[ltp] ALSA sound driver for CS4236+ working

[linux-thinkpad@www.bm-soft.com]

Michael,

You're right -- the key to get sound working on the PCI crystal chips is to
disable  PCI-bus power management. We just learned that ourselves -- you
beat me to the post by about 4 hours.

On machines that use the Pheonix BIOS (such as the new A20 and T20 models),
you can disable PCI-bus power management using the BIOS setup program. On
other systems, I guess you would need the PS2 utility.

What happens with PCI-bus power management enabled is that the lack of
activity on the PCI bus causes the chip to suspend PCI clocks, causing the
Crystal chip to not function when you try to use it later. The Windows
Crystal drivers apparently patch the crystal DSP code to circumvent the
problem, but that code is not in the ALSA drivers. I am trying to get
details about the patch that I can pass on to the ALSA folks for inclusion
in a future ALSA release.

The impact of disabling PCI-bus power management (specifically, the PCI
CLKRUN protocol) is that battery life is reduced. One estimate I was given
was a reduction of about 20 minutes, but I haven't actually done the
comparison to confirm that.

-- Keith

Keith Frechette
Linux Development Lead, Mobile Computing Options and Software Development
IBM Research Triangle Park, North Carolina
kfrechet@us.ibm.com / 919-543-3761 / TieLine:441-3761


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Subject:        [ltp] ALSA sound driver for CS4236+ working



I'm listening to some mp3's playing on xmms 0.9.something on a 600x with
the latest 0.5.x alsa drivers installed at the moment. Joy!

The only thing beyond the normal alsa configuration that I needed to do
was to turn off the PCI-bus power management feature, using the ps2
control program (or the windows thinkpad configuration utiility) and
comment out the early load of the sound modules as suggested by Mr. Hood
(Thanks). So far, so good. I haven't tried any of the suspend or
unplugged operation features yet with the driver enabled, however.

Let me emphasize that: you *must* turn of the PCI-bus power management
feature. I couldn't get anything to work at all untill I did that, and
there was no indication of progress either.

I notice that the sound subsystem in the 600x is PCI, as is the usb
device, irda port, and the PCMCIA controller. This should go a long way
toward relieving the resource starvation problems.

Now if i could just get the usb and irda ports working..... ;-)

Thomas Hood wrote:
>
> wolfie wrote:
> >
> > What about the CS461x chip? is this working with the new ALSA release?
>
> I don't know whether or not it's working (since the
> ThinkPad 600 doesn't have a CS461x) but the latest
> ALSA release does include a driver for the CS461x.
>
> Thomas
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--

--Michael

"The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all progress
depends on the unreasonable man."
                         - George Bernard Shaw
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