Analysis of Linux PMBus bus drive design

Tag: Set characteristic standard response latest ATI up and down intelligent AVS

PMBus Protocol Specification Introduction

PMBus is a set of communication protocol standards for the configuration, control and monitoring of power supplies. The latest version is 1.3, and the specification is evolving, such as the new zone PMBus, Avsbus, and other features. There is a detailed specification document on its official website, this section does not attempt to translate the specification document, focus on the author's understanding of the pmbus process of questions and answers.

What is the difference between PMBus and I²c and SMBus?

PMBus adds a set of power configuration, control, and monitoring specifications based on the SMBus (System Management Bus). SMBus was originally developed for battery Intelligence management based on the I²C protocol, and the following improvements were made to the weak robustness of the I²C protocol:

• Support smbalert# interrupt;
• Support for error packet detection (PEC);
• When supporting Fengliang;
• Support Start/stop protection;
• Support Host Notify Protocol protocol;

What parameters does the PMBus monitor? What are the levels of alarms? What are the countermeasures for different alarm levels?

The PMBus supports up-and-down monitoring of parameters such as voltage, current, power, temperature, and fan, and supports the warning and fault level 2 alarm levels (as shown).

• Warning Alarm: Indicates abnormal monitoring parameters, the system needs to cause concern, but can continue to operate, the system does not need any response measures;
• Fault alarm: higher than the warning alarm level, the system will be based on the abnormal damage to the equipment, equipment control circuit restart (restart) or output cut off (shutdown) and other processing;

How to report to the host when the alarm is generated?

Alarm escalation generally has the following methods:

• Host polling PMBus device;
• PMBus Equipment through smbalert# interrupt notification host;
• Host Notify Protocol (PMBus device temporarily switches to bus master and sends a specific set of protocols to notify the system host).

What happens when the alarm is canceled or cleared? Does restarting erase alarms?

If any warning or fault alarms are reported, the purge can only be canceled by the following methods:

• The PMBus device receives the CLEAR_FAULTS command;
• PMBus device reset pin is in effect;
• The PMBus device is closed and reopened via the control PIN or the operation command;
• Power
• If the exception persists, the alarm will be escalated immediately, even if the alarm is cleared.

Analysis of Linux PMBus drive design

Analysis of Linux PMBus bus drive design