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The QoS blocks saved/restored when toggling the PD_USB power domain are
clocked by ACLK_USB. Attempting to access these memory regions without
that clock running will result in an indefinite CPU stall.
The PD_USB node wasn't specifying this clock dependency, resulting in
hangs when trying to toggle the power domain (either on or off), unless
we get "lucky" and have ACLK_USB running for another reason at the time.
This "luck" can result from the bootloader leaving USB powered/clocked,
and if no built-in driver wants USB, Linux will disable the unused
PD+CLK on boot when {pd,clk}_ignore_unused aren't given. This can also
be unlucky because the two cleanup tasks run in parallel and race: if
the CLK is disabled first, the PD deactivation stalls the boot. In any
case, the PD cannot then be reenabled (if e.g. the driver loads later)
once the clock has been stopped.
Fix this by specifying a dependency on ACLK_USB, instead of only
ACLK_USB_ROOT. The child-parent relationship means the former implies
the latter anyway.
Fixes:
|
||
|---|---|---|
| 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.