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[CPUFREQ] Longhaul - Workaround issues with APIC. 

There is no need to worry about local APIC.
There is need to worry about I/O APIC, because I/O APIC
is replacing good old 8259. According to Nehemiah datasheet VIA is
using 3-wire bus to connect local APIC to I/O APIC.

"[...] When IA32_APIC_BASE[11] is set to 0, processor APICs based on the 3-wire APIC
 bus cannot be generally re-enabled until a system hardware reset. The 3-wire bus
 looses track of arbitration that would be necessary for complete re-enabling. Certain
 (local) APIC functionality can be enabled. [...]"

So we must set disable bit for each interrupt in I/O APIC registers.
Same situation as for PIC - we must poke registers direcly.
How to do this? I don't know. So at the moment it is better to fail.

Signed-off-by: Rafa³ Bilski <rafalbilski@interia.pl>
Signed-off-by: Dave Jones <davej@redhat.com>
hifive-unleashed-5.1
Rafa³ Bilski 2006-07-04 17:50:57 +02:00 committed by Dave Jones
parent dadb49d874
commit 48b7bde0f6
1 changed files with 12 additions and 0 deletions
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12
arch/i386/kernel/cpu/cpufreq/longhaul.c
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@ -688,6 +688,18 @@ static int __init longhaul_init(void)
if (c->x86_vendor != X86_VENDOR_CENTAUR || c->x86 != 6)
return -ENODEV;
#ifdef CONFIG_SMP
if (num_online_cpus() > 1) {
return -ENODEV;
printk(KERN_ERR PFX "More than 1 CPU detected, longhaul disabled.\n");
}
#endif
#ifdef CONFIG_X86_IO_APIC
if (cpu_has_apic) {
printk(KERN_ERR PFX "APIC detected. Longhaul is currently broken in this configuration.\n");
return -ENODEV;
}
#endif
switch (c->x86_model) {
case 6 ... 9:
return cpufreq_register_driver(&longhaul_driver);