arch/powerpc/boot/virtex405-head.S has:
#include "ppc_asm.h"
.text
.global _zimage_start
_zimage_start:
/* PPC errata 213: needed by Virtex-4 FX */
mfccr0 0
oris 0,0,[EMAIL PROTECTED]
mtccr0 0
So, this happens first before anything else.
Without this, the boards that I've used crash pretty quickly, so it may be
obvious that the status register is set properly.
As a result, you probably need to do it in the boot loader and not in the
kernel proper.
Steve
-----Original Message-----
From: [EMAIL PROTECTED] on behalf of Darcy Watkins
Sent: Tue 8/26/2008 9:01 AM
To: linuxppc-embedded
Subject: PPC405EP errata CPU 213 (Incorrect data may be flushed from thedata
cache)
Hello,
The IBM/AMCC errata document recommends setting reserved bits 1 & 3 in
CCR0 as a workaround to PPC405EP errata CPU 213 (Incorrect data may be
flushed from the data cache). For a start, I just tried hacking in a
few lines of assembly code into...
arch/powerpc/kernel/head_40x.S
---
Around line #839 ...
bl early_init /* We have to do this with MMU on */
/*
* Decide what sort of machine this is and initialize the MMU.
*/
mr r3,r31
mr r4,r30
mr r5,r29
mr r6,r28
mr r7,r27
bl machine_init
bl MMU_init
/* DLW hack!! - for PPC405EP errata CPU 213 */
mfspr r4,SPRN_CCR0
oris r4,r4,0x5000
mtspr SPRN_CCR0,r4
isync
/* Go back to running unmapped so we can load up new values
* and change to using our exception vectors.
* On the 4xx, all we have to do is invalidate the TLB to clear
* the old 16M byte TLB mappings.
*/
lis r4,[EMAIL PROTECTED]
...
Since I am not a PowerPC assembler guru, does this appear right?
I think that eventually I'd want to create a cpu_setup_40x.S with the
fixup code as part of a setup_cpu_405ep function and then hook this into
cputable.c, but first I want to make sure that the errata workaround is
actually taking effect (and also not being undone by later startup
code).
--
Regards,
Darcy
--------------
Darcy L. Watkins - Senior Software Developer
Tranzeo Wireless Technologies, Inc.
19273 Fraser Way, Pitt Meadows, BC, Canada V3Y 2V4
T:604-460-6002 ext:410
http://www.tranzeo.com
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