6c26b5054c
When we disable rewinds, then the .ack can be used to program SPIB with the application pointer, which allows the HDaudio DMA to save power by opportunistically bursting data transfers when the path to memory is enabled (and conversely to shut it down when there are no transfer requests). The SPIB register can only be programmed with incremental values with wrap-around after the DMA RUN bits are set. For simplicity, we set the INFO_NO_REWINDS flag in the .open callback when we already need to program the SNDRV_PCM_INFO_SYNC_APPLPTR flag. Rewinds are not used by many applications. One notable application using rewinds is PulseAudio. Practical experiments with Ubuntu/PulseAudio default settings did not show any audible issues, but the user may hear volume changes and notification with a delay, depending on the size of the ring buffer and latency constraints. The choice of disabling rewinds is exposed as a kernel parameter and not a Kconfig option to avoid any undesirable side-effects. Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com> Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com> Co-developed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Link: https://lore.kernel.org/r/20211119230852.206310-5-pierre-louis.bossart@linux.intel.com Signed-off-by: Mark Brown <broonie@kernel.org> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| 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.
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.