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From: "H. Peter Anvin" <hpa@zytor.com>
To: cpufreq@www.linux.org.uk, davej@codemonkey.org.uk, linux@brodo.de
Subject: Fix for longrun.c for degenerate case
Date: Fri, 07 May 2004 19:06:49 -0700	[thread overview]
Message-ID: <409C40B9.6000603@zytor.com> (raw)

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Hi all,

I ran into a system the other day which had a Transmeta processor, but 
configured in a degenerate, fixed-frequency configuration.  It crashed 
booting Fedora Core 2 test 3 due to a division by zero in the longrun 
cpufreq driver.  The attached patch fixes this.

	-hpa

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Index: linux-2.5/arch/i386/kernel/cpu/cpufreq/longrun.c
===================================================================
RCS file: /home/hpa/kernel/bkcvs/linux-2.5/arch/i386/kernel/cpu/cpufreq/longrun.c,v
retrieving revision 1.19
diff -u -r1.19 longrun.c
--- linux-2.5/arch/i386/kernel/cpu/cpufreq/longrun.c	13 Apr 2004 15:52:00 -0000	1.19
+++ linux-2.5/arch/i386/kernel/cpu/cpufreq/longrun.c	6 May 2004 05:32:50 -0000
@@ -46,11 +46,16 @@
 	rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
 	msr_lo &= 0x0000007F;
 	msr_hi &= 0x0000007F;
-
-	policy->min = longrun_low_freq + msr_lo * 
-		((longrun_high_freq - longrun_low_freq) / 100);
-	policy->max = longrun_low_freq + msr_hi * 
-		((longrun_high_freq - longrun_low_freq) / 100);
+	
+	if ( longrun_high_freq <= longrun_low_freq ) {
+		/* Assume degenerate Longrun table */
+		policy->min = policy->max = longrun_high_freq;
+	} else {
+		policy->min = longrun_low_freq + msr_lo * 
+			((longrun_high_freq - longrun_low_freq) / 100);
+		policy->max = longrun_low_freq + msr_hi * 
+			((longrun_high_freq - longrun_low_freq) / 100);
+	}
 	policy->cpu = 0;
 }
 
@@ -70,10 +75,15 @@
 	if (!policy)
 		return -EINVAL;
 
-	pctg_lo = (policy->min - longrun_low_freq) / 
-		((longrun_high_freq - longrun_low_freq) / 100);
-	pctg_hi = (policy->max - longrun_low_freq) / 
-		((longrun_high_freq - longrun_low_freq) / 100);
+	if ( longrun_high_freq <= longrun_low_freq ) {
+		/* Assume degenerate Longrun table */
+		pctg_lo = pctg_hi = 100;
+	} else {
+		pctg_lo = (policy->min - longrun_low_freq) / 
+			((longrun_high_freq - longrun_low_freq) / 100);
+		pctg_hi = (policy->max - longrun_low_freq) / 
+			((longrun_high_freq - longrun_low_freq) / 100);
+	}
 
 	if (pctg_hi > 100)
 		pctg_hi = 100;

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             reply	other threads:[~2004-05-08  2:06 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-08  2:06 H. Peter Anvin [this message]
2004-05-09 14:16 ` Fix for longrun.c for degenerate case Dominik Brodowski

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