x86: I/O APIC: AEOI timer acknowledgement clean-ups

The code that used to be in do_slow_gettimeoffset() that relied on the
IRR bit of the master 8259A PIC for IRQ0 to check the state of the output
timer 0 of the PIT is no longer there.  As a result, there is no need to
use the POLL command to acknowledge the timer interrupt in the "8259A
Virtual Wire", except for the NMI watchdog when the i82489DX APIC is used
(this is because this particular APIC treats NMIs as level-triggered and
keeping the input asserted would keep motherboard NMI sources held off for
too long).  Remove the unneeded bits and adjust comments accordingly.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/io_apic_32.c b/arch/x86/kernel/io_apic_32.c
index a40d54fc1fdd819125a1d7b609566180062b6ecc..c64b3f5cc121e5f5385e721c993fb1979cc48766 100644 (file)
--- a/arch/x86/kernel/io_apic_32.c
+++ b/arch/x86/kernel/io_apic_32.c
@@ -2146,19 +2146,17 @@ static inline void __init check_timer(void)
        set_intr_gate(vector, interrupt[0]);
 
        /*
-        * Subtle, code in do_timer_interrupt() expects an AEOI
-        * 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
-        * timer_interrupt() and for the i82489DX when using
-        * the NMI watchdog.
+        * As IRQ0 is to be enabled in the 8259A, the virtual
+        * wire has to be disabled in the local APIC.  Also
+        * timer interrupts need to be acknowledged manually in
+        * the 8259A for the i82489DX when using the NMI
+        * watchdog as that APIC treats NMIs as level-triggered.
+        * The AEOI mode will finish them in the 8259A
+        * automatically.
         */
        apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
        init_8259A(1);
-       timer_ack = !cpu_has_tsc;
-       timer_ack |= (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
+       timer_ack = (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
        if (timer_over_8254 > 0)
                enable_8259A_irq(0);
 
@@ -2219,6 +2217,7 @@ static inline void __init check_timer(void)
                printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");
                nmi_watchdog = 0;
        }
+       timer_ack = 0;
 
        printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");
 
@@ -2237,7 +2236,6 @@ static inline void __init check_timer(void)
 
        printk(KERN_INFO "...trying to set up timer as ExtINT IRQ...");
 
-       timer_ack = 0;
        init_8259A(0);
        make_8259A_irq(0);
        apic_write_around(APIC_LVT0, APIC_DM_EXTINT);

diff --git a/arch/x86/kernel/io_apic_64.c b/arch/x86/kernel/io_apic_64.c
index ef1a8dfcc529a36643bdbe34f835eb1819c5f265..7c34e38e42197e58782a0d791453377723dafee0 100644 (file)
--- a/arch/x86/kernel/io_apic_64.c
+++ b/arch/x86/kernel/io_apic_64.c
@@ -1669,11 +1669,8 @@ static inline void __init check_timer(void)
        assign_irq_vector(0, TARGET_CPUS);
 
        /*
-        * Subtle, code in do_timer_interrupt() expects an AEOI
-        * 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.
+        * As IRQ0 is to be enabled in the 8259A, the virtual
+        * wire has to be disabled in the local APIC.
         */
        apic_write(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
        init_8259A(1);

diff --git a/arch/x86/kernel/nmi_32.c b/arch/x86/kernel/nmi_32.c
index 11b14bbaa61e6be6cfb1ffe7fd5b4c8f69fd71a7..d322901c38e6ef1989eebccd55dec01243f40bb9 100644 (file)
--- a/arch/x86/kernel/nmi_32.c
+++ b/arch/x86/kernel/nmi_32.c
@@ -131,7 +131,7 @@ int __init check_nmi_watchdog(void)
        kfree(prev_nmi_count);
        return 0;
 error:
-       timer_ack = !cpu_has_tsc;
+       timer_ack = 0;
 
        return -1;
 }

diff --git a/arch/x86/kernel/time_32.c b/arch/x86/kernel/time_32.c
index 2ff21f398934b049975a427e463b046e9226d079..5f29f12da50ce24624a5b3878029d4a11c2379b0 100644 (file)
--- a/arch/x86/kernel/time_32.c
+++ b/arch/x86/kernel/time_32.c
@@ -84,8 +84,7 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
        if (timer_ack) {
                /*
                 * Subtle, when I/O APICs are used we have to ack timer IRQ
-                * manually to reset the IRR bit for do_slow_gettimeoffset().
-                * This will also deassert NMI lines for the watchdog if run
+                * manually to deassert NMI lines for the watchdog if run
                 * on an 82489DX-based system.
                 */
                spin_lock(&i8259A_lock);