linux/sound
Ben Gardiner 52e2c5d38e ASoC: davinci-pcm: convert to BATCH mode
The davinci-pcm driver's snd_pcm_ops pointer function currently calls into
the edma controller driver to read the current positions of the edma channels
to determine pos to return to the ALSA framework. In particular,
davinci_pcm_pointer() calls edma_get_position() and the latter has a comment
indicating that "Its channel should not be active when this is called" whereas
the channel is surely active when snd_pcm_ops.pointer is called.

The operation of davinci-pcm in capture and playback appears to follow close
the other pcm drivers who export SNDRV_PCM_INFO_BATCH except that davinci-pcm
does not report it's positions from pointer() using the last transferred
chunk. Instead it peeks directly into the edma controller to determine the
current position as discussed above.

Convert the davinci-pcm driver to BATCH mode: count the periods elapsed in the
prtd->period member and use its value to report the 'pos' to the alsa
framework in the davinci_pcm_pointer function.

There is a phase offset of 2 periods between the position used by dma setup
and the position reported in the pointer function. Either +2 in the dma
setup or -2 in the pointer function (with wrapping, both) accounts for this
offset -- I opted for the latter since it makes the first-time setup clearer.

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Reviewed-by: Steven Faludi <stevenfaludi@nanometrics.ca>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
2011-05-25 19:14:31 +08:00
..
aoa Fix common misspellings 2011-03-31 11:26:23 -03:00
arm Merge branch 'for-2.6.39' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound-2.6 into for-2.6.39 2011-04-03 19:28:29 +09:00
atmel ALSA: fix invalid hardware.h include in ac97c for AVR32 architecture 2011-01-25 18:07:10 +01:00
core Merge branch 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6 2011-04-07 11:14:49 -07:00
drivers Fix common misspellings 2011-03-31 11:26:23 -03:00
firewire ALSA: firewire-speakers: fix hang when unplugging a running device 2011-03-30 08:56:57 +02:00
i2c sound: don't use flush_scheduled_work() 2010-12-13 09:22:44 +01:00
isa Fix common misspellings 2011-03-31 11:26:23 -03:00
mips
oss Fix common misspellings 2011-03-31 11:26:23 -03:00
parisc
pci Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 2011-04-10 09:56:10 -07:00
pcmcia ALSA: use linux/io.h to fix compile warnings 2011-02-02 17:49:53 +01:00
ppc Fix common misspellings 2011-03-31 11:26:23 -03:00
sh sound: sh: ctrl_in/outX to __raw_read/writeX conversion. 2010-10-27 15:53:50 +09:00
soc ASoC: davinci-pcm: convert to BATCH mode 2011-05-25 19:14:31 +08:00
sparc dt/sound: Eliminate users of of_platform_{,un}register_driver 2011-02-28 13:22:44 -07:00
spi ALSA: AT73C213: Rectify misleading comment. 2010-11-11 02:03:29 +01:00
synth
usb Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 2011-04-10 09:56:10 -07:00
ac97_bus.c sound: Fixed line limit issue in sound/ac97_bus.c 2010-12-06 16:09:49 +01:00
Kconfig ALSA: add LaCie FireWire Speakers/Griffin FireWave Surround driver 2011-03-15 08:42:22 +01:00
last.c
Makefile ALSA: add LaCie FireWire Speakers/Griffin FireWave Surround driver 2011-03-15 08:42:22 +01:00
sound_core.c sound: Use sound_register_*() for additional OSS minor devices 2011-03-09 20:10:37 +01:00
sound_firmware.c sound: read i_size with i_size_read() 2011-03-18 15:14:57 +01:00