Patch set updated for coreboot: b996367 x86: use car_(get|set)_var accessors for apic timer

[Aaron Durbin]

Aaron Durbin ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/5411

-gerrit

commit b996367619d892e913f61cffaab2d80810d23d51
Author: Aaron Durbin 
Date:   Fri Mar 28 08:40:59 2014 -0500

x86: use car_(get|set)_var accessors for apic timer

The timer_fsb variable was not correctly being accessed in the
    presence of cache-as-ram. The cache-as-ram backing store could
    be torn down but then udelay() could be called causing hangs from
    accessing variables that have unknown values.

Instead change the timer_fsb variable to g_timer_fsb and obtain
    the value through a local access method that does the correct things
    to obtain the correct value.

Change-Id: Ia3e30808498cbe4a7f6f116c17a8cf1240a807a3
    Signed-off-by: Aaron Durbin 
---
 src/cpu/x86/lapic/apic_timer.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/cpu/x86/lapic/apic_timer.c b/src/cpu/x86/lapic/apic_timer.c
index 868fb92..8700584 100644
--- a/src/cpu/x86/lapic/apic_timer.c
+++ b/src/cpu/x86/lapic/apic_timer.c
@@ -34,14 +34,14 @@
  */

#if CONFIG_UDELAY_LAPIC_FIXED_FSB
-static const u32 timer_fsb = CONFIG_UDELAY_LAPIC_FIXED_FSB;
+static const u32 g_timer_fsb = CONFIG_UDELAY_LAPIC_FIXED_FSB;

static int set_timer_fsb(void)
 {
    return 0;
 }
 #else
-static u32 timer_fsb CAR_GLOBAL = 0;
+static u32 g_timer_fsb CAR_GLOBAL;

static int set_timer_fsb(void)
 {
@@ -56,20 +56,20 @@ static int set_timer_fsb(void)
    switch (c.x86_model) {
    case 0xe:  /* Core Solo/Duo */
    case 0x1c: /* Atom */
-		timer_fsb = core_fsb[rdmsr(MSR_FSB_FREQ).lo & 7];
+		car_set_var(g_timer_fsb, core_fsb[rdmsr(MSR_FSB_FREQ).lo & 7]);
    	break;
    case 0xf:  /* Core 2 or Xeon */
    case 0x17: /* Enhanced Core */
-		timer_fsb = core2_fsb[rdmsr(MSR_FSB_FREQ).lo & 7];
+		car_set_var(g_timer_fsb, core2_fsb[rdmsr(MSR_FSB_FREQ).lo & 7]);
    	break;
    case 0x2a: /* SandyBridge BCLK fixed at 100MHz*/
    case 0x3a: /* IvyBridge BCLK fixed at 100MHz*/
    case 0x3c: /* Haswell BCLK fixed at 100MHz */
    case 0x45: /* Haswell-ULT BCLK fixed at 100MHz */
-		timer_fsb = 100;
+		car_set_var(g_timer_fsb, 100);
    	break;
    default:
-		timer_fsb = 200;
+		car_set_var(g_timer_fsb, 200);
    	break;
    }

@@ -77,6 +77,11 @@ static int set_timer_fsb(void)
 }
 #endif

+static inline u32 get_timer_fsb(void)
+{
+	return car_get_var(g_timer_fsb);
+}
+
 void init_timer(void)
 {
    /* Set the apic timer to no interrupts and periodic mode */
@@ -94,15 +99,18 @@ void init_timer(void)

void udelay(u32 usecs)
 {
-	u32 start, value, ticks;
+	u32 start, value, ticks, timer_fsb;

if (!thread_yield_microseconds(usecs))
    	return;

+	timer_fsb = get_timer_fsb();
    if (!timer_fsb || (lapic_read(LAPIC_LVTT) &
    	(LAPIC_LVT_TIMER_PERIODIC | LAPIC_LVT_MASKED)) !=
-		(LAPIC_LVT_TIMER_PERIODIC | LAPIC_LVT_MASKED))
+		(LAPIC_LVT_TIMER_PERIODIC | LAPIC_LVT_MASKED)) {
    	init_timer();
+		timer_fsb = get_timer_fsb();
+	}

/* Calculate the number of ticks to run, our FSB runs at timer_fsb Mhz */
    ticks = usecs * timer_fsb;
@@ -125,9 +133,11 @@ void timer_monotonic_get(struct mono_time *mt)
 {
    uint32_t current_tick;
    uint32_t usecs_elapsed;
+	uint32_t timer_fsb;

if (!mono_counter.initialized) {
    	init_timer();
+		timer_fsb = get_timer_fsb();
    	/* An FSB frequency of 200Mhz provides a 20 second polling
    	 * interval between timer_monotonic_get() calls before wrap
    	 * around occurs. */
@@ -139,6 +149,7 @@ void timer_monotonic_get(struct mono_time *mt)
    	mono_counter.initialized = 1;
    }

+	timer_fsb = get_timer_fsb();
    current_tick = lapic_read(LAPIC_TMCCT);
    /* Note that the APIC timer counts down. */
    usecs_elapsed = (mono_counter.last_value - current_tick) / timer_fsb;