[Timers] Initialise timers on first use

Timers are sometimes required before the call to initialise(), so we
cannot rely on initialise() to set up the timers before use.

Also fix a potential integer overflow issue in generic_currticks_udelay()

diff --git a/src/core/timer.c b/src/core/timer.c
index ef80c04..4e047ea 100644 (file)
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -20,7 +20,6 @@
 
 #include <stddef.h>
 #include <assert.h>
-#include <gpxe/init.h>
 #include <gpxe/timer.h>
 
 static struct timer ts_table[0]
@@ -28,34 +27,39 @@ static struct timer ts_table[0]
 static struct timer ts_table_end[0]
        __table_end ( struct timer, timers );
 
-
-static struct timer *used_ts = NULL;
-
 /*
  * This function may be used in custom timer driver.
  *
  * This udelay implementation works well if you've got a
  * fast currticks().
  */
-void generic_currticks_udelay(unsigned int usecs)
-{
-       tick_t t;
-
-       t = currticks();
-       while (t + usecs > currticks())
-               ; /* xxx: Relax the cpu some way. */
+void generic_currticks_udelay ( unsigned int usecs ) {
+       tick_t start;
+       tick_t elapsed;
+       
+       start = currticks();
+       do {
+               /* xxx: Relax the cpu some way. */
+               elapsed = ( currticks() - start );
+       } while ( elapsed < usecs );
 }
 
+/**
+ * Identify timer source
+ *
+ * @ret timer          Timer source
+ */
+static struct timer * timer ( void ) {
+       static struct timer *ts = NULL;
 
-static void timer_init(void)
-{
-       struct timer *ts;
+       /* If we have a timer, use it */
+       if ( ts )
+               return ts;
 
-       for (ts = ts_table; ts < ts_table_end; ts++) {
-               if ( ts->init() == 0 ) {
-                       used_ts = ts;
-                       return;
-               }
+       /* Scan for a usable timer */
+       for ( ts = ts_table ; ts < ts_table_end ; ts++ ) {
+               if ( ts->init() == 0 )
+                       return ts;
        }
 
        /* No timer found; we cannot continue */
@@ -63,10 +67,6 @@ static void timer_init(void)
        while ( 1 ) {};
 }
 
-struct init_fn ts_init_fn __init_fn ( INIT_NORMAL ) = {
-       .initialise = timer_init,
-};
-
 /**
  * Read current time
  *
@@ -74,9 +74,8 @@ struct init_fn ts_init_fn __init_fn ( INIT_NORMAL ) = {
  */
 tick_t currticks ( void ) {
        tick_t ct;
-       assert(used_ts);
 
-       ct = used_ts->currticks();
+       ct = timer()->currticks();
        DBG ( "currticks: %ld.%06ld seconds\n",
              ct / USECS_IN_SEC, ct % USECS_IN_SEC );
 
@@ -89,8 +88,7 @@ tick_t currticks ( void ) {
  * @v usecs    Time to delay, in microseconds
  */
 void udelay ( unsigned int usecs ) {
-       assert(used_ts);
-       used_ts->udelay ( usecs );
+       timer()->udelay ( usecs );
 }
 
 /**

diff --git a/src/include/gpxe/timer.h b/src/include/gpxe/timer.h
index ecd3000..b705722 100644 (file)
--- a/src/include/gpxe/timer.h
+++ b/src/include/gpxe/timer.h
@@ -2,6 +2,7 @@
 #define GPXE_TIMER_H
 
 #include <stddef.h>
+#include <gpxe/tables.h>
 
 typedef unsigned long tick_t;