x86: apic - rearrange functions and comments

Rearrange functions and comments to find differences
easier.

Also use apic_printk in setup_boot_APIC_clock for
64bit mode.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 38 insertions, 10 deletions

diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index 13dea935b4eb..46523c0cc6f6 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -81,6 +81,9 @@ static void lapic_timer_setup(enum clock_event_mode mode,
 static void lapic_timer_broadcast(cpumask_t mask);
 static void apic_pm_activate(void);
 
+/*
+ * The local apic timer can be used for any function which is CPU local.
+ */
 static struct clock_event_device lapic_clockevent = {
         .name           = "lapic",
         .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT
@@ -127,6 +130,11 @@ static int modern_apic(void)
         return lapic_get_version() >= 0x14;
 }
 
+/*
+ * Paravirt kernels also might be using these below ops. So we still
+ * use generic apic_read()/apic_write(), which might be pointing to different
+ * ops in PARAVIRT case.
+ */
 void xapic_wait_icr_idle(void)
 {
         while (apic_read(APIC_ICR) & APIC_ICR_BUSY)
@@ -175,7 +183,6 @@ static struct apic_ops xapic_ops = {
 };
 
 struct apic_ops __read_mostly *apic_ops = &xapic_ops;
-
 EXPORT_SYMBOL_GPL(apic_ops);
 
 static void x2apic_wait_icr_idle(void)
@@ -244,6 +251,10 @@ int lapic_get_maxlvt(void)
         return APIC_INTEGRATED(GET_APIC_VERSION(v)) ? GET_APIC_MAXLVT(v) : 2;
 }
 
+/*
+ * Local APIC timer
+ */
+
 /* Clock divisor is set to 1 */
 #define APIC_DIVISOR 1
 
@@ -257,7 +268,6 @@ int lapic_get_maxlvt(void)
  * We do reads before writes even if unnecessary, to get around the
  * P5 APIC double write bug.
  */
-
 static void __setup_APIC_LVTT(unsigned int clocks, int oneshot, int irqen)
 {
         unsigned int lvtt_value, tmp_value;
@@ -474,10 +484,10 @@ static int __init calibrate_APIC_clock(void)
 void __init setup_boot_APIC_clock(void)
 {
         /*
-         * The local apic timer can be disabled via the kernel commandline.
-         * 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.
+         * The local apic timer can be disabled via the kernel
+         * commandline or from the CPU detection code. 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 (disable_apic_timer) {
                 printk(KERN_INFO "Disabling APIC timer\n");
@@ -489,7 +499,9 @@ void __init setup_boot_APIC_clock(void)
                 return;
         }
 
-        printk(KERN_INFO "Using local APIC timer interrupts.\n");
+        apic_printk(APIC_VERBOSE, "Using local APIC timer interrupts.\n"
+                    "calibrating APIC timer ...\n");
+
         if (calibrate_APIC_clock()) {
                 /* No broadcast on UP ! */
                 if (num_possible_cpus() > 1)
@@ -508,6 +520,7 @@ void __init setup_boot_APIC_clock(void)
                 printk(KERN_WARNING "APIC timer registered as dummy,"
                         " due to nmi_watchdog=%d!\n", nmi_watchdog);
 
+        /* Setup the lapic or request the broadcast */
         setup_APIC_timer();
 }
 
@@ -577,6 +590,7 @@ void smp_apic_timer_interrupt(struct pt_regs *regs)
         irq_enter();
         local_apic_timer_interrupt();
         irq_exit();
+
         set_irq_regs(old_regs);
 }
 
@@ -1248,6 +1262,13 @@ void __init connect_bsp_APIC(void)
         enable_apic_mode();
 }
 
+/**
+ * disconnect_bsp_APIC - detach the APIC from the interrupt system
+ * @virt_wire_setup:    indicates, whether virtual wire mode is selected
+ *
+ * Virtual wire mode is necessary to deliver legacy interrupts even when the
+ * APIC is disabled.
+ */
 void disconnect_bsp_APIC(int virt_wire_setup)
 {
         /* Go back to Virtual Wire compatibility mode */
@@ -1347,9 +1368,11 @@ int hard_smp_processor_id(void)
 #ifdef CONFIG_PM
 
 static struct {
-        /* 'active' is true if the local APIC was enabled by us and
-           not the BIOS; this signifies that we are also responsible
-           for disabling it before entering apm/acpi suspend */
+        /*
+         * 'active' is true if the local APIC was enabled by us and
+         * not the BIOS; this signifies that we are also responsible
+         * for disabling it before entering apm/acpi suspend
+         */
         int active;
         /* r/w apic fields */
         unsigned int apic_id;
@@ -1458,6 +1481,11 @@ static int lapic_resume(struct sys_device *dev)
         return 0;
 }
 
+/*
+ * This device has no shutdown method - fully functioning local APICs
+ * are needed on every CPU up until machine_halt/restart/poweroff.
+ */
+
 static struct sysdev_class lapic_sysclass = {
         .name           = "lapic",
         .resume         = lapic_resume,