mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-29 22:43:10 +00:00
69 lines
2.5 KiB
ReStructuredText
69 lines
2.5 KiB
ReStructuredText
|
.. SPDX-License-Identifier: GPL-2.0+
|
||
|
|
.. (C) Copyright 2020
|
||
|
|
.. Texas Instruments Incorporated - http://www.ti.com/
|
||
|
|
|
||
|
|
SOC ID Framework
|
||
|
|
================
|
||
|
|
|
||
|
|
Introduction
|
||
|
|
------------
|
||
|
|
|
||
|
|
The driver-model SOC ID framework is able to provide identification
|
||
|
|
information about a specific SoC in use at runtime, and also provide matching
|
||
|
|
from a set of identification information from an array. This can be useful for
|
||
|
|
enabling small quirks in drivers that exist between SoC variants that are
|
||
|
|
impractical to implement using device tree flags. It is based on UCLASS_SOC.
|
||
|
|
|
||
|
|
UCLASS_SOC:
|
||
|
|
- drivers/soc/soc-uclass.c
|
||
|
|
- include/soc.h
|
||
|
|
|
||
|
|
Configuration:
|
||
|
|
- CONFIG_SOC_DEVICE is selected by drivers as needed.
|
||
|
|
|
||
|
|
Implementing a UCLASS_SOC provider
|
||
|
|
----------------------------------
|
||
|
|
|
||
|
|
The purpose of this framework is to allow UCLASS_SOC provider drivers to supply
|
||
|
|
identification information about the SoC in use at runtime. The framework
|
||
|
|
allows drivers to define soc_ops that return identification strings. All
|
||
|
|
soc_ops need not be defined and can be left as NULL, in which case the
|
||
|
|
framework will return -ENOSYS and not consider the value when doing an
|
||
|
|
soc_device_match.
|
||
|
|
|
||
|
|
It is left to the driver implementor to decide how the information returned is
|
||
|
|
determined, but in general the same SOC should always return the same set of
|
||
|
|
identifying information. Information returned must be in the form of a NULL
|
||
|
|
terminated string.
|
||
|
|
|
||
|
|
See include/soc.h for documentation of the available soc_ops and the intended
|
||
|
|
meaning of the values that can be returned. See drivers/soc/soc_sandbox.c for
|
||
|
|
an example UCLASS_SOC provider driver.
|
||
|
|
|
||
|
|
Using a UCLASS_SOC driver
|
||
|
|
-------------------------
|
||
|
|
|
||
|
|
The framework provides the ability to retrieve and use the identification
|
||
|
|
strings directly. It also has the ability to return a match from a list of
|
||
|
|
different sets of SoC data using soc_device_match.
|
||
|
|
|
||
|
|
An array of 'struct soc_attr' can be defined, each containing ID information
|
||
|
|
for a specific SoC, and when passed to soc_device_match, the identifier values
|
||
|
|
for each entry in the list will be compared against the values provided by the
|
||
|
|
UCLASS_SOC driver that is in use. The first entry in the list that matches all
|
||
|
|
non-null values will be returned by soc_device_match.
|
||
|
|
|
||
|
|
An example of various uses of the framework can be found at test/dm/soc.c.
|
||
|
|
|
||
|
|
Describing the device using device tree
|
||
|
|
---------------------------------------
|
||
|
|
|
||
|
|
.. code-block:: none
|
||
|
|
|
||
|
|
chipid: chipid {
|
||
|
|
compatible = "sandbox,soc";
|
||
|
|
};
|
||
|
|
|
||
|
|
All that is required in a DT node is a compatible for a corresponding
|
||
|
|
UCLASS_SOC driver.
|