Re: Managing Power for PCI Audio Device Driver
Re: Managing Power for PCI Audio Device Driver
- Subject: Re: Managing Power for PCI Audio Device Driver
- From: Mark Cookson <email@hidden>
- Date: Mon, 30 Sep 2002 16:16:15 -0700
On Monday, September 30, 2002, at 03:30 PM, Michel wrote:
On Monday 30 September 2002 23:12, Mark Cookson wrote:
AppleOnboardAudio implements setPowerState(), as does the
AppleUSBTrinityAudioDevice object in AppleUSBAudio.
As a subsidiary question, what is the major difference between a warm
(reboot) boot and a cold (shutdown + power up) in term of power
states? In my
case my device works fine after a cold boot OR after a wakup from
sleep, but
it's silent after a plain 'restart'. The card appears to be in perfect
state
as far as the controler goes, the DMA works, all is fine save there is
no
sound.
That seems perfectly illogical to me, really ;-)
Any idea?
There is no difference to the OS between a warm boot (restart) and a
cold boot (power on) as Open Firmware configures the built in hardware
the same way no matter if it's a warm boot or a cold boot. There is a
difference to the hardware, however. In my case, Open Firmware
initializes the built in hardware for me, so it looks the same every
time the computer boots. However, PCI devices aren't powered down
across a reboot, they might get a reset signal, but probably not much
more. Your initHardware() routine might have to check the state of
your hardware and do a conditional initialization depending on how the
card is already configured.
If your card works fine after a wake from sleep, are you implementing
setPowerState()? If so, your initHardware() routine should probably
call the same wake-up function that your setPowerState() function calls.
--
Mark Cookson
Engineering Droid
Apple Computer, Inc.
Core Audio CPU Software
6 Infinite Loop MS 306-2CW
Cupertino, CA 95014
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