[PATCH v5 02/24] Documentation: PCI: Guide to use PCI Endpoint Core Layer

Kishon Vijay Abraham I
2017-03-27T09:44:58Z

Add Documentation to help users use endpoint library to enable endpoint
mode in the PCI controller and add new PCI endpoint functions.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
---
Documentation/PCI/00-INDEX | 2 +
Documentation/PCI/endpoint/pci-endpoint.txt | 215 ++++++++++++++++++++++++++++
2 files changed, 217 insertions(+)
create mode 100644 Documentation/PCI/endpoint/pci-endpoint.txt

diff --git a/Documentation/PCI/00-INDEX b/Documentation/PCI/00-INDEX
index 147231f1613e..ba950b296bd8 100644
--- a/Documentation/PCI/00-INDEX
+++ b/Documentation/PCI/00-INDEX
@@ -12,3 +12,5 @@ pci.txt
- info on the PCI subsystem for device driver authors
pcieaer-howto.txt
- the PCI Express Advanced Error Reporting Driver Guide HOWTO
+endpoint/pci-endpoint.txt
+ - guide to add endpoint controller driver and endpoint function driver.
diff --git a/Documentation/PCI/endpoint/pci-endpoint.txt b/Documentation/PCI/endpoint/pci-endpoint.txt
new file mode 100644
index 000000000000..4a3e4388b37b
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-endpoint.txt
@@ -0,0 +1,215 @@
+ PCI ENDPOINT FRAMEWORK
+ 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.
+
+1. 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
+vendorid, deviceid), support other services like hot-plug, power management,
+advanced error reporting and virtual channels.
+
+However PCI controller IPs integrated in certain SoC 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..
+
+2. PCI Endpoint Core
+
+The PCI Endpoint Core layer comprises of 3 components: the Endpoint Controller
+library, the Endpoint Function library and the configfs layer to bind the
+endpoint function with the endpoint controller.
+
+2.1 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.
+
+2.1.1 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 or MSI 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().
+
+2.1.2 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 or MSI 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().
+
+2.1.3 Other 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 upto 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.
+
+2.2 PCI Endpoint Function(EPF) Library
+
+The EPF library provides APIs to be used by the function driver and the EPC
+library in order to provide endpoint mode functionality.
+
+2.2.1 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
+ * linkup: ops to perform when the EPC device has established a
+ connection with a host system
+
+ 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().
+
+2.2.2 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.
+
+2.2.2 Other 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 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.
--
2.11.0