
Documentation for the Cirrus Logic/Crystal SoundFusion cs46xx/cs4280 audio 
controller chips (2001/05/11)

The cs46xx audio driver supports the DSP line of Cirrus controllers. 
Specifically, the cs4610, cs4612, cs4614, cs4622, cs4624, cs4630 and the cs4280
products.  This driver uses the generic ac97_codec driver for AC97 codec
support.  


Features:

Full Duplex Playback/Capture supported from 8k-48k.
16Bit Signed LE & 8Bit Unsigned, with Mono or Stereo supported.

APM/PM - 2.2.x PM is enabled and functional. APM can also
be enabled for 2.4.x by modifying the CS46XX_ACPI_SUPPORT macro
definition.

DMA playback buffer size is configurable from 16k (defaultorder=2) up to 2Meg 
(defaultorder=11).  DMA capture buffer size is fixed at a single 4k page as
two 2k fragments.

MMAP seems to work well with QuakeIII, and test XMMS plugin.

Myth2 works, but the polling logic is not fully correct, but is functional.

The 2.4.4-ac6 gameport code in the cs461x joystick driver has been tested 
with a Microsoft Sidewinder joystick (cs461x.o and sidewinder.o).  This 
audio driver must be loaded prior to the joystick driver to enable the
DSP task image supporting the joystick device.


Limitations:

SPDIF is currently not supported.

Primary codec support only.  No secondary codec support is implemented.



NOTES:

Hercules Game Theatre XP - the EGPIO2 pin controls the external Amp,
and has been tested.
Module parameter hercules_egpio_disable set to 1, will force a 0 to EGPIODR
to disable the external amplifier.

VTB Santa Cruz - the GPIO7/GPIO8 on the Secondary Codec control
the external amplifier for the "back" speakers, since we do not
support the secondary codec then this external amp is not
turned on.  The primary codec external amplifier is supported but
note that the AC97 EAPD bit is inverted logic (amp_voyetra()).

DMA buffer size - there are issues with many of the Linux applications
concerning the optimal buffer size.  Several applications request a 
certain fragment size and number and then do not verify that the driver
has the ability to support the requested configuration.  
SNDCTL_DSP_SETFRAGMENT ioctl is used to request a fragment size and
number of fragments.  Some applications exit if an error is returned
on this particular ioctl. Therefore, in alignment with the other OSS audio 
drivers, no error is returned when a SETFRAGs IOCTL is received, but the 
values passed from the app are not used in any buffer calculation 
(ossfragshift/ossmaxfrags are not used).
Use the "defaultorder=N" module parameter to change the buffer size if
you have an application that requires a specific number of fragments
or a specific buffer size (see below).

Debug Interface
---------------
There is an ioctl debug interface to allow runtime modification of the 
debug print levels.  This debug interface code can be disabled from the 
compilation process with commenting the following define:
#define CSDEBUG_INTERFACE 1
There is also a debug print methodolgy to select printf statements from
different areas of the driver.  A debug print level is also used to allow
additional printfs to be active.  Comment out the following line in the
driver to disable compilation of the CS_DBGOUT print statements:
#define CSDEBUG 1
 
Please see the definitions for cs_debuglevel and cs_debugmask for additional
information on the debug levels and sections.

There is also a csdbg executable to allow runtime manipulation of these 
parameters.  for a copy email: twoller@crystal.cirrus.com



MODULE_PARMS definitions
------------------------
module_param(defaultorder, ulong, 0);
defaultorder=N
where N is a value from 1 to 12
The buffer order determines the size of the dma buffer for the driver.
under Linux, a smaller buffer allows more responsiveness from many of the 
applications (e.g. games).  A larger buffer allows some of the apps (esound) 
to not underrun the dma buffer as easily.  As default, use 32k (order=3)
rather than 64k as some of the games work more responsively.
(2^N) * PAGE_SIZE = allocated buffer size

module_param(cs_debuglevel, ulong, 0644);
module_param(cs_debugmask, ulong, 0644);
cs_debuglevel=N
cs_debugmask=0xMMMMMMMM
where N is a value from 0 (no debug printfs), to 9 (maximum)
0xMMMMMMMM is a debug mask corresponding to the CS_xxx bits (see driver source).

module_param(hercules_egpio_disable, ulong, 0);
hercules_egpio_disable=N
where N is a 0 (enable egpio), or a 1 (disable egpio support)

module_param(initdelay, ulong, 0);
initdelay=N
This value is used to determine the millescond delay during the initialization
code prior to powering up the PLL.  On laptops this value can be used to
assist with errors on resume, mostly with IBM laptops.  Basically, if the 
system is booted under battery power then the mdelay()/udelay() functions fail to 
properly delay the required time.  Also, if the system is booted under AC power
and then the power removed, the mdelay()/udelay() functions will not delay properly.
 
module_param(powerdown, ulong, 0);
powerdown=N
where N is 0 (disable any powerdown of the internal blocks) or 1 (enable powerdown)


module_param(external_amp, bool, 0);
external_amp=1
if N is set to 1, then force enabling the EAPD support in the primary AC97 codec.
override the detection logic and force the external amp bit in the AC97 0x26 register
to be reset (0).  EAPD should be 0 for powerup, and 1 for powerdown.  The VTB Santa Cruz
card has inverted logic, so there is a special function for these cards.

module_param(thinkpad, bool, 0);
thinkpad=1
if N is set to 1, then force enabling the clkrun functionality.
Currently, when the part is being used, then clkrun is disabled for the entire system,
but re-enabled when the driver is released or there is no outstanding open count.

