x86: I/O APIC: timer through 8259A second-chance

Some systems incorrectly report the ExtINTA pin of the I/O APIC as the
genuine target of the timer interrupt.  Here is a change that copies timer
pin information found to the other pin if one has been found only.  This
way both a direct and a through-8259A route is tested with the pin letting
these problematic systems work well enough.  If no timer pin information
has been found for the I/O APIC, then local APIC variations are tried
only, similarly to what is done without the change (except without the
misleading messages).

Obviously if we try the first-chance path without being told by the BIOS
to do so, we should not complain either, so do not print the message in
this case.

The 64-bit variation should be updated with a call to
replace_pin_at_irq() which can be done with the upcoming merge.  Since
add_pin_to_irq() is now always called in the first-chance path, the
condition to require it in the second-chance path no longer happens.

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

1 files changed, 28 insertions, 10 deletions

diff --git a/arch/x86/kernel/io_apic_32.c b/arch/x86/kernel/io_apic_32.c
index 63a2f64c765b..a69a59d19e18 100644
--- a/arch/x86/kernel/io_apic_32.c
+++ b/arch/x86/kernel/io_apic_32.c
@@ -2122,6 +2122,7 @@ static inline void __init unlock_ExtINT_logic(void)
 static inline void __init check_timer(void)
 {
         int apic1, pin1, apic2, pin2;
+        int no_pin1 = 0;
         int vector;
         unsigned int ver;
         unsigned long flags;
@@ -2159,10 +2160,30 @@ static inline void __init check_timer(void)
         printk(KERN_INFO "..TIMER: vector=0x%02X apic1=%d pin1=%d apic2=%d pin2=%d\n",
                 vector, apic1, pin1, apic2, pin2);
 
+        /*
+         * Some BIOS writers are clueless and report the ExtINTA
+         * I/O APIC input from the cascaded 8259A as the timer
+         * interrupt input.  So just in case, if only one pin
+         * was found above, try it both directly and through the
+         * 8259A.
+         */
+        if (pin1 == -1) {
+                pin1 = pin2;
+                apic1 = apic2;
+                no_pin1 = 1;
+        } else if (pin2 == -1) {
+                pin2 = pin1;
+                apic2 = apic1;
+        }
+
         if (pin1 != -1) {
                 /*
                  * Ok, does IRQ0 through the IOAPIC work?
                  */
+                if (no_pin1) {
+                        add_pin_to_irq(0, apic1, pin1);
+                        setup_timer_IRQ0_pin(apic1, pin1, vector);
+                }
                 unmask_IO_APIC_irq(0);
                 if (timer_irq_works()) {
                         if (nmi_watchdog == NMI_IO_APIC) {
@@ -2174,26 +2195,23 @@ static inline void __init check_timer(void)
                         goto out;
                 }
                 clear_IO_APIC_pin(apic1, pin1);
-                printk(KERN_ERR "..MP-BIOS bug: 8254 timer not connected to "
-                                "IO-APIC\n");
-        }
+                if (!no_pin1)
+                        printk(KERN_ERR "..MP-BIOS bug: "
+                               "8254 timer not connected to IO-APIC\n");
 
-        printk(KERN_INFO "...trying to set up timer (IRQ0) through the 8259A ... ");
-        if (pin2 != -1) {
+                printk(KERN_INFO "...trying to set up timer (IRQ0) "
+                       "through the 8259A ... ");
                 printk("\n..... (found pin %d) ...", pin2);
                 /*
                  * legacy devices should be connected to IO APIC #0
                  */
+                replace_pin_at_irq(0, apic1, pin1, apic2, pin2);
                 setup_timer_IRQ0_pin(apic2, pin2, vector);
                 unmask_IO_APIC_irq(0);
                 enable_8259A_irq(0);
                 if (timer_irq_works()) {
                         printk("works.\n");
                         timer_through_8259 = 1;
-                        if (pin1 != -1)
-                                replace_pin_at_irq(0, apic1, pin1, apic2, pin2);
-                        else
-                                add_pin_to_irq(0, apic2, pin2);
                         if (nmi_watchdog == NMI_IO_APIC) {
                                 disable_8259A_irq(0);
                                 setup_nmi();
@@ -2206,8 +2224,8 @@ static inline void __init check_timer(void)
                  */
                 disable_8259A_irq(0);
                 clear_IO_APIC_pin(apic2, pin2);
+                printk(" failed.\n");
         }
-        printk(" failed.\n");
 
         if (nmi_watchdog == NMI_IO_APIC) {
                 printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");