95dcd64bc5
Technically this is not required because disabling the PWM should be enough. However, when support for atomic operations was implemented in the PWM subsystem, only actual changes to the PWM channel are applied during pwm_config(), which means that during after resume from suspend the old settings won't be applied. One possible solution is for the PWM driver to implement its own PM operations such that settings from before suspend get applied on resume. This has the disadvantage of completely ignoring any particular ordering requirements that PWM user drivers might have, so it is best to leave it up to the user drivers to apply the settings that they want at the appropriate time. Another way to solve this would be to read back the current state of the PWM at the time of resume. That way, in case the configuration was lost during suspend, applying the old settings in PWM user drivers would actually get them applied because they differ from the current settings. However, not all PWM drivers support reading the hardware state, and not all hardware may support it. The best workaround at this point seems to be to let PWM user drivers tell the PWM subsystem that the PWM is turned off by, in addition to disabling it, also setting the duty cycle to 0. This causes the resume operation to apply a configuration that is different from the current configuration, resulting in the proper state from before suspend getting restored. Signed-off-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.