Eric Neulight 436418ef5b arm64: dts: amlogic: meson-sm1-odroid: Eliminate Odroid HC4 power glitches during boot.
Fix issue with Odroid HC4 (and all meson-sm1-odroid) DTS that causes
regulator power to momentarily glitch OFF-ON during boot.  Add
regulator-boot-on to all regulator-fixed and regulator-gpio entries
that (1) define a gpio AND (2) define regulator-always-on.

U-boot powers on devices necessary for boot then hands off the DTB to
the kernel.  During probe, linux drivers/regulator/fixed.c and
gpio-regulator.c both first set the regulator control gpio (that U-boot
already turned ON) to default OFF before then setting it to the defined
(ON) state. This glitches the power to the affected devices, unless
regulator-boot-on is specified with it.  In fact, U-boot has the same
behavior.  So, during reboot, a power glitch can actually happen twice:
once when U-boot reads the DTB and probes the gpio and again when the
kernel reads the DTB and probes the gpio.

Problem this fixes: On the Odroid HC4, power to the SATA ports glitches
during boot and causes some HDDs to do emergency head retract, which
should be avoided.  On the HC4, power glitches to the SD card, USB,
SATA, and HDMI interfaces during boot.  These are all boot devices.
A power glitch can potentially cause a problem for any sensitive devices
during boot.

NOTE: This is not limited to just the HC4, likely an issue with ALL DTS
with regulator-fixed or regulator-gpio entries that (1) define a gpio
AND (2) define regulator-always-on.  All such entries should also
include regulator-boot-on in order to avoid potential power glitches.
At worst, adding regulator-boot-on in such cases is harmless because of
regulator-always-on, and, at best, it eliminates detrimental power
glitches during boot.  So, this is best-practice.

Fixes: 164147f094 ("arm64: dts: meson-sm1-odroid-hc4: add regulators controlled by GPIOH_8")
Fixes: 45d736ab17 ("arm64: dts: meson-sm1-odroid: add 5v regulator gpio")
Fixes: 1f80a5cf74 ("arm64: dts: meson-sm1-odroid: add missing enable gpio and supply for tf_io regulator")
Fixes: 88d537bc92 ("arm64: dts: meson: convert meson-sm1-odroid-c4 to dtsi")

Signed-off-by: Eric Neulight <Eric.Neulight@linuxdev.slmail.me>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Viacheslav Bocharov <v@baodeep.com>
Tested-by: Ricardo Pardini <ricardo@pardini.net> # on Odroid-HC4 5V HDD
Link: https://patch.msgid.link/20260116-odroid-hc4-dts-v1-1-459b601cd5cf@linuxdev.slmail.me
[narmstrong: fixed subject prefix]
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
2026-01-20 09:28:41 +01:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2025-12-14 16:05:07 +12:00

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


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



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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