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Re: Promblem with PREF (prefetching) in memcpy

To: Carsten Langgaard <>
Subject: Re: Promblem with PREF (prefetching) in memcpy
From: Alan Cox <>
Date: 04 Oct 2002 13:36:08 +0100
Cc: Dominic Sweetman <>, Ralf Baechle <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <>
On Fri, 2002-10-04 at 13:11, Carsten Langgaard wrote:
> Is a bus error exception an address related exception ?
> I'm afraid some implementation think it's not.

So you need an option for broken systems, no new news 8)

> What about an UART RX register, we might loose a character ?
> You can also configure you system, so you get a external interrupt from you
> system controller in case of a bus error, there is no way the CPU can
> relate this interrupt to the prefetching.

The use of memcpy for I/O space isnt permitted in Linux, thats why we
have memcpy_*_io stuff. Thus prefetches should never touch 'special'
spaces. (On x86 the older Athlons corrupt their cache if you do this so
its not a mips specific matter)

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