x86: Allow platforms to force enable apic

Some embedded x86 platforms don't setup the APIC in the
BIOS/bootloader and would be forced to add "lapic" on the kernel
command line. That's a bit akward.

Split out the force enable code from detect_init_APIC() and allow
platform code to call it from the platform setup. That avoids the
command line parameter and possible replication of the MSR dance in
the force enable code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <1287510389-8388-1-git-send-email-dirk.brandewie@gmail.com>
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>

1 files changed, 54 insertions, 33 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 850657d1b0ed..463839645f9b 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1531,13 +1531,60 @@ static int __init detect_init_APIC(void)
         return 0;
 }
 #else
+
+static int apic_verify(void)
+{
+        u32 features, h, l;
+
+        /*
+         * The APIC feature bit should now be enabled
+         * in `cpuid'
+         */
+        features = cpuid_edx(1);
+        if (!(features & (1 << X86_FEATURE_APIC))) {
+                pr_warning("Could not enable APIC!\n");
+                return -1;
+        }
+        set_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);
+        mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;
+
+        /* The BIOS may have set up the APIC at some other address */
+        rdmsr(MSR_IA32_APICBASE, l, h);
+        if (l & MSR_IA32_APICBASE_ENABLE)
+                mp_lapic_addr = l & MSR_IA32_APICBASE_BASE;
+
+        pr_info("Found and enabled local APIC!\n");
+        return 0;
+}
+
+int apic_force_enable(void)
+{
+        u32 h, l;
+
+        if (disable_apic)
+                return -1;
+
+        /*
+         * Some BIOSes disable the local APIC in the APIC_BASE
+         * MSR. This can only be done in software for Intel P6 or later
+         * and AMD K7 (Model > 1) or later.
+         */
+        rdmsr(MSR_IA32_APICBASE, l, h);
+        if (!(l & MSR_IA32_APICBASE_ENABLE)) {
+                pr_info("Local APIC disabled by BIOS -- reenabling.\n");
+                l &= ~MSR_IA32_APICBASE_BASE;
+                l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;
+                wrmsr(MSR_IA32_APICBASE, l, h);
+                enabled_via_apicbase = 1;
+        }
+        return apic_verify();
+}
+
 /*
  * Detect and initialize APIC
  */
 static int __init detect_init_APIC(void)
 {
-        u32 h, l, features;
-
         /* Disabled by kernel option? */
         if (disable_apic)
                 return -1;
@@ -1567,38 +1614,12 @@ static int __init detect_init_APIC(void)
                                 "you can enable it with \"lapic\"\n");
                         return -1;
                 }
-                /*
-                 * Some BIOSes disable the local APIC in the APIC_BASE
-                 * MSR. This can only be done in software for Intel P6 or later
-                 * and AMD K7 (Model > 1) or later.
-                 */
-                rdmsr(MSR_IA32_APICBASE, l, h);
-                if (!(l & MSR_IA32_APICBASE_ENABLE)) {
-                        pr_info("Local APIC disabled by BIOS -- reenabling.\n");
-                        l &= ~MSR_IA32_APICBASE_BASE;
-                        l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;
-                        wrmsr(MSR_IA32_APICBASE, l, h);
-                        enabled_via_apicbase = 1;
-                }
-        }
-        /*
-         * The APIC feature bit should now be enabled
-         * in `cpuid'
-         */
-        features = cpuid_edx(1);
-        if (!(features & (1 << X86_FEATURE_APIC))) {
-                pr_warning("Could not enable APIC!\n");
-                return -1;
+                if (apic_force_enable())
+                        return -1;
+        } else {
+                if (apic_verify())
+                        return -1;
         }
-        set_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);
-        mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;
-
-        /* The BIOS may have set up the APIC at some other address */
-        rdmsr(MSR_IA32_APICBASE, l, h);
-        if (l & MSR_IA32_APICBASE_ENABLE)
-                mp_lapic_addr = l & MSR_IA32_APICBASE_BASE;
-
-        pr_info("Found and enabled local APIC!\n");
 
         apic_pm_activate();