interconnect: Add generic on-chip interconnect API

.. SPDX-License-Identifier: GPL-2.0

=====================================

GENERIC SYSTEM INTERCONNECT SUBSYSTEM

=====================================

Introduction

------------

This framework is designed to provide a standard kernel interface to control

the settings of the interconnects on an SoC. These settings can be throughput,

latency and priority between multiple interconnected devices or functional

blocks. This can be controlled dynamically in order to save power or provide

maximum performance.

The interconnect bus is hardware with configurable parameters, which can be

set on a data path according to the requests received from various drivers.

An example of interconnect buses are the interconnects between various

components or functional blocks in chipsets. There can be multiple interconnects

on an SoC that can be multi-tiered.

Below is a simplified diagram of a real-world SoC interconnect bus topology.

::

 +----------------+    +----------------+

 | HW Accelerator |--->|      M NoC     |<---------------+

 +----------------+    +----------------+                |

                         |      |                    +------------+

  +-----+  +-------------+      V       +------+     |            |

  | DDR |  |                +--------+  | PCIe |     |            |

  +-----+  |                | Slaves |  +------+     |            |

    ^ ^    |                +--------+     |         |   C NoC    |

    | |    V                               V         |            |

 +------------------+   +------------------------+   |            |   +-----+

 |                  |-->|                        |-->|            |-->| CPU |

 |                  |-->|                        |<--|            |   +-----+

 |     Mem NoC      |   |         S NoC          |   +------------+

 |                  |<--|                        |---------+    |

 |                  |<--|                        |<------+ |    |   +--------+

 +------------------+   +------------------------+       | |    +-->| Slaves |

   ^  ^    ^    ^          ^                             | |        +--------+

   |  |    |    |          |                             | V

 +------+  |  +-----+   +-----+  +---------+   +----------------+   +--------+

 | CPUs |  |  | GPU |   | DSP |  | Masters |-->|       P NoC    |-->| Slaves |

 +------+  |  +-----+   +-----+  +---------+   +----------------+   +--------+

           |

       +-------+

       | Modem |

       +-------+

Terminology

-----------

Interconnect provider is the software definition of the interconnect hardware.

The interconnect providers on the above diagram are M NoC, S NoC, C NoC, P NoC

and Mem NoC.

Interconnect node is the software definition of the interconnect hardware

port. Each interconnect provider consists of multiple interconnect nodes,

which are connected to other SoC components including other interconnect

providers. The point on the diagram where the CPUs connect to the memory is

called an interconnect node, which belongs to the Mem NoC interconnect provider.

Interconnect endpoints are the first or the last element of the path. Every

endpoint is a node, but not every node is an endpoint.

Interconnect path is everything between two endpoints including all the nodes

that have to be traversed to reach from a source to destination node. It may

include multiple master-slave pairs across several interconnect providers.

Interconnect consumers are the entities which make use of the data paths exposed

by the providers. The consumers send requests to providers requesting various

throughput, latency and priority. Usually the consumers are device drivers, that

send request based on their needs. An example for a consumer is a video decoder

that supports various formats and image sizes.

Interconnect providers

----------------------

Interconnect provider is an entity that implements methods to initialize and

configure interconnect bus hardware. The interconnect provider drivers should

be registered with the interconnect provider core.

.. kernel-doc:: include/linux/interconnect-provider.h

Interconnect consumers

----------------------

Interconnect consumers are the clients which use the interconnect APIs to

get paths between endpoints and set their bandwidth/latency/QoS requirements

for these interconnect paths.

.. kernel-doc:: include/linux/interconnect.h

source "drivers/slimbus/Kconfig"

source "drivers/interconnect/Kconfig"

endmenu

obj-$(CONFIG_UNISYS_VISORBUS)	+= visorbus/

obj-$(CONFIG_SIOX)		+= siox/

obj-$(CONFIG_GNSS)		+= gnss/

obj-$(CONFIG_INTERCONNECT)	+= interconnect/

menuconfig INTERCONNECT

	tristate "On-Chip Interconnect management support"

	help

	  Support for management of the on-chip interconnects.

	  This framework is designed to provide a generic interface for

	  managing the interconnects in a SoC.

	  If unsure, say no.

# SPDX-License-Identifier: GPL-2.0

icc-core-objs				:= core.o

obj-$(CONFIG_INTERCONNECT)		+= icc-core.o