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Re: [PATCH] x86: use explicit timing delay for pit accesses in kernel and pcspkr driver

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From: Rene Herman
Subject: Re: [PATCH] x86: use explicit timing delay for pit accesses in kernel and pcspkr driver
Date: Monday, February 18, 2008 - 2:04 pm

On 18-02-08 21:43, H. Peter Anvin wrote:


I mean that before the linux kernel used a port 0x80 write as an I/O delay 
it used a short jump (two in a row actually...) as such and this was at the 
time that it actually ran on the old legacy stuff that is of most concern here.

No, if I'm not mistaken, those two jumps are actually what the udelay() is 
going to do anyway as part of delay_loop() at that early stage so that even 
before loops_per_jiffy calibration, I believe we should still be okay.

Yes, it's a bit of a "well, hrrm" thing, but, well... loops_per_jiffy can be 
initialised a bit more conservatively then today as well (and as discussed 
earlier, possibly per CPU family) but I believe it's actually sort of fine 
not too worry much about it...

Rene.
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Messages in current thread:
[PATCH] x86: use explicit timing delay for pit accesses in ..., David P. Reed, (Mon Feb 18, 11:58 am)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Alan Cox, (Mon Feb 18, 1:17 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Mon Feb 18, 1:38 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., H. Peter Anvin, (Mon Feb 18, 1:43 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Mon Feb 18, 2:04 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Mon Feb 18, 2:05 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., H. Peter Anvin, (Mon Feb 18, 2:44 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Mon Feb 18, 2:59 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., H. Peter Anvin, (Mon Feb 18, 3:01 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Mon Feb 18, 3:07 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Mon Feb 18, 3:32 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., H. Peter Anvin, (Mon Feb 18, 3:43 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., H. Peter Anvin, (Mon Feb 18, 3:44 pm)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Ingo Molnar, (Tue Feb 19, 2:46 am)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Wed Feb 20, 5:06 am)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., H. Peter Anvin, (Wed Feb 20, 10:05 am)
Re: [PATCH] x86: use explicit timing delay for pit accesse ..., Rene Herman, (Wed Feb 20, 10:09 am)
Re: [linux-kernel] Re: [PATCH] x86: use explicit timing de ..., David P. Reed, (Wed Feb 20, 1:13 pm)
Re: [linux-kernel] Re: [PATCH] x86: use explicit timing de ..., Rene Herman, (Wed Feb 20, 11:21 pm)