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diff --git a/Documentation/devicetree/bindings/fpga/fpga-region.yaml b/Documentation/devicetree/bindings/fpga/fpga-region.yaml new file mode 100644 index 000000000000..77554885a6c4 --- /dev/null +++ b/Documentation/devicetree/bindings/fpga/fpga-region.yaml @@ -0,0 +1,358 @@ +# SPDX-License-Identifier: GPL-2.0 +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/fpga/fpga-region.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: FPGA Region + +maintainers: + - Michal Simek <[email protected]> + +description: | + CONTENTS + - Introduction + - Terminology + - Sequence + - FPGA Region + - Supported Use Models + - Constraints + + + Introduction + ============ + + FPGA Regions represent FPGA's and partial reconfiguration regions of FPGA's in + the Device Tree. FPGA Regions provide a way to program FPGAs under device tree + control. + + The documentation hits some of the high points of FPGA usage and + attempts to include terminology used by both major FPGA manufacturers. This + document isn't a replacement for any manufacturers specifications for FPGA + usage. + + + Terminology + =========== + + Full Reconfiguration + * The entire FPGA is programmed. + + Partial Reconfiguration (PR) + * A section of an FPGA is reprogrammed while the rest of the FPGA is not + affected. + * Not all FPGA's support PR. + + Partial Reconfiguration Region (PRR) + * Also called a "reconfigurable partition" + * A PRR is a specific section of an FPGA reserved for reconfiguration. + * A base (or static) FPGA image may create a set of PRR's that later may + be independently reprogrammed many times. + * The size and specific location of each PRR is fixed. + * The connections at the edge of each PRR are fixed. The image that is loaded + into a PRR must fit and must use a subset of the region's connections. + * The busses within the FPGA are split such that each region gets its own + branch that may be gated independently. + + Persona + * Also called a "partial bit stream" + * An FPGA image that is designed to be loaded into a PRR. There may be + any number of personas designed to fit into a PRR, but only one at a time + may be loaded. + * A persona may create more regions. + + FPGA Bridge + * FPGA Bridges gate bus signals between a host and FPGA. + * FPGA Bridges should be disabled while the FPGA is being programmed to + prevent spurious signals on the cpu bus and to the soft logic. + * FPGA bridges may be actual hardware or soft logic on an FPGA. + * During Full Reconfiguration, hardware bridges between the host and FPGA + will be disabled. + * During Partial Reconfiguration of a specific region, that region's bridge + will be used to gate the busses. Traffic to other regions is not affected. + * In some implementations, the FPGA Manager transparently handles gating the + buses, eliminating the need to show the hardware FPGA bridges in the + device tree. + * An FPGA image may create a set of reprogrammable regions, each having its + own bridge and its own split of the busses in the FPGA. + + FPGA Manager + * An FPGA Manager is a hardware block that programs an FPGA under the control + of a host processor. + + Base Image + * Also called the "static image" + * An FPGA image that is designed to do full reconfiguration of the FPGA. + * A base image may set up a set of partial reconfiguration regions that may + later be reprogrammed. + + ---------------- ---------------------------------- + | Host CPU | | FPGA | + | | | | + | ----| | ----------- -------- | + | | H | | |==>| Bridge0 |<==>| PRR0 | | + | | W | | | ----------- -------- | + | | | | | | + | | B |<=====>|<==| ----------- -------- | + | | R | | |==>| Bridge1 |<==>| PRR1 | | + | | I | | | ----------- -------- | + | | D | | | | + | | G | | | ----------- -------- | + | | E | | |==>| Bridge2 |<==>| PRR2 | | + | ----| | ----------- -------- | + | | | | + ---------------- ---------------------------------- + + Figure 1: An FPGA set up with a base image that created three regions. Each + region (PRR0-2) gets its own split of the busses that is independently gated by + a soft logic bridge (Bridge0-2) in the FPGA. The contents of each PRR can be + reprogrammed independently while the rest of the system continues to function. + + + Sequence + ======== + + When a DT overlay that targets an FPGA Region is applied, the FPGA Region will + do the following: + + 1. Disable appropriate FPGA bridges. + 2. Program the FPGA using the FPGA manager. + 3. Enable the FPGA bridges. + 4. The Device Tree overlay is accepted into the live tree. + 5. Child devices are populated. + + When the overlay is removed, the child nodes will be removed and the FPGA Region + will disable the bridges. + + + FPGA Region + =========== + + FPGA Regions represent FPGA's and FPGA PR regions in the device tree. An FPGA + Region brings together the elements needed to program on a running system and + add the child devices: + + * FPGA Manager + * FPGA Bridges + * image-specific information needed to the programming. + * child nodes + + The intended use is that a Device Tree overlay (DTO) can be used to reprogram an + FPGA while an operating system is running. + + An FPGA Region that exists in the live Device Tree reflects the current state. + If the live tree shows a "firmware-name" property or child nodes under an FPGA + Region, the FPGA already has been programmed. A DTO that targets an FPGA Region + and adds the "firmware-name" property is taken as a request to reprogram the + FPGA. After reprogramming is successful, the overlay is accepted into the live + tree. + + The base FPGA Region in the device tree represents the FPGA and supports full + reconfiguration. It must include a phandle to an FPGA Manager. The base + FPGA region will be the child of one of the hardware bridges (the bridge that + allows register access) between the cpu and the FPGA. If there are more than + one bridge to control during FPGA programming, the region will also contain a + list of phandles to the additional hardware FPGA Bridges. + + For partial reconfiguration (PR), each PR region will have an FPGA Region. + These FPGA regions are children of FPGA bridges which are then children of the + base FPGA region. The "Full Reconfiguration to add PRR's" example below shows + this. + + If an FPGA Region does not specify an FPGA Manager, it will inherit the FPGA + Manager specified by its ancestor FPGA Region. This supports both the case + where the same FPGA Manager is used for all of an FPGA as well the case where + a different FPGA Manager is used for each region. + + FPGA Regions do not inherit their ancestor FPGA regions' bridges. This prevents + shutting down bridges that are upstream from the other active regions while one + region is getting reconfigured (see Figure 1 above). During PR, the FPGA's + hardware bridges remain enabled. The PR regions' bridges will be FPGA bridges + within the static image of the FPGA. + + + Supported Use Models + ==================== + + In all cases the live DT must have the FPGA Manager, FPGA Bridges (if any), and + a FPGA Region. The target of the Device Tree Overlay is the FPGA Region. Some + uses are specific to an FPGA device. + + * No FPGA Bridges + In this case, the FPGA Manager which programs the FPGA also handles the + bridges behind the scenes. No FPGA Bridge devices are needed for full + reconfiguration. + + * Full reconfiguration with hardware bridges + In this case, there are hardware bridges between the processor and FPGA that + need to be controlled during full reconfiguration. Before the overlay is + applied, the live DT must include the FPGA Manager, FPGA Bridges, and a + FPGA Region. The FPGA Region is the child of the bridge that allows + register access to the FPGA. Additional bridges may be listed in a + fpga-bridges property in the FPGA region or in the device tree overlay. + + * Partial reconfiguration with bridges in the FPGA + In this case, the FPGA will have one or more PRR's that may be programmed + separately while the rest of the FPGA can remain active. To manage this, + bridges need to exist in the FPGA that can gate the buses going to each FPGA + region while the buses are enabled for other sections. Before any partial + reconfiguration can be done, a base FPGA image must be loaded which includes + PRR's with FPGA bridges. The device tree should have an FPGA region for each + PRR. + + Constraints + =========== + + It is beyond the scope of this document to fully describe all the FPGA design + constraints required to make partial reconfiguration work[1] [2] [3], but a few + deserve quick mention. + + A persona must have boundary connections that line up with those of the partition + or region it is designed to go into. + + During programming, transactions through those connections must be stopped and + the connections must be held at a fixed logic level. This can be achieved by + FPGA Bridges that exist on the FPGA fabric prior to the partial reconfiguration. + + -- + [1] www.altera.com/content/dam/altera-www/global/en_US/pdfs/literature/ug/ug_partrecon.pdf + [2] tspace.library.utoronto.ca/bitstream/1807/67932/1/Byma_Stuart_A_201411_MAS_thesis.pdf + [3] https://www.xilinx.com/support/documentation/sw_manuals/xilinx14_1/ug702.pdf + +properties: + $nodename: + pattern: "^fpga-region(@.*|-([0-9]|[1-9][0-9]+))?$" + + compatible: + const: fpga-region + + reg: + maxItems: 1 + + ranges: true + "#address-cells": true + "#size-cells": true + + config-complete-timeout-us: + description: + The maximum time in microseconds time for the FPGA to go to operating + mode after the region has been programmed. + + encrypted-fpga-config: + type: boolean + description: + Set if the bitstream is encrypted. + + external-fpga-config: + type: boolean + description: + Set if the FPGA has already been configured prior to OS boot up. + + firmware-name: + maxItems: 1 + description: + Should contain the name of an FPGA image file located on the firmware + search path. If this property shows up in a live device tree it indicates + that the FPGA has already been programmed with this image. + If this property is in an overlay targeting an FPGA region, it is + a request to program the FPGA with that image. + + fpga-bridges: + $ref: /schemas/types.yaml#/definitions/phandle-array + description: + Should contain a list of phandles to FPGA Bridges that must be + controlled during FPGA programming along with the parent FPGA bridge. + This property is optional if the FPGA Manager handles the bridges. + If the fpga-region is the child of an fpga-bridge, the list should not + contain the parent bridge. + + fpga-mgr: + $ref: /schemas/types.yaml#/definitions/phandle + description: + Should contain a phandle to an FPGA Manager. Child FPGA Regions + inherit this property from their ancestor regions. An fpga-mgr property + in a region will override any inherited FPGA manager. + + partial-fpga-config: + type: boolean + description: + Set if partial reconfiguration is to be done, otherwise full + reconfiguration is done. + + region-freeze-timeout-us: + description: + The maximum time in microseconds to wait for bridges to successfully + become disabled before the region has been programmed. + + region-unfreeze-timeout-us: + description: + The maximum time in microseconds to wait for bridges to successfully + become enabled after the region has been programmed. + +required: + - compatible + - fpga-mgr + +additionalProperties: + type: object + +examples: + - | + /* + * Full Reconfiguration without Bridges with DT overlay + */ + fpga_region0: fpga-region@0 { + compatible = "fpga-region"; + reg = <0 0>; + #address-cells = <1>; + #size-cells = <1>; + fpga-mgr = <&fpga_mgr0>; + ranges = <0x10000000 0x20000000 0x10000000>; + + /* DT Overlay contains: &fpga_region0 */ + firmware-name = "zynq-gpio.bin"; + gpio@40000000 { + compatible = "xlnx,xps-gpio-1.00.a"; + reg = <0x40000000 0x10000>; + gpio-controller; + #gpio-cells = <2>; + }; + }; + + - | + /* + * Partial reconfiguration with bridge + */ + fpga_region1: fpga-region@0 { + compatible = "fpga-region"; + reg = <0 0>; + ranges; + #address-cells = <1>; + #size-cells = <1>; + fpga-mgr = <&fpga_mgr1>; + fpga-bridges = <&fpga_bridge1>; + partial-fpga-config; + + /* DT Overlay contains: &fpga_region1 */ + firmware-name = "zynq-gpio-partial.bin"; + clk: clock { + compatible = "fixed-factor-clock"; + clocks = <&parentclk>; + #clock-cells = <0>; + clock-div = <2>; + clock-mult = <1>; + }; + axi { + compatible = "simple-bus"; + #address-cells = <1>; + #size-cells = <1>; + ranges; + gpio@40000000 { + compatible = "xlnx,xps-gpio-1.00.a"; + reg = <0x40000000 0x10000>; + #gpio-cells = <2>; + gpio-controller; + clocks = <&clk>; + }; + }; + }; |