9be82a4209
The list-based DMA engine has the following behaviour:
* When the DMA engine is in the init state, you can write the first
descriptor address to the QCU TxDP register and it will work.
* Then when it hits the end of the list (ie, it either hits a NULL
link pointer, OR it hits a descriptor with VEOL set) the QCU
stops, and the TxDP points to the last descriptor that was transmitted.
* Then when you want to transmit a new frame, you can then either:
+ write the head of the new list into TxDP, or
+ you write the head of the new list into the link pointer of the
last completed descriptor (ie, where TxDP points), then kick
TxE to restart transmission on that QCU>
* The hardware then will re-read the descriptor to pick up the link
pointer and then jump to that.
Now, the quirks:
* If you write a TxDP when there's been no previous TxDP (ie, it's 0),
it works.
* If you write a TxDP in any other instance, the TxDP write may actually
fail. Thus, when you start transmission, it will re-read the last
transmitted descriptor to get the link pointer, NOT just start a new
transmission.
So the correct thing to do here is:
* ALWAYS use the holding descriptor (ie, the last transmitted descriptor
that we've kept safe) and use the link pointer in _THAT_ to transmit
the next frame.
* NEVER write to the TxDP after you've done the initial write.
* .. also, don't do this whilst you're also resetting the NIC.
With this in mind, the following patch does basically the above.
* Since this encapsulates Sam's issues with the QCU behaviour w/ TDMA,
kill the TDMA special case and replace it with the above.
* Add a new TXQ flag - PUTRUNNING - which indicates that we've started
DMA.
* Clear that flag when DMA has been shutdown.
* Ensure that we're not restarting DMA with PUTRUNNING enabled.
* Fix the link pointer logic during TXQ drain - we should always ensure
the link pointer does point to something if there's a list of frames.
Having it be NULL as an indication that DMA has finished or during
a reset causes trouble.
Now, given all of this, i want to nuke axq_link from orbit. There's now HAL
methods to get and set the link pointer of a descriptor, so what we
should do instead is to update the right link pointer.
* If there's a holding descriptor and an empty TXQ list, set the
link pointer of said holding descriptor to the new frame.
* If there's a non-empty TXQ list, set the link pointer of the
last descriptor in the list to the new frame.
* Nuke axq_link from orbit.
Note:
* The AR9380 doesn't need this. FIFO TX writes are atomic. As long as
we don't append to a list of frames that we've already passed to the
hardware, all of the above doesn't apply. The holding descriptor stuff
is still needed to ensure the hardware can re-read a completed
descriptor to move onto the next one, but we restart DMA by pushing in
a new FIFO entry into the TX QCU. That doesn't require any real
gymnastics.
Tested:
* AR5210, AR5211, AR5212, AR5416, AR9380 - STA mode.
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``world'' target should only be used in cases where the source tree has not changed from the currently running version. See: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. cddl Various commands and libraries under the Common Development and Distribution License. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. rescue Build system for statically linked /rescue utilities. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html