i386/104678: SMP not working on Turion XP Laptop

[Ariff Abdullah]

The following reply was made to PR i386/104678; it has been noted by GNATS.

From: Ariff Abdullah <ariff at FreeBSD.org>
To: John Baldwin <jhb at FreeBSD.org>
Cc: bug-followup at FreeBSD.org, bde at zeta.org.au, danolson at visi.com,
        rainer.alves at gmail.com, infofarmer at FreeBSD.org
Subject: Re: i386/104678: SMP not working on Turion XP Laptop
Date: Sat, 18 Nov 2006 02:05:27 +0800

 On Fri, 17 Nov 2006 16:50:14 GMT
 John Baldwin <jhb at freebsd.org> wrote:
 >  
 >  Are you using ACPI with Cx hlt states?  It's known that on many
 >  Intel chips at  least, entering C2 or C3 powers off the local APIC
 >  timer.  I know of one  possible workaround that we can use, but
 >  haven't had any time to look at it.   Specifically, we could use
 >  another interrupt source (such as the HPET  counters) and schedule
 >  them to wake us up when the next clock tick should  fire when we
 >  enter C2 or higher sleep state.  You can test this theory by 
 >  setting the sysctl for ACPI to use only C1.
 >  
 Unfortunately, this CPU is a bit special since it support nothing but
 C1. Perhaps the logic is simmilar that is, if the CPU is at it lowest
 Cx states (which in this sense, C1) and HLT is issued, interrupt
 generation within the CPU is simply halted.
 
 On Turion64 X2:
 # sysctl hw.acpi.cpu
 hw.acpi.cpu.cx_supported: C1/0
 hw.acpi.cpu.cx_lowest: C1
 hw.acpi.cpu.cx_usage: 100.00%
 
 On single core Turion64:
 # sysctl hw.acpi.cpu
 hw.acpi.cpu.cx_supported: C1/0 C2/18
 hw.acpi.cpu.cx_lowest: C1
 hw.acpi.cpu.cx_usage: 100.00% 0.00%
 
 Surprisingly, if I deliberately set cx_lowest to C2 on single core
 Turion64 and HLT is issued through idle loop, the simmilar behaviour
 can be observed.
 
 Perhaps the workaround (or fix) best implmented within acpi cpu idle
 hook itself:
 
 acpi_cpu_c1() somewhere within sys/i386/acpica/acpi_machdep.c:
 
 if (at_lowest_cx_states && first_cpu && lapic_timer_enabled) {
 	enable intr;
 } else {
 	issue HLT;
 }
 
 
 This should fix issues with other cpu as well. Resonable? I guess so..
 
 
 
 --
 Ariff Abdullah
 FreeBSD
 
 ... Recording in stereo is obviously too advanced
     and confusing for us idiot ***** users :P ........