ea93ed4c18
The EOQ mode has a hardware limitation in that it stops the transmission (including the deassertion of the chip select signal) once the host CPU requests end-of-queue for a particular word in the TX FIFO. And XSPI mode has a limitation in that we need a separate CMD FIFO entry for the last byte in the buffer, where the chip select signal needs to be deasserted. It's not a functional limitation, but it's rather clunky and the fact that we need to halt the pipeline and write a single entry to the TX FIFO whenever a buffer ends brings the throughput down when transmitting small buffers. So the idea here is to use EOQ's limitation in our favor when using XSPI mode. Stop special-casing that final word in the buffer, and just kill the chip select signal by issuing an EOQ for that last word. Now it can be mixed in with all the other words in the current TX FIFO train. A small trick here is that we still keep using the XSPI-specific signaling via the CMDTCFQ interrupt in RSER, and not enabling the EOQ interrupt, in order to avoid hardware weirdness (potential races with separate interrupts being raised for CMDTCFQ and EOQ for what is in fact the end of the same transmission). That is just theoretical, but it's good to be cautious, and the EOQ interrupt isn't needed. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://lore.kernel.org/r/20200304220044.11193-12-olteanv@gmail.com Signed-off-by: Mark Brown <broonie@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.