | |
| 139 | The PCI endpoint function driver should invoke pci_epc_start() once it |
| 140 | has configured the endpoint function and wants to start the PCI link. |
| 141 | |
| 142 | *) pci_epc_stop() |
| 143 | |
| 144 | The PCI endpoint function driver should invoke pci_epc_stop() to stop |
| 145 | the PCI LINK. |
| 146 | |
| 147 | 2.2 PCI Endpoint Function(EPF) Library |
| 148 | |
| 149 | The EPF library provides APIs to be used by the function driver and the EPC |
| 150 | library to provide endpoint mode functionality. |
| 151 | |
| 152 | 2.2.1 APIs for the PCI Endpoint Function Driver |
| 153 | |
| 154 | This section lists the APIs that the PCI Endpoint core provides to be used |
| 155 | by the PCI endpoint function driver. |
| 156 | |
| 157 | *) pci_epf_register_driver() |
| 158 | |
| 159 | The PCI Endpoint Function driver should implement the following ops: |
| 160 | * bind: ops to perform when a EPC device has been bound to EPF device |
| 161 | * unbind: ops to perform when a binding has been lost between a EPC |
| 162 | device and EPF device |
| 163 | * linkup: ops to perform when the EPC device has established a |
| 164 | connection with a host system |
| 165 | |
| 166 | The PCI Function driver can then register the PCI EPF driver by using |
| 167 | pci_epf_register_driver(). |
| 168 | |
| 169 | *) pci_epf_unregister_driver() |
| 170 | |
| 171 | The PCI Function driver can unregister the PCI EPF driver by using |
| 172 | pci_epf_unregister_driver(). |
| 173 | |
| 174 | *) pci_epf_alloc_space() |
| 175 | |
| 176 | The PCI Function driver can allocate space for a particular BAR using |
| 177 | pci_epf_alloc_space(). |
| 178 | |
| 179 | *) pci_epf_free_space() |
| 180 | |
| 181 | The PCI Function driver can free the allocated space |
| 182 | (using pci_epf_alloc_space) by invoking pci_epf_free_space(). |
| 183 | |
| 184 | 2.2.2 APIs for the PCI Endpoint Controller Library |
| 185 | This section lists the APIs that the PCI Endpoint core provides to be used |
| 186 | by the PCI endpoint controller library. |
| 187 | |
| 188 | *) pci_epf_linkup() |
| 189 | |
| 190 | The PCI endpoint controller library invokes pci_epf_linkup() when the |
| 191 | EPC device has established the connection to the host. |
| 192 | |
| 193 | 2.2.2 Other APIs |
| 194 | There are other APIs provided by the EPF library. These are used to notify |
| 195 | the function driver when the EPF device is bound to the EPC device. |
| 196 | pci-ep-cfs.c can be used as reference for using these APIs. |
| 197 | |
| 198 | *) pci_epf_create() |
| 199 | |
| 200 | Create a new PCI EPF device by passing the name of the PCI EPF device. |
| 201 | This name will be used to bind the the EPF device to a EPF driver. |
| 202 | |
| 203 | *) pci_epf_destroy() |
| 204 | |
| 205 | Destroy the created PCI EPF device. |
| 206 | |
| 207 | *) pci_epf_bind() |
| 208 | |
| 209 | pci_epf_bind() should be invoked when the EPF device has been bound to |
| 210 | a EPC device. |
| 211 | |
| 212 | *) pci_epf_unbind() |
| 213 | |
| 214 | pci_epf_unbind() should be invoked when the binding between EPC device |
| 215 | and EPF device is lost. |