idle Athlon with IOAPIC is 10C warmer since 2.6.3-bk1

[Thomas Schlichter <thomas.schlichter@web.de>]

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Hi,

a few days ago I noticed that my Athlon 3000+ was relatively hot (49C) 
although it was completely idle. At that time I was running 2.6.3-mm3 with 
ACPI and IOAPIC-support enabled.

As I tried 2.6.3, the idle temperature was at normal 39C. So I did do some 
binary search with the -bk patches and found the patch that causes the high 
idle temperature. It is ChangeSet@1.1626 aka 8259-timer-ack-fix.patch.

A patch to revert that ChangeSet for 2.6.4-rc1-mm2 is attached.

Best regards
   Thomas Schlichter

P.S.: The high idle temperature only shows if the  IOAPIC is used.
P.P.S: I already sent this mail last saturday, but as it seems to have never 
reached LKML I send it again. I'm sorry if you got it twice!

[-- Attachment #2: revert-8259-timer-ack-fix.patch --]
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--- linux-2.6.4-rc1-mm2/arch/i386/kernel/io_apic.c.orig	2004-03-03 14:56:10.000000000 +0100
+++ linux-2.6.4-rc1-mm2/arch/i386/kernel/io_apic.c	2004-03-03 17:35:03.000000000 +0100
@@ -2157,10 +2157,6 @@ static inline void check_timer(void)
 {
 	int pin1, pin2;
 	int vector;
-	unsigned int ver;
-
-	ver = apic_read(APIC_LVR);
-	ver = GET_APIC_VERSION(ver);
 
 	/*
 	 * get/set the timer IRQ vector:
@@ -2174,17 +2170,11 @@ static inline void check_timer(void)
 	 * mode for the 8259A whenever interrupts are routed
 	 * through I/O APICs.  Also IRQ0 has to be enabled in
 	 * the 8259A which implies the virtual wire has to be
-	 * disabled in the local APIC.  Finally timer interrupts
-	 * need to be acknowledged manually in the 8259A for
-	 * do_slow_timeoffset() and for the i82489DX when using
-	 * the NMI watchdog.
+	 * disabled in the local APIC.
 	 */
 	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
 	init_8259A(1);
-	if (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver))
-		timer_ack = 1;
-	else
-		timer_ack = !cpu_has_tsc;
+	timer_ack = 1;
 	enable_8259A_irq(0);
 
 	pin1 = find_isa_irq_pin(0, mp_INT);
@@ -2202,8 +2192,7 @@ static inline void check_timer(void)
 				disable_8259A_irq(0);
 				setup_nmi();
 				enable_8259A_irq(0);
-				if (check_nmi_watchdog() < 0);
-					timer_ack = !cpu_has_tsc;
+				check_nmi_watchdog();
 			}
 			return;
 		}
@@ -2226,8 +2215,7 @@ static inline void check_timer(void)
 				add_pin_to_irq(0, 0, pin2);
 			if (nmi_watchdog == NMI_IO_APIC) {
 				setup_nmi();
-				if (check_nmi_watchdog() < 0);
-					timer_ack = !cpu_has_tsc;
+				check_nmi_watchdog();
 			}
 			return;
 		}