Badhri Jagan Sridharan d3d959404e tcpm: Implement sink support for PD SPR AVS negotiation
Add support to enable TCPM to negotiate with
USB PD Standard Power Range Adjustable Voltage Supply (SPR AVS) when
acting as a power sink.

* Added support to the tcpm power supply properties, allowing userspace
  to enable and control the dynamic limits (voltage and current)
  specific to the SPR AVS contract.
* Implemented tcpm_pd_select_spr_avs_apdo() to select the appropriate
  APDO and validate the requested voltage/current against both the
  Source and Sink capabilities.
* Implemented tcpm_pd_build_spr_avs_request() to construct the
  Request Data Object (RDO) for SPR AVS.
* Added SNK_NEGOTIATE_SPR_AVS_CAPABILITIES state to the state machine to
  handle negotiation for SPR AVS.
* Updated the SNK_TRANSITION_SINK state to implement the SPR
  AVS-specific VBUS transition rules, including reducing current draw to
  PD_I_SNK_STBY_MA for large voltage changes, as required by USB PD spec.

Log stub captured when enabling AVS:
$ echo 3 > /sys/class/power_supply/tcpm-source-psy-1-0025/online
$ cat /d/usb/tcpm-1-0025/log
[  358.895775] request to set AVS online
[  358.895792] AMS POWER_NEGOTIATION start
[  358.895806] state change SNK_READY -> AMS_START [rev3 POWER_NEGOTIATION]
[  358.895850] state change AMS_START -> SNK_NEGOTIATE_SPR_AVS_CAPABILITIES [rev3 POWER_NEGOTIATION]
[  358.895866] SPR AVS src_pdo_index:4 snk_pdo_index:2 req_op_curr_ma roundup:2200 req_out_volt_mv roundup:9000
[  358.895880] Requesting APDO SPR AVS 4: 9000 mV, 2200 mA
[  358.896405] set_auto_vbus_discharge_threshold mode:0 pps_active:n vbus:0 pps_apdo_min_volt:0 ret:0
[  358.896422] PD TX, header: 0x1a82
[  358.900158] PD TX complete, status: 0
[  358.900205] pending state change SNK_NEGOTIATE_SPR_AVS_CAPABILITIES -> HARD_RESET_SEND @ 60 ms [rev3 POWER_NEGOTIATION]
[  358.904832] PD RX, header: 0x1a3 [1]
[  358.904854] state change SNK_NEGOTIATE_SPR_AVS_CAPABILITIES -> SNK_TRANSITION_SINK [rev3 POWER_NEGOTIATION]
[  358.904888] pending state change SNK_TRANSITION_SINK -> HARD_RESET_SEND @ 700 ms [rev3 POWER_NEGOTIATION]
[  359.021530] PD RX, header: 0x3a6 [1]
[  359.021546] Setting voltage/current limit 9000 mV 2200 mA
[  359.023035] set_auto_vbus_discharge_threshold mode:3 pps_active:n vbus:9000 pps_apdo_min_volt:0 ret:0
[  359.023053] state change SNK_TRANSITION_SINK -> SNK_READY [rev3 POWER_NEGOTIATION]
[  359.023090] AMS POWER_NEGOTIATION finished

$ cat /sys/class/power_supply/tcpm-source-psy-1-0025/online
3

Log stub captured when increasing voltage:
$ echo 9100000 > /sys/class/power_supply/tcpm-source-psy-1-0025/voltage_now
$ cat /d/usb/tcpm-1-0025/log

[  632.116714] AMS POWER_NEGOTIATION start
[  632.116728] state change SNK_READY -> AMS_START [rev3 POWER_NEGOTIATION]
[  632.116779] state change AMS_START -> SNK_NEGOTIATE_SPR_AVS_CAPABILITIES [rev3 POWER_NEGOTIATION]
[  632.116798] SPR AVS src_pdo_index:4 snk_pdo_index:2 req_op_curr_ma roundup:2200 req_out_volt_mv roundup:9100
[  632.116811] Requesting APDO SPR AVS 4: 9100 mV, 2200 mA
[  632.117315] set_auto_vbus_discharge_threshold mode:0 pps_active:n vbus:0 pps_apdo_min_volt:0 ret:0
[  632.117328] PD TX, header: 0x1c82
[  632.121007] PD TX complete, status: 0
[  632.121052] pending state change SNK_NEGOTIATE_SPR_AVS_CAPABILITIES -> HARD_RESET_SEND @ 60 ms [rev3 POWER_NEGOTIATION]
[  632.124572] PD RX, header: 0x5a3 [1]
[  632.124594] state change SNK_NEGOTIATE_SPR_AVS_CAPABILITIES -> SNK_TRANSITION_SINK [rev3 POWER_NEGOTIATION]
[  632.124623] pending state change SNK_TRANSITION_SINK -> HARD_RESET_SEND @ 700 ms [rev3 POWER_NEGOTIATION]
[  632.149256] PD RX, header: 0x7a6 [1]
[  632.149271] Setting voltage/current limit 9100 mV 2200 mA
[  632.150770] set_auto_vbus_discharge_threshold mode:3 pps_active:n vbus:9100 pps_apdo_min_volt:0 ret:0
[  632.150787] state change SNK_TRANSITION_SINK -> SNK_READY [rev3 POWER_NEGOTIATION]
[  632.150823] AMS POWER_NEGOTIATION finished

$ cat /sys/class/power_supply/tcpm-source-psy-1-0025/voltage_now
9100000

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Amit Sunil Dhamne <amitsd@google.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260316150301.3892223-4-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-03-18 16:08:39 +01:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2026-03-15 13:52:05 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst
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