mainlining shenanigans
ae7d2346dc
The interaction with the controller message queue and its corresponding auxiliary flags and variables requires the use of the queue_lock which is costly. Since spi_sync will transfer the complete message anyway, and not return until it is finished, there is no need to put the message into the queue if the queue is empty. This can save a lot of overhead. As an example of how significant this is, when using the MCP2518FD SPI CAN controller on a i.MX8MM SoC, the time during which the interrupt line stays active (during 3 relatively short spi_sync messages), is reduced from 98us to 72us by this patch. Signed-off-by: David Jander <david@protonic.nl> Link: https://lore.kernel.org/r/20220621061234.3626638-3-david@protonic.nl Signed-off-by: Mark Brown <broonie@kernel.org> |
||
|---|---|---|
| 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.