From: Sergei Shtylyov <sshtylyov@ru•mvista.com>
To: Kumar Gala <galak@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org, Paul Mackerras <paulus@samba•org>
Subject: Re: [POWERPC] Fix off-by-one error in setting decrementer on Book E
Date: Tue, 30 Oct 2007 17:23:42 +0300 [thread overview]
Message-ID: <47273E6E.4030103@ru.mvista.com> (raw)
In-Reply-To: <42A23BAB-6081-41CC-870C-7C7F094D69C3@kernel.crashing.org>
Hello.
Kumar Gala wrote:
>>The decrementer in Book E and 4xx processors interrupts on the
>>transition from 1 to 0, rather than on the 0 to -1 transition as on
>>64-bit server and 32-bit "classic" (6xx/7xx/7xxx) processors.
>>This fixes the problem by making set_dec subtract 1 from the count for
>>server and classic processors. Since set_dec already had a bunch of
>>ifdefs to handle different processor types, there is no net increase
>>in ugliness. :)
>>This also removes a redundant call to set the decrementer to
>>0x7fffffff - it was already set to that earlier in timer_interrupt.
>>Signed-off-by: Paul Mackerras <paulus@samba•org>
>>---
> ...
>>diff --git a/include/asm-powerpc/time.h b/include/asm-powerpc/time.h
>>index f058955..eed64bd 100644
>>--- a/include/asm-powerpc/time.h
>>+++ b/include/asm-powerpc/time.h
>>@@ -183,6 +183,7 @@ static inline void set_dec(int val)
>> #elif defined(CONFIG_8xx_CPU6)
>> set_dec_cpu6(val);
>> #else
>>+ --val; /* classic decrementer interrupts when dec goes negative */
>> #ifdef CONFIG_PPC_ISERIES
>> int cur_dec;
> Unless I'm reading set_dec() you are getting --val on booke.
You meant "misreading"?
Indeed the patch is decrementing count for *both* book E and classic CPUs
now, and that slipped past my attention the first time. The patch summary
("Fix off-by-one error in setting decrementer on Book E") also looks stange --
there is *no* off-by-one error on Book E, and the description correctly says
that we're fixing off-by-one on classic/server CPUs.
Maybe I should even go and post my patch variant instead...
WBR, Sergei
prev parent reply other threads:[~2007-10-30 14:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-29 2:57 [POWERPC] Fix off-by-one error in setting decrementer on Book E Paul Mackerras
2007-10-29 3:10 ` Paul Mackerras
2007-10-29 3:16 ` Olof Johansson
2007-10-29 16:52 ` Sergei Shtylyov
2007-10-31 9:40 ` Paul Mackerras
2007-10-31 14:12 ` Sergei Shtylyov
2007-10-30 3:52 ` Kumar Gala
2007-10-30 14:23 ` Sergei Shtylyov [this message]
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