Changeset 23291e99 in rtems

Timestamp:

03/26/99 15:42:39 (25 years ago)

Author:

Joel Sherrill <joel.sherrill@…>

Branches:

4.10, 4.11, 4.8, 4.9, 5, master

Children:

39560f1

Parents:

aec5da4

Message:

Patch from Rosimildo DaSilva? <rdasilva@…> and
Emmanuel Raguet <raguet@…> to eliminate a problem
during the boot process on the pc386 BSP. On fast PC's the
calibration routine would hand.

File:

• c/src/lib/libbsp/i386/pc386/timer/timer.c (modified) (3 diffs)

c/src/lib/libbsp/i386/pc386/timer/timer.c

@@ -21 +21 @@
 | This code is base on:
 |   timer.c,v 1.7 1995/12/19 20:07:43 joel Exp - go32 BSP
+|
+| Rosimildo daSilva -ConnectTel, Inc - Fixed infinite loop in the Calibration
+| routine. I've seen this problems with faster machines ( pentiums ). Sometimes
+| RTEMS just hangs at startup.
+|
 | With the following copyright notice:
 | **************************************************************************
@@ -302 +307 @@
 } /* Set_find_average_overhead */
 
-/*-------------------------------------------------------------------------+
-|         Function: Calibrate_loop_1ms
-|      Description: Set loop variable to calibrate a 1ms loop
-| Global Variables: loop1ms
-|        Arguments: none
-|          Returns: Nothing. 
-+--------------------------------------------------------------------------*/
-void
-Calibrate_loop_1ms(void){
-  unsigned int i;
-  unsigned short loadedValue, offset;
-  unsigned int timerValue;
-  rtems_interrupt_level  level;
-  unsigned short lsb, msb;
-  unsigned char status;
-  
-  
-  loop1ms = 100 ;
-  timerValue = 2000;
-  loadedValue = US_TO_TICK(2000);
-  
-  rtems_interrupt_disable(level);
-
-  /*
-   * Compute the offset to apply due to read counter register
-   */
+
+
+/*-------------------------------------------------------------------------+
+| Description: Loads timer 0 with value passed as arguemnt.
+| Returns: Nothing. 
++--------------------------------------------------------------------------*/
+inline void loadTimerValue( unsigned short loadedValue )
+{
   outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
   outport_byte(TIMER_CNTR0, loadedValue >> 0 & 0xff);
   outport_byte(TIMER_CNTR0, loadedValue >> 8 & 0xff);
-
+}
+
+
+/*-------------------------------------------------------------------------+
+| Description: Waits until the counter on timer 0 reaches 0.
+| Returns: Nothing. 
++--------------------------------------------------------------------------*/
+inline void waitTimerStatus( void )
+{
+  unsigned char status;
   outport_byte(TIMER_MODE, CMD_READ_BACK_STATUS); /* read Status counter 0 */
   inport_byte(TIMER_CNTR0, status);
@@ -338 +334 @@
     inport_byte(TIMER_CNTR0, status);
   }
-  
+}
+
+
+/*-------------------------------------------------------------------------+
+| Description: Reads the current value of the timer, and converts the 
+|                          number of ticks to micro-seconds.    
+| Returns: current number of microseconds since last value loaded.. 
++--------------------------------------------------------------------------*/
+inline unsigned short readCurrentTimer()
+{
+  unsigned short lsb, msb;
   outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_LATCH);
   inport_byte(TIMER_CNTR0, lsb);
   inport_byte(TIMER_CNTR0, msb);
-  offset = loadedValue - (unsigned short)((msb << 8) | lsb);
-
-  while (timerValue > 1000){
+  return TICK_TO_US( ( msb << 8 ) | lsb );
+}
+
+
+/*-------------------------------------------------------------------------+
+ * clockbits - Read low order bits of timer 0 (the TOD clock)
+ * This works only for the 8254 chips used in ATs and 386s.
+ *
+ * The timer runs in mode 3 (square wave mode), counting down
+ * by twos, twice for each cycle. So it is necessary to read back the
+ * OUTPUT pin to see which half of the cycle we're in. I.e., the OUTPUT
+ * pin forms the most significant bit of the count. Unfortunately,
+ * the 8253 in the PC/XT lacks a command to read the OUTPUT pin...
+ *
+ * The PC's clock design is soooo brain damaged...
+ *
+ * Rosimildo - I've got this routine from the KA9Q32 distribution and
+ *                         have updated it for the RTEMS environment.
+ +--------------------------------------------------------------------------*/
+unsigned int clockbits(void)
+{
+        int i_state;
+        unsigned int stat,count1, count;
+
+        do 
+        {
+          outport_byte( 0x43, 0xc2 );    /* latch timer 0 count and status for reading */
+          inport_byte( 0x40, stat );     /* get status of timer 0 */
+          inport_byte( 0x40, count1 ); /* lsb of count */
+          inport_byte( 0x40, count ); /* msb of count */
+          count = count1 | ( count << 8 );
+        } while(stat & 0x40);            /* reread if NULL COUNT bit set */
+        stat = (stat & 0x80) << 8;       /* Shift OUTPUT to msb of 16-bit word */
+        if(count == 0)
+                return stat ^ 0x8000;   /* return complement of OUTPUT bit */
+        else
+                return count | stat;    /* Combine OUTPUT with counter */
+}
+
+
+/*-------------------------------------------------------------------------+
+|         Function: Calibrate_loop_1ms
+|      Description: Set loop variable to calibrate a 1ms loop
+| Global Variables: loop1ms
+|        Arguments: none
+|          Returns: Nothing. 
++--------------------------------------------------------------------------*/
+void
+Calibrate_loop_1ms(void)
+{
+  unsigned int i;
+  unsigned short loadedValue, offset;
+  unsigned int timerValue, t1_ref, t2_ref;
+  rtems_interrupt_level  level;
+  unsigned short lsb, msb;
+  unsigned char status;
+  
+
+  printk( "Calibrate_loop_1ms is starting,  please wait ( but not too loooong. )\n" ); 
+ 
+  loop1ms = 200;
+  timerValue = 0;
+
+  /* Let's load the timer with 2ms, initially */
+  loadedValue = US_TO_TICK( 2000 );
+  
+  rtems_interrupt_disable(level);
+  /*
+   * Compute the offset to apply due to read counter register
+   */
+  offset = 0;
+  loadTimerValue( loadedValue + offset );
+  waitTimerStatus();
+  t1_ref = clockbits();
+  offset = loadedValue - readCurrentTimer();
+  while( timerValue < 1000 )
+  {
     loop1ms++;
-
-    /* load timer for 2ms+offset period */
-    outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
-    outport_byte(TIMER_CNTR0, (loadedValue+offset) >> 0 & 0xff);
-    outport_byte(TIMER_CNTR0, (loadedValue+offset) >> 8 & 0xff);
-
-    outport_byte(TIMER_MODE, CMD_READ_BACK_STATUS); /* read Status counter 0 */
-    inport_byte(TIMER_CNTR0, status);
-    while (status & MSK_NULL_COUNT) {   /* wait for counter ready */ 
-      outport_byte(TIMER_MODE, CMD_READ_BACK_STATUS);
-      inport_byte(TIMER_CNTR0, status);
-    }
-    
-    for (i=0; i<loop1ms; i++)
-      outport_byte(SLOW_DOWN_IO, 0);    /* write is # 1us */
-
-    outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_LATCH);
-    inport_byte(TIMER_CNTR0, lsb);
-    inport_byte(TIMER_CNTR0, msb);
-    timerValue = TICK_TO_US((msb << 8) | lsb);
+    loadTimerValue( loadedValue + offset );
+    waitTimerStatus();
+    t1_ref = clockbits();
+    for( i=0; i < loop1ms; i++ )
+       outport_byte( SLOW_DOWN_IO, 0 ); /* write is # 1us */
+    t2_ref = clockbits();
+    timerValue = TICK_TO_US( t1_ref - t2_ref );  /* timer0 is decrementing number of ticks  */
   }
-
+  printk( "Calibrate_loop_1ms timerValue=%d, loop1ms=%d, t1_ref=%x, clockbits=%x, delta=%d\n", 
+                   timerValue, loop1ms, t1_ref, t2_ref, t1_ref - t2_ref );
   rtems_interrupt_enable(level);
 }
+
+
 
 /*-------------------------------------------------------------------------+