From: Sergei Shtylyov <sshtylyov@ru•mvista.com>
To: benh@kernel•crashing.org
Cc: linuxppc-dev@ozlabs•org, paulus@samba•org
Subject: Re: [patch 06/10] 40x decrementer fixes
Date: Sun, 05 Aug 2007 18:19:40 +0400 [thread overview]
Message-ID: <46B5DC7C.70602@ru.mvista.com> (raw)
In-Reply-To: <1186194491.5733.2.camel@gruick>
Benjamin Herrenschmidt wrote:
>>>Allow generic_calibrate_decr to work for 40x platforms. Given that the hardware
>>>behavior is identical, this also changes the set_dec function to reload the PIT
>>>on 40x to match the behavior 44x currently has.
>> Why bother doing this?! This will only warrant you imprecise decrementer
>>interrupts while it should be interrupting at the precise period currently (if
>>you load PIT once)...
> Because that's what the kernel timekeeping code expects ? The reference
> time is the timebase and it doesn't drift.
> The DEC/PIT is commonly used to trigger any timing, such as what is done
> for lost interrupts on some platforms. Also, with dynticks, we'll most
> certainly want variable reload values as well.
That's another matter. :-)
BTW, because of that mere return in set_dec() for the 40x case I had to
write to the PIT myself in the decrementer clockevent's set_next_event()
method -- while for classic PPC I was just calling set_dec(n-1)...
> So I'm very happy to have Josh change the code that way. It makes things
> more consistent accross the board and removes confusion.
Yeah, it's OK now that's my temporary confusion has passed.
Well, it wasn't only not only mine -- the set_dec() code was suggesting
auto-reload mode, and has been obviosuly copied from <asm-ppc/time.h>, so
arch/ppc/ was using the auto-reload mode indeed.
> Ben.
WBR, Sergei
next prev parent reply other threads:[~2007-08-05 14:17 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-03 16:09 [patch 00/10] 4xx patch series for 2.6.24 Josh Boyer
2007-08-03 16:09 ` [patch 01/10] Rename 4xx paths to 40x Josh Boyer
2007-08-03 16:09 ` [patch 02/10] 4xx Kconfig cleanup Josh Boyer
2007-08-04 7:45 ` David Gibson
2007-08-06 12:31 ` Josh Boyer
2007-08-07 3:06 ` David Gibson
2007-08-03 16:09 ` [patch 03/10] Rename 44x bootwrapper Josh Boyer
2007-08-06 4:36 ` David Gibson
2007-08-03 16:09 ` [patch 04/10] 4xx bootwrapper reworks Josh Boyer
2007-08-06 4:38 ` David Gibson
2007-08-06 12:36 ` Josh Boyer
2007-08-07 3:05 ` David Gibson
2007-08-07 13:10 ` Josh Boyer
2007-08-08 1:19 ` David Gibson
2007-08-03 16:09 ` [patch 05/10] 40x MMU Josh Boyer
2007-08-06 4:34 ` David Gibson
2007-08-03 16:09 ` [patch 06/10] 40x decrementer fixes Josh Boyer
2007-08-03 16:47 ` Sergei Shtylyov
2007-08-03 17:10 ` Sergei Shtylyov
2007-08-03 17:25 ` Josh Boyer
2007-08-03 17:30 ` Sergei Shtylyov
2007-08-03 17:30 ` Josh Boyer
2007-08-03 17:35 ` Sergei Shtylyov
2007-08-04 2:28 ` Benjamin Herrenschmidt
2007-08-05 14:12 ` Sergei Shtylyov
2007-08-03 17:15 ` Josh Boyer
2007-08-03 17:25 ` Sergei Shtylyov
2007-08-04 2:28 ` Benjamin Herrenschmidt
2007-08-05 14:19 ` Sergei Shtylyov [this message]
2007-08-03 16:09 ` [patch 07/10] Fix 40x build Josh Boyer
2007-08-06 4:39 ` David Gibson
2007-08-03 16:09 ` [patch 08/10] Bamboo DTS Josh Boyer
2007-08-06 4:53 ` David Gibson
2007-08-06 18:01 ` Jon Loeliger
2007-08-06 18:05 ` Josh Boyer
2007-08-07 13:11 ` Josh Boyer
2007-08-03 16:09 ` [patch 09/10] Bamboo board support Josh Boyer
2007-08-06 4:55 ` David Gibson
2007-08-03 16:09 ` [patch 10/10] Bamboo zImage wrapper Josh Boyer
2007-08-06 5:00 ` David Gibson
2007-08-06 12:39 ` Josh Boyer
2007-08-07 3:04 ` David Gibson
2007-08-07 3:04 ` David Gibson
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