linux-mips
[Top] [All Lists]

[PATCH] Timing with TOY on Au1100

To: Linux MIPS <linux-mips@linux-mips.org>
Subject: [PATCH] Timing with TOY on Au1100
From: Rodolfo Giometti <giometti@linux.it>
Date: Wed, 29 Mar 2006 17:37:48 +0200
Organization: GNU/Linux Device Drivers, Embedded Systems and Courses
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.11+cvs20060126
I've checked the TOY programming on a board Au1100 based and I notice
that the frequency is not correct. Infact the TOY frequency is just
HZ/2... I suggest this patch that should fix this topic. 

The patch also try to fix (in a poor manner) a problem related with
the jiffie_drift and the fact that HZ may be in the range [100:1000].

The last block (@@ -189,15 +196,11 @@) remove a bug during system wake
up when HZ is 1000. The while() may loose too much time computing the
last_match20 parameter and if TOY must run at 1K the system hangs
since the TOY is programmed with an alredy passed time stamp.

Ciao,

Rodolfo

Index: common/time.c
===================================================================
RCS file: 
/home/develop/cvs_private/linux-mips-exadron/arch/mips/au1000/common/time.c,v
retrieving revision 1.3
diff -u -r1.3 time.c
--- a/common/time.c     26 Jul 2005 21:33:32 -0000      1.3
+++ b/common/time.c     29 Mar 2006 15:26:03 -0000
@@ -142,7 +143,7 @@
                time_elapsed = pc0 - last_match20;
        }
 
-       while (time_elapsed > 0) {
+       do {
                do_timer(regs);
 #ifndef CONFIG_SMP
                update_process_times(user_mode(regs));
@@ -150,14 +151,19 @@
                time_elapsed -= MATCH20_INC;
                last_match20 += MATCH20_INC;
                jiffie_drift++;
-       }
+       } while (time_elapsed > MATCH20_INC);
 
        last_pc0 = pc0;
        au_writel(last_match20 + MATCH20_INC, SYS_TOYMATCH2);
        au_sync();
 
-       /* our counter ticks at 10.009765625 ms/tick, we we're running
-        * almost 10uS too slow per tick.
+#if HZ < 400
+       /* our counter ticks at 
+        *   HZ =  100 -> 10.009765625    ms/tick
+        *   HZ =  400 ->  2.50244140625  ms/tick
+        *   HZ =  500 ->  1.983642578125 ms/tick
+        *   HZ = 1000 ->  0.9765625      ms/tick
+        * so HZ = 400 may be a good discriminating point...
         */
 
        if (jiffie_drift >= 999) {
@@ -167,6 +173,7 @@
                update_process_times(user_mode(regs));
 #endif
        }
+#endif
 
        return IRQ_HANDLED;
 }
@@ -189,15 +196,11 @@
                time_elapsed = pc0 - last_match20;
        }
 
-       while (time_elapsed > 0) {
-               time_elapsed -= MATCH20_INC;
-               last_match20 += MATCH20_INC;
-       }
+       last_match20 += time_elapsed - time_elapsed%MATCH20_INC;
 
        last_pc0 = pc0;
        au_writel(last_match20 + MATCH20_INC, SYS_TOYMATCH2);
        au_sync();
-
 }
 
 /* This is just for debugging to set the timer for a sleep delay.

-- 

GNU/Linux Solutions                  e-mail:    giometti@enneenne.com
Linux Device Driver                             giometti@gnudd.com
Embedded Systems                                giometti@linux.it
UNIX programming                     phone:     +39 349 2432127

<Prev in Thread] Current Thread [Next in Thread>
  • [PATCH] Timing with TOY on Au1100, Rodolfo Giometti <=