On Jan 25, 2011, at 12:02 AM, Liu Yu wrote:
> This errata 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....@freescale.com>
> ---
> This is an erratum workaround patch.
> It would be better if the patch can go into 2.6.38.
>
> arch/powerpc/include/asm/reg.h | 2 +
> arch/powerpc/math-emu/math_efp.c | 53 +++++++++++++++++++++++++++++++++++++-
> 2 files changed, 54 insertions(+), 1 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
> index 6315edc..0abfd91 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -833,6 +833,8 @@
> #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
> diff --git a/arch/powerpc/math-emu/math_efp.c
> b/arch/powerpc/math-emu/math_efp.c
> index 41f4ef3..634830b 100644
> --- a/arch/powerpc/math-emu/math_efp.c
> +++ b/arch/powerpc/math-emu/math_efp.c
> @@ -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....@freescale.com>
> * Yu Liu, <yu....@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
> + */
This isn't the way to do this. We normally add entries in cputable.c an add a
new cpu_feature_bit for the errata.
Than above we'd do:
if (cur_cpu_spec->cpu_features & CPU_FTR_E500_A005_ERRATUM)
> + 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);
> --
> 1.6.4
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
