Files
ubports_kernel_google_msm/Documentation/video4linux
Robert Jarzmik 256b02332a V4L/DVB (11321): pxa_camera: Redesign DMA handling
The DMA transfers in pxa_camera showed some weaknesses in
multiple queued buffers context :
 - poll/select problem
   The bug shows up with capture_example tool from v4l2 hg
   tree. The process just "stalls" on a "select timeout".

 - multiple buffers DMA starting
   When multiple buffers were queued, the DMA channels were
   always started right away. This is not optimal, as a
   special case appears when the first EOF was not yet
   reached, and the DMA channels were prematurely started.

 - Maintainability
   DMA code was a bit obfuscated. Rationalize the code to be
   easily maintainable by anyone.

 - DMA hot chaining
   DMA is not stopped anymore to queue a buffer, the buffer
   is queued with DMA running. As a tribute, a corner case
   exists where chaining happens while DMA finishes the
   chain, and the capture is restarted to deal with the
   missed link buffer.

This patch attemps to address these issues / improvements.

 create mode 100644 Documentation/video4linux/pxa_camera.txt

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
2009-04-06 21:43:45 -03:00
..
2008-10-30 11:38:45 -07:00
2008-08-12 16:07:30 -07:00


What is it?
===========

This is a v4l2/oss device driver for saa7130/33/34/35 based capture / TV
boards.  See http://www.semiconductors.philips.com/pip/saa7134hl for a
description.


Status
======

Almost everything is working.  video, sound, tuner, radio, mpeg ts, ...

As with bttv, card-specific tweaks are needed.  Check CARDLIST for a
list of known TV cards and saa7134-cards.c for the drivers card
configuration info.


Build
=====

Pick up videodev + v4l2 patches from http://bytesex.org/patches/.
Configure, build, install + boot the new kernel.  You'll need at least
these config options:

	CONFIG_I2C=m
	CONFIG_VIDEO_DEV=m

Type "make" to build the driver now.  "make install" installs the
driver.  "modprobe saa7134" should load it.  Depending on the card you
might have to pass card=<nr> as insmod option, check CARDLIST for
valid choices.


Changes / Fixes
===============

Please mail me unified diffs ("diff -u") with your changes, and don't
forget to tell me what it changes / which problem it fixes / whatever
it is good for ...


Known Problems
==============

* The tuner for the flyvideos isn't detected automatically and the
  default might not work for you depending on which version you have.
  There is a tuner= insmod option to override the driver's default.

Card Variations:
================

Cards can use either of these two crystals (xtal):
 - 32.11 MHz -> .audio_clock=0x187de7
 - 24.576MHz -> .audio_clock=0x200000
(xtal * .audio_clock = 51539600)

Some details about 30/34/35:

 - saa7130 - low-price chip, doesn't have mute, that is why all those
 cards should have .mute field defined in their tuner structure.

 - saa7134 - usual chip

 - saa7133/35 - saa7135 is probably a marketing decision, since all those
 chips identifies itself as 33 on pci.

Credits
=======

andrew.stevens@philips.com + werner.leeb@philips.com for providing
saa7134 hardware specs and sample board.


Have fun,

  Gerd

--
Gerd Knorr <kraxel@bytesex.org> [SuSE Labs]