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[MIPS] R4000/R4400 errata workarounds

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This is the gereric part of R4000/R4400 errata workarounds.  They include 
compiler and assembler support as well as some source code modifications 
to address the problems with some combinations of multiply/divide+shift 
instructions as well as the daddi and daddiu instructions.

 Changes included are as follows:

1. New Kconfig options to select workarounds by platforms as necessary.

2. Arch top-level Makefile to pass necessary options to the compiler; also 
   incompatible configurations are detected (-mno-sym32 unsupported as 
   horribly intrusive for little gain).

3. Bug detection updated and shuffled -- the multiply/divide+shift problem 
   is lethal enough that if not worked around it makes the kernel crash in 
   time_init() because of a division by zero; the daddiu erratum might 
   also trigger early potentially, though I have not observed it.  On the 
   other hand the daddi detection code requires the exception subsystem to 
   have been initialised (and is there mainly for information).

4. r4k_daddiu_bug() added so that the existence of the erratum can be 
   queried by code at the run time as necessary; useful for generated code 
   like TLB fault and copy/clear page handlers.

5. __udelay() updated as it uses multiplication in inline assembly.

 Note that -mdaddi requires modified toolchain (which has been maintained 
by myself and available from my site for ~4years now -- versions covered 
are GCC 2.95.4 - 4.1.2 and binutils from 2.13 onwards).  The -mfix-r4000 
and -mfix-r4400 have been standard for a while though.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Maciej W. Rozycki
2007-10-23 12:43:11 +01:00
committed by Ralf Baechle
parent 2b22c034d0
commit 20d60d9973
7 changed files with 148 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/asm-mips/delay.h
+10 -2
View File
@@ -6,13 +6,16 @@
* Copyright (C) 1994 by Waldorf Electronics
* Copyright (C) 1995 - 2000, 01, 03 by Ralf Baechle
* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
* Copyright (C) 2007 Maciej W. Rozycki
*/
#ifndef _ASM_DELAY_H
#define _ASM_DELAY_H
#include <linux/param.h>
#include <linux/smp.h>
#include <asm/compiler.h>
#include <asm/war.h>
static inline void __delay(unsigned long loops)
{
@@ -50,7 +53,7 @@ static inline void __delay(unsigned long loops)
static inline void __udelay(unsigned long usecs, unsigned long lpj)
{
unsigned long lo;
unsigned long hi, lo;
/*
* The rates of 128 is rounded wrongly by the catchall case
@@ -70,11 +73,16 @@ static inline void __udelay(unsigned long usecs, unsigned long lpj)
: "=h" (usecs), "=l" (lo)
: "r" (usecs), "r" (lpj)
: GCC_REG_ACCUM);
else if (sizeof(long) == 8)
else if (sizeof(long) == 8 && !R4000_WAR)
__asm__("dmultu\t%2, %3"
: "=h" (usecs), "=l" (lo)
: "r" (usecs), "r" (lpj)
: GCC_REG_ACCUM);
else if (sizeof(long) == 8 && R4000_WAR)
__asm__("dmultu\t%3, %4\n\tmfhi\t%0"
: "=r" (usecs), "=h" (hi), "=l" (lo)
: "r" (usecs), "r" (lpj)
: GCC_REG_ACCUM);
__delay(usecs);
}