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Jérôme Pouiller 102f54dc47 wifi: wfx: fix possible device hang during init
The WFxxx device provides an SDIO interface. In addition to the usual
in-band SDIO IRQ, the device also supports out-of-band IRQ line. OOB IRQ
requires a specific initialization described in commit f00dc1d789
("staging: wfx: poll IRQ during init"):

    When the chip starts in SDIO mode, the external IRQ (aka Out-Of-Band
    IRQ) cannot be used before to configure it. Therefore, the first
    exchanges with the chip have to be done without the OOB IRQ.

    This patch allow to poll the data until the OOB IRQ is correctly
    setup. In order to keep the code simpler, this patch also poll data
    even if OOB IRQ is not used.

Commit 57aa557f11 ("staging: wfx: introduce a way to poll IRQ")
announce some limitation about the data polling mechanism:

    This function [wfx_bh_poll_irq()] must used with care: if an IRQ
    fires while the host reads control register, the IRQ can be lost.

However, with last analysis, it seems it does not only impact the IRQ.
When this condition happen the hardware is lost and won't reply the next
commands. The only way to recover the error is to pull the reset pin and
bind the device again.

Currently wfx_bh_poll_irq() is only used during the two first exchanges
with the hardware. Therefore, it has been reported to only happen after
a few hours of bind/rebind in a loop. This explain why it has not been
reported before.

Fortunately, wfx_bh_poll_irq() is only required for OOB IRQ, which is
probably very marginal. The In-Band IRQ case also uses this function,
but only to simplify the code.

This patch limits the use of wfx_bh_poll_irq() to the OOB IRQ. The bus
driver now tells wfx_probe() whether polling is necessary. When it is
not (in-band SDIO IRQ and SPI), the IRQ is subscribed before the first
exchange with the device and wfx_bh_poll_irq() is never called. When it
is (SDIO with OOB IRQ), the behavior is unchanged: the control register
is polled until the PDS file has configured the IRQ line.

To conclude, In-Band users are now safe. Users of OOB IRQ will be still
impacted by the bug, but there is nothing we can do (and nobody
complained during the last 6 years).

Fixes: f00dc1d789 ("staging: wfx: poll IRQ during init")
Reported-by: Gerard Salvatella <gerard.salvatella@siemens.com>
Reported-by: Lukas Stockmann <lukas.stockmann@siemens.com>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Tested-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://patch.msgid.link/20260901083548.113131-2-jerome.pouiller@silabs.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
History 2026-09-04 10:48:49 +02:00
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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
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* System Administrator: Configuring and troubleshooting
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* 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
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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.


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=========================

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