1 # SPDX-License-Identifier: GPL-2.0+ 2 # 3 # (C) Copyright 2015 4 # Texas Instruments Incorporated - http://www.ti.com/ 5 # 6 7 Remote Processor Framework 8 ========================== 9 TOC: 10 1. Introduction 11 2. How does it work - The driver 12 3. Describing the device using platform data 13 4. Describing the device using device tree 14 15 1. Introduction 16 =============== 17 18 This is an introduction to driver-model for Remote Processors found 19 on various System on Chip(SoCs). The term remote processor is used to 20 indicate that this is not the processor on which U-Boot is operating 21 on, instead is yet another processing entity that may be controlled by 22 the processor on which we are functional. 23 24 The simplified model depends on a single UCLASS - UCLASS_REMOTEPROC 25 26 UCLASS_REMOTEPROC: 27 - drivers/remoteproc/rproc-uclass.c 28 - include/remoteproc.h 29 30 Commands: 31 - common/cmd_remoteproc.c 32 33 Configuration: 34 CONFIG_REMOTEPROC is selected by drivers as needed 35 CONFIG_CMD_REMOTEPROC for the commands if required. 36 37 2. How does it work - The driver 38 ================================= 39 40 Overall, the driver statemachine transitions are typically as follows: 41 (entry) 42 +-------+ 43 +---+ init | 44 | | | <---------------------+ 45 | +-------+ | 46 | | 47 | | 48 | +--------+ | 49 Load| | reset | | 50 | | | <----------+ | 51 | +--------+ | | 52 | |Load | | 53 | | | | 54 | +----v----+ reset | | 55 +-> | | (opt) | | 56 | Loaded +-----------+ | 57 | | | 58 +----+----+ | 59 | Start | 60 +---v-----+ (opt) | 61 +->| Running | Stop | 62 Ping +- | +--------------------+ 63 (opt) +---------+ 64 65 (is_running does not change state) 66 opt: Optional state transition implemented by driver. 67 68 NOTE: It depends on the remote processor as to the exact behavior 69 of the statemachine, remoteproc core does not intent to implement 70 statemachine logic. Certain processors may allow start/stop without 71 reloading the image in the middle, certain other processors may only 72 allow us to start the processor(image from a EEPROM/OTP) etc. 73 74 It is hence the responsibility of the driver to handle the requisite 75 state transitions of the device as necessary. 76 77 Basic design assumptions: 78 79 Remote processor can operate on a certain firmware that maybe loaded 80 and released from reset. 81 82 The driver follows a standard UCLASS DM. 83 84 in the bare minimum form: 85 86 static const struct dm_rproc_ops sandbox_testproc_ops = { 87 .load = sandbox_testproc_load, 88 .start = sandbox_testproc_start, 89 }; 90 91 static const struct udevice_id sandbox_ids[] = { 92 {.compatible = "sandbox,test-processor"}, 93 {} 94 }; 95 96 U_BOOT_DRIVER(sandbox_testproc) = { 97 .name = "sandbox_test_proc", 98 .of_match = sandbox_ids, 99 .id = UCLASS_REMOTEPROC, 100 .ops = &sandbox_testproc_ops, 101 .probe = sandbox_testproc_probe, 102 }; 103 104 This allows for the device to be probed as part of the "init" command 105 or invocation of 'rproc_init()' function as the system dependencies define. 106 107 The driver is expected to maintain it's own statemachine which is 108 appropriate for the device it maintains. It must, at the very least 109 provide a load and start function. We assume here that the device 110 needs to be loaded and started, else, there is no real purpose of 111 using the remoteproc framework. 112 113 3. Describing the device using platform data 114 ============================================ 115 116 *IMPORTANT* NOTE: THIS SUPPORT IS NOT MEANT FOR USE WITH NEWER PLATFORM 117 SUPPORT. THIS IS ONLY FOR LEGACY DEVICES. THIS MODE OF INITIALIZATION 118 *WILL* BE EVENTUALLY REMOVED ONCE ALL NECESSARY PLATFORMS HAVE MOVED 119 TO DM/FDT. 120 121 Considering that many platforms are yet to move to device-tree model, 122 a simplified definition of a device is as follows: 123 124 struct dm_rproc_uclass_pdata proc_3_test = { 125 .name = "proc_3_legacy", 126 .mem_type = RPROC_INTERNAL_MEMORY_MAPPED, 127 .driver_plat_data = &mydriver_data; 128 }; 129 130 U_BOOT_DEVICE(proc_3_demo) = { 131 .name = "sandbox_test_proc", 132 .platdata = &proc_3_test, 133 }; 134 135 There can be additional data that may be desired depending on the 136 remoteproc driver specific needs (for example: SoC integration 137 details such as clock handle or something similar). See appropriate 138 documentation for specific remoteproc driver for further details. 139 These are passed via driver_plat_data. 140 141 3. Describing the device using device tree 142 ========================================== 143 / { 144 ... 145 aliases { 146 ... 147 remoteproc0 = &rproc_1; 148 remoteproc1 = &rproc_2; 149 150 }; 151 ... 152 153 rproc_1: rproc@1 { 154 compatible = "sandbox,test-processor"; 155 remoteproc-name = "remoteproc-test-dev1"; 156 }; 157 158 rproc_2: rproc@2 { 159 compatible = "sandbox,test-processor"; 160 internal-memory-mapped; 161 remoteproc-name = "remoteproc-test-dev2"; 162 }; 163 ... 164 }; 165 166 aliases usage is optional, but it is usually recommended to ensure the 167 users have a consistent usage model for a platform. 168 the compatible string used here is specific to the remoteproc driver involved. 169