Re: 2.4.22 APM problems with IBM Thinkpad's

[Mikael Pettersson]

Ruben Puettmann writes:
 > On Wed, Aug 13, 2003 at 03:13:02PM +0200, Mikael Pettersson wrote:
 > > 
 > > This sounds like a well-known APM/local-APIC clash.
 > 
 > nice to know ... 
 > > 
 > > Never ever use DISPLAY_BLANK if you also have SMP or UP_APIC.
 > 
 > not nice so ;-( how is it with acpi? Same problem?
 > 
 > > With APIC support enabled (SMP or UP_APIC), APM must be constrained:
 > > DISPLAY_BLANK off
 > > CPU_IDLE off
 > > built-in driver, not module
 > 
 > Why will this not be disabled in make *config so that nobody will run in
 > this problem?
 > 
 > > This is because the apm driver does BIOS calls, and many BIOSen
 > > (including the code in graphics cards, e.g. all Radeons it seems)
 > > like to hang if a local APIC timer interrupt arrives.

Several reasons:
- The interaction wasn't understood initially, and some problems
  didn't start appearing until late last year. The problems are
  also system & configuration dependent.
  Case in point #1: my P3B-F and P4T-E ASUS mainboards never had
  problems until they started running 2.5 kernels, where HZ==1000
  greatly increased the likelihood of a local APIC timer interrupt
  while in BIOS screen blanking code.
  Case in point #2: my TUSL2-C ASUS mobo (RIP) worked great until
  I switched from a Millenium to a Radeon 8500, and found that it
  hung because of local APIC timer interrupts while in BIOS screen
  blanking code, even in 2.4 kernels.
- Fixing the APM driver would require that someone who understands
  it modifies it to avoid BIOS calls (other than suspend/resume) when
  UP_APIC is active. I'm not that person.
- The problems can be worked around by avoiding misconfigurations.
-
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