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f2cca20f1f
The device lock is used to serialize the low level power sequencing
operations. Since drm_helper_hpd_irq_event() could end up calling
.atomic_enable, which also calls power sequencing functions through
runtime PM, this results in a real deadlock. This was observed on an
MT8192-based Chromebook's external display (with appropriate patches [1]
and DT changes applied).
Move the drm_helper_hpd_irq_event() call outside of the lock range. The
lock only needs to be held so that the device status can be read back.
This is the bare minimum change to avoid the deadlock. The lock could
be dropped completely and have pm_runtime_get_if_in_use() increase the
reference count, but this is not the same as pm_runtime_suspended().
Dropping the lock completely also causes the internal display of the
same device to not function correctly if the internal bridge's
interrupt line is added in the device tree. Both the internal and
external display of said device each use one anx7625 bridge.
[1] https://lore.kernel.org/dri-devel/20230112042104.4107253-1-treapking@chromium.org/
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.