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powerpc/85xx: Workaroudn e500 CPU erratum A005 

This erratum can occur if a single-precision floating-point,
double-precision floating-point or vector floating-point instruction on a
mispredicted branch path signals one of the floating-point data interrupts
which are enabled by the SPEFSCR (FINVE, FDBZE, FUNFE or FOVFE bits).  This
interrupt must be recorded in a one-cycle window when the misprediction is
resolved.  If this extremely rare event should occur, the result could be:

The SPE Data Exception from the mispredicted path may be reported
erroneously if a single-precision floating-point, double-precision
floating-point or vector floating-point instruction is the second
instruction on the correct branch path.

According to errata description, some efp instructions which are not
supposed to trigger SPE exceptions can trigger the exceptions in this case.
However, as we haven't emulated these instructions here, a signal will
send to userspace, and userspace application would exit.

This patch re-issue the efp instruction that we haven't emulated,
so that hardware can properly execute it again if this case happen.

Signed-off-by: Liu Yu <yu.liu@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
This commit is contained in:
Liu Yu 2011-01-25 14:02:13 +08:00 committed by Kumar Gala
parent f4154e160a
commit ac6f120369
2 changed files with 54 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/include/asm/reg.h
View File

@ -862,6 +862,8 @@
#define PVR_7450 0x80000000
#define PVR_8540 0x80200000
#define PVR_8560 0x80200000
#define PVR_VER_E500V1 0x8020
#define PVR_VER_E500V2 0x8021
/*
* For the 8xx processors, all of them report the same PVR family for
* the PowerPC core. The various versions of these processors must be

53
arch/powerpc/math-emu/math_efp.c
View File

@ -1,7 +1,7 @@
/*
* arch/powerpc/math-emu/math_efp.c
*
* Copyright (C) 2006-2008 Freescale Semiconductor, Inc. All rights reserved.
* Copyright (C) 2006-2008, 2010 Freescale Semiconductor, Inc.
*
* Author: Ebony Zhu, <ebony.zhu@freescale.com>
* Yu Liu, <yu.liu@freescale.com>
@ -104,6 +104,8 @@
#define FP_EX_MASK (FP_EX_INEXACT | FP_EX_INVALID | FP_EX_DIVZERO | \
FP_EX_UNDERFLOW | FP_EX_OVERFLOW)
static int have_e500_cpu_a005_erratum;
union dw_union {
u64 dp[1];
u32 wp[2];
@ -652,6 +654,15 @@ update_regs:
return 0;
illegal:
if (have_e500_cpu_a005_erratum) {
/* according to e500 cpu a005 erratum, reissue efp inst */
regs->nip -= 4;
#ifdef DEBUG
printk(KERN_DEBUG "re-issue efp inst: %08lx\n", speinsn);
#endif
return 0;
}
printk(KERN_ERR "\nOoops! IEEE-754 compliance handler encountered un-supported instruction.\ninst code: %08lx\n", speinsn);
return -ENOSYS;
}
@ -718,3 +729,43 @@ int speround_handler(struct pt_regs *regs)
return 0;
}
int __init spe_mathemu_init(void)
{
u32 pvr, maj, min;
pvr = mfspr(SPRN_PVR);
if ((PVR_VER(pvr) == PVR_VER_E500V1) ||
(PVR_VER(pvr) == PVR_VER_E500V2)) {
maj = PVR_MAJ(pvr);
min = PVR_MIN(pvr);
/*
* E500 revision below 1.1, 2.3, 3.1, 4.1, 5.1
* need cpu a005 errata workaround
*/
switch (maj) {
case 1:
if (min < 1)
have_e500_cpu_a005_erratum = 1;
break;
case 2:
if (min < 3)
have_e500_cpu_a005_erratum = 1;
break;
case 3:
case 4:
case 5:
if (min < 1)
have_e500_cpu_a005_erratum = 1;
break;
default:
break;
}
}
return 0;
}
module_init(spe_mathemu_init);