mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-17 08:43:07 +00:00
5ce319133b
These docs are useful for developers, not users. Move them under that section. Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Signed-off-by: Simon Glass <sjg@chromium.org>
169 lines
5.1 KiB
ReStructuredText
169 lines
5.1 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
|
|
.. (C) Copyright 2015
|
|
.. Texas Instruments Incorporated - http://www.ti.com/
|
|
|
|
Remote Processor Framework
|
|
==========================
|
|
|
|
Introduction
|
|
------------
|
|
|
|
This is an introduction to driver-model for Remote Processors found
|
|
on various System on Chip(SoCs). The term remote processor is used to
|
|
indicate that this is not the processor on which U-Boot is operating
|
|
on, instead is yet another processing entity that may be controlled by
|
|
the processor on which we are functional.
|
|
|
|
The simplified model depends on a single UCLASS - UCLASS_REMOTEPROC
|
|
|
|
UCLASS_REMOTEPROC:
|
|
- drivers/remoteproc/rproc-uclass.c
|
|
- include/remoteproc.h
|
|
|
|
Commands:
|
|
- common/cmd_remoteproc.c
|
|
|
|
Configuration:
|
|
- CONFIG_REMOTEPROC is selected by drivers as needed
|
|
- CONFIG_CMD_REMOTEPROC for the commands if required.
|
|
|
|
How does it work - The driver
|
|
-----------------------------
|
|
|
|
Overall, the driver statemachine transitions are typically as follows::
|
|
|
|
(entry)
|
|
+-------+
|
|
+---+ init |
|
|
| | | <---------------------+
|
|
| +-------+ |
|
|
| |
|
|
| |
|
|
| +--------+ |
|
|
Load| | reset | |
|
|
| | | <----------+ |
|
|
| +--------+ | |
|
|
| |Load | |
|
|
| | | |
|
|
| +----v----+ reset | |
|
|
+-> | | (opt) | |
|
|
| Loaded +-----------+ |
|
|
| | |
|
|
+----+----+ |
|
|
| Start |
|
|
+---v-----+ (opt) |
|
|
+->| Running | Stop |
|
|
Ping +- | +--------------------+
|
|
(opt) +---------+
|
|
|
|
(is_running does not change state)
|
|
opt: Optional state transition implemented by driver.
|
|
|
|
NOTE: It depends on the remote processor as to the exact behavior
|
|
of the statemachine, remoteproc core does not intent to implement
|
|
statemachine logic. Certain processors may allow start/stop without
|
|
reloading the image in the middle, certain other processors may only
|
|
allow us to start the processor(image from a EEPROM/OTP) etc.
|
|
|
|
It is hence the responsibility of the driver to handle the requisite
|
|
state transitions of the device as necessary.
|
|
|
|
Basic design assumptions:
|
|
|
|
Remote processor can operate on a certain firmware that maybe loaded
|
|
and released from reset.
|
|
|
|
The driver follows a standard UCLASS DM.
|
|
|
|
in the bare minimum form:
|
|
|
|
.. code-block:: c
|
|
|
|
static const struct dm_rproc_ops sandbox_testproc_ops = {
|
|
.load = sandbox_testproc_load,
|
|
.start = sandbox_testproc_start,
|
|
};
|
|
|
|
static const struct udevice_id sandbox_ids[] = {
|
|
{.compatible = "sandbox,test-processor"},
|
|
{}
|
|
};
|
|
|
|
U_BOOT_DRIVER(sandbox_testproc) = {
|
|
.name = "sandbox_test_proc",
|
|
.of_match = sandbox_ids,
|
|
.id = UCLASS_REMOTEPROC,
|
|
.ops = &sandbox_testproc_ops,
|
|
.probe = sandbox_testproc_probe,
|
|
};
|
|
|
|
This allows for the device to be probed as part of the "init" command
|
|
or invocation of 'rproc_init()' function as the system dependencies define.
|
|
|
|
The driver is expected to maintain it's own statemachine which is
|
|
appropriate for the device it maintains. It must, at the very least
|
|
provide a load and start function. We assume here that the device
|
|
needs to be loaded and started, else, there is no real purpose of
|
|
using the remoteproc framework.
|
|
|
|
Describing the device using platform data
|
|
-----------------------------------------
|
|
|
|
*IMPORTANT* NOTE: THIS SUPPORT IS NOT MEANT FOR USE WITH NEWER PLATFORM
|
|
SUPPORT. THIS IS ONLY FOR LEGACY DEVICES. THIS MODE OF INITIALIZATION
|
|
*WILL* BE EVENTUALLY REMOVED ONCE ALL NECESSARY PLATFORMS HAVE MOVED
|
|
TO DM/FDT.
|
|
|
|
Considering that many platforms are yet to move to device-tree model,
|
|
a simplified definition of a device is as follows:
|
|
|
|
.. code-block:: c
|
|
|
|
struct dm_rproc_uclass_pdata proc_3_test = {
|
|
.name = "proc_3_legacy",
|
|
.mem_type = RPROC_INTERNAL_MEMORY_MAPPED,
|
|
.driver_plat_data = &mydriver_data;
|
|
};
|
|
|
|
U_BOOT_DRVINFO(proc_3_demo) = {
|
|
.name = "sandbox_test_proc",
|
|
.plat = &proc_3_test,
|
|
};
|
|
|
|
There can be additional data that may be desired depending on the
|
|
remoteproc driver specific needs (for example: SoC integration
|
|
details such as clock handle or something similar). See appropriate
|
|
documentation for specific remoteproc driver for further details.
|
|
These are passed via driver_plat_data.
|
|
|
|
Describing the device using device tree
|
|
---------------------------------------
|
|
|
|
.. code-block: none
|
|
|
|
/ {
|
|
...
|
|
aliases {
|
|
...
|
|
remoteproc0 = &rproc_1;
|
|
remoteproc1 = &rproc_2;
|
|
|
|
};
|
|
...
|
|
|
|
rproc_1: rproc@1 {
|
|
compatible = "sandbox,test-processor";
|
|
remoteproc-name = "remoteproc-test-dev1";
|
|
};
|
|
|
|
rproc_2: rproc@2 {
|
|
compatible = "sandbox,test-processor";
|
|
internal-memory-mapped;
|
|
remoteproc-name = "remoteproc-test-dev2";
|
|
};
|
|
...
|
|
};
|
|
|
|
aliases usage is optional, but it is usually recommended to ensure the
|
|
users have a consistent usage model for a platform.
|
|
the compatible string used here is specific to the remoteproc driver involved.
|