mainlining shenanigans
e4401abb34
The SoundWire Linux devices are created purely based on information provided by platform firmware (e.g. ACPI DSDT table). When the kernel finds a matching driver for the device address (_ADR), the probe will initialize required data structures and initialize pm ops. When the SoundWire link is started at a later point, the physical devices will synchronize on the SoundWire frames and report their attachment status, thereby triggering the enumeration and initialization of device registers. This two-step solution was a conscious design decision to allow e.g. a driver to use sideband mechanisms to turn power rails on. This can also allow OEMs to describe multiple platforms with the same DSDT table, the devices that are not physically present in hardware. The drawback of this approach is a bit of confusion, with more devices than are actually present in hardware. This results in 'ghost' devices, for which the driver successfully probes, but that will not generate any traffic on the bus. suspend-resume transitions are handled by drivers, and skipped when the devices are not physically present. This patch provides a work-around for a second-level of confusion in platform firmware: some platforms only use HDaudio links, but nevertheless expose SoundWire 'ghost' devices. This results in error messages in the Intel driver while trying to suspend/resume these links. The simplest solution is to add a boolean status flag to skip all suspend/resume/wake sequences if the link was never started. Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com> Link: https://lore.kernel.org/r/20210818024954.16873-3-yung-chuan.liao@linux.intel.com Signed-off-by: Vinod Koul <vkoul@kernel.org> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| 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.