Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=ad62ca2bd89f72e9b80dfaffc463e87bec5e75cb
Commit:     ad62ca2bd89f72e9b80dfaffc463e87bec5e75cb
Parent:     93c9a7ff50a5b39dbdf80129c5da89e6d6256bea
Author:     Thomas Gleixner <[EMAIL PROTECTED]>
AuthorDate: Thu Mar 22 00:11:21 2007 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Mar 22 19:39:05 2007 -0700

    [PATCH] i386: disable local apic timer via command line or dmi quirk
    
    The local APIC timer stops to work in deeper C-States.  This is handled by
    the ACPI code and a broadcast mechanism in the clockevents / tick managment
    code.
    
    Some systems do not expose the deeper C-States to the kernel, but switch
    into deeper C-States behind the kernels back.  This delays the local apic
    timer interrupts for ever and makes the systems unusable.
    
    Add a command line option to disable the local apic timer and a dmi
    quirk for known broken systems.
    
    Andi sayeth:
    
      While not wrong by itself i think it is still better to use some heuristic
      -- like "has battery in ACPI" With the DMI table if the problem is more 
wide
      spread we will just continue extending it.
    
      But anyways should be ok now for .21 although I'm not really happy with
      it.
    
    Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
    Acked-by: Ingo Molnar <[EMAIL PROTECTED]>
    Cc: john stultz <[EMAIL PROTECTED]>
    Grudgingly-acked-by: Andi Kleen <[EMAIL PROTECTED]>
    Cc: Len Brown <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 Documentation/kernel-parameters.txt |    2 +
 arch/i386/kernel/apic.c             |   52 +++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/Documentation/kernel-parameters.txt 
b/Documentation/kernel-parameters.txt
index 856c8b1..06377c7 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1117,6 +1117,8 @@ and is between 256 and 4096 characters. It is defined in 
the file
 
        nolapic         [IA-32,APIC] Do not enable or use the local APIC.
 
+       nolapic_timer   [IA-32,APIC] Do not use the local APIC timer.
+
        noltlbs         [PPC] Do not use large page/tlb entries for kernel
                        lowmem mapping on PPC40x.
 
diff --git a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c
index 5cff797..3682511 100644
--- a/arch/i386/kernel/apic.c
+++ b/arch/i386/kernel/apic.c
@@ -28,6 +28,7 @@
 #include <linux/clockchips.h>
 #include <linux/acpi_pmtmr.h>
 #include <linux/module.h>
+#include <linux/dmi.h>
 
 #include <asm/atomic.h>
 #include <asm/smp.h>
@@ -61,6 +62,8 @@ static int enable_local_apic __initdata = 0;
 
 /* Local APIC timer verification ok */
 static int local_apic_timer_verify_ok;
+/* Disable local APIC timer from the kernel commandline or via dmi quirk */
+static int local_apic_timer_disabled;
 
 /*
  * Debug level, exported for io_apic.c
@@ -266,6 +269,32 @@ static void __devinit setup_APIC_timer(void)
 }
 
 /*
+ * Detect systems with known broken BIOS implementations
+ */
+static int __init lapic_check_broken_bios(struct dmi_system_id *d)
+{
+       printk(KERN_NOTICE "%s detected: disabling lapic timer.\n",
+                      d->ident);
+       local_apic_timer_disabled = 1;
+       return 0;
+}
+
+static struct dmi_system_id __initdata broken_bios_dmi_table[] = {
+       {
+               /*
+                * BIOS exports only C1 state, but uses deeper power
+                * modes behind the kernels back.
+                */
+                 .callback = lapic_check_broken_bios,
+                 .ident = "HP nx6325",
+                 .matches = {
+                       DMI_MATCH(DMI_PRODUCT_NAME, "HP Compaq nx6325"),
+                 },
+        },
+        {}
+};
+
+/*
  * In this functions we calibrate APIC bus clocks to the external timer.
  *
  * We want to do the calibration only once since we want to have local timer
@@ -340,6 +369,22 @@ void __init setup_boot_APIC_clock(void)
        long delta, deltapm;
        int pm_referenced = 0;
 
+       /* Detect know broken systems */
+       dmi_check_system(broken_bios_dmi_table);
+
+       /*
+        * The local apic timer can be disabled via the kernel
+        * commandline or from the dmi quirk above. Register the lapic
+        * timer as a dummy clock event source on SMP systems, so the
+        * broadcast mechanism is used. On UP systems simply ignore it.
+        */
+       if (local_apic_timer_disabled) {
+               /* No broadcast on UP ! */
+               if (num_possible_cpus() > 1)
+                       setup_APIC_timer();
+               return;
+       }
+
        apic_printk(APIC_VERBOSE, "Using local APIC timer interrupts.\n"
                    "calibrating APIC timer ...\n");
 
@@ -1179,6 +1224,13 @@ static int __init parse_nolapic(char *arg)
 }
 early_param("nolapic", parse_nolapic);
 
+static int __init parse_disable_lapic_timer(char *arg)
+{
+       local_apic_timer_disabled = 1;
+       return 0;
+}
+early_param("nolapic_timer", parse_disable_lapic_timer);
+
 static int __init apic_set_verbosity(char *str)
 {
        if (strcmp("debug", str) == 0)
-
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