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Niklas Cassel e9ce5b3804 Revert "PCI: qcom: Don't wait for link if we can detect Link Up"
This reverts commit 36971d6c5a.

While this fake hotplugging was a nice idea, it has shown that this feature
does not handle PCIe switches correctly:
pci_bus 0004:43: busn_res: can not insert [bus 43-41] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci_bus 0004:43: busn_res: [bus 43-41] end is updated to 43
pci_bus 0004:43: busn_res: can not insert [bus 43] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci 0004:42:00.0: devices behind bridge are unusable because [bus 43] cannot be assigned for them
pci_bus 0004:44: busn_res: can not insert [bus 44-41] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci_bus 0004:44: busn_res: [bus 44-41] end is updated to 44
pci_bus 0004:44: busn_res: can not insert [bus 44] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci 0004:42:02.0: devices behind bridge are unusable because [bus 44] cannot be assigned for them
pci_bus 0004:45: busn_res: can not insert [bus 45-41] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci_bus 0004:45: busn_res: [bus 45-41] end is updated to 45
pci_bus 0004:45: busn_res: can not insert [bus 45] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci 0004:42:06.0: devices behind bridge are unusable because [bus 45] cannot be assigned for them
pci_bus 0004:46: busn_res: can not insert [bus 46-41] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci_bus 0004:46: busn_res: [bus 46-41] end is updated to 46
pci_bus 0004:46: busn_res: can not insert [bus 46] under [bus 42-41] (conflicts with (null) [bus 42-41])
pci 0004:42:0e.0: devices behind bridge are unusable because [bus 46] cannot be assigned for them
pci_bus 0004:42: busn_res: [bus 42-41] end is updated to 46
pci_bus 0004:42: busn_res: can not insert [bus 42-46] under [bus 41] (conflicts with (null) [bus 41])
pci 0004:41:00.0: devices behind bridge are unusable because [bus 42-46] cannot be assigned for them
pcieport 0004:40:00.0: bridge has subordinate 41 but max busn 46

During the initial scan, PCI core doesn't see the switch and since the Root
Port is not hot plug capable, the secondary bus number gets assigned as the
subordinate bus number. This means, the PCI core assumes that only one bus
will appear behind the Root Port since the Root Port is not hot plug
capable.

This works perfectly fine for PCIe endpoints connected to the Root Port,
since they don't extend the bus. However, if a PCIe switch is connected,
then there is a problem when the downstream busses starts showing up and
the PCI core doesn't extend the subordinate bus number and bridge resources
after initial scan during boot.

The long term plan is to migrate this driver to the upcoming pwrctrl APIs
that are supposed to handle this problem elegantly.

Suggested-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Tested-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Shawn Lin <shawn.lin@rock-chips.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251222064207.3246632-11-cassel@kernel.org
2025-12-22 22:31:31 +05:30
arch Misc fixes: 2025-12-14 06:10:35 +12:00
block block-6.19-20251211 2025-12-12 22:04:18 +12:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Networking changes for 6.19. 2025-12-03 17:24:33 -08:00
Documentation Misc fixes: 2025-12-14 06:07:09 +12:00
drivers Revert "PCI: qcom: Don't wait for link if we can detect Link Up" 2025-12-22 22:31:31 +05:30
fs We have a patch that adds an initial set of tracepoints to the MDS 2025-12-14 15:24:10 +12:00
include We have a patch that adds an initial set of tracepoints to the MDS 2025-12-14 15:24:10 +12:00
init Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
io_uring io_uring-6.19-20251211 2025-12-12 22:01:32 +12:00
ipc Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
kernel Fix CPU hotplug callbacks to disable interrupts on UP kernels. 2025-12-14 06:12:46 +12:00
lib Miscellaneous fixes: 2025-12-14 06:04:16 +12:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm There are no significant series in this small merge. Please see the 2025-12-13 20:55:12 +12:00
net We have a patch that adds an initial set of tracepoints to the MDS 2025-12-14 15:24:10 +12:00
rust USB/Thunderbolt changes for 6.19-rc1 2025-12-06 18:42:12 -08:00
samples USB/Thunderbolt changes for 6.19-rc1 2025-12-06 18:42:12 -08:00
scripts There are no significant series in this small merge. Please see the 2025-12-13 20:55:12 +12:00
security Trivial optimization. 2025-12-14 15:21:02 +12:00
sound soundwire updates for 6.19 2025-12-13 16:26:55 +12:00
tools Futex changes for v6.19: 2025-12-10 17:21:30 +09:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt soc: driver updates for 6.19 2025-12-05 17:29:04 -08:00
.clang-format Significant patch series in this merge are as follows: 2025-12-05 13:52:43 -08:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS phy-for-6.19 2025-12-09 06:31:47 +09:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Patch series in this pull request: 2025-12-13 20:35:41 +12:00
Makefile Linux 6.19-rc1 2025-12-14 16:05:07 +12:00
README README: restructure with role-based documentation and guidelines 2025-11-29 08:40:33 -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


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