[PATCH] ARM: errata: workaround Cortex-A9 errata 761320 and 794072

[Nitin Garg]

Hi Rob,

Thanks for reply. In that case, I wonder why there is already code which access the diagnostic register. Pls see:
arch/arm/mm/proc-v7.S: __v7_setup
CONFIG_ARM_ERRATA_742230
CONFIG_ARM_ERRATA_742231
CONFIG_ARM_ERRATA_743622
CONFIG_ARM_ERRATA_751472

Regards,
Nitin Garg


-----Original Message-----
From: Rob Herring [mailto:robherring2 at gmail.com] 
Sent: Tuesday, April 01, 2014 8:12 PM
To: Garg Nitin-B37173
Cc: Russell King - ARM Linux; linux-arm-kernel at lists.infradead.org
Subject: Re: [PATCH] ARM: errata: workaround Cortex-A9 errata 761320 and 794072

On Mon, Mar 31, 2014 at 3:34 PM, Nitin Garg <nitin.garg at freescale.com> wrote:
> Add workaround for Cortex-A9 errata 761320 ([present on r0, r1, r2, 
> r3) and 794072 (present on all revisions). These are Category B, 
> present on SMP systems.

These work-arounds don't work on non-secure systems which don't have access to the diagnostic register. There is no architectural way to determine secure vs. non-secure mode. It's been discussed before and decided that these types of work-arounds must go into the bootloader or firmware.

Rob

>
> Signed-off-by: Nitin Garg <nitin.garg at freescale.com>
> ---
>  arch/arm/Kconfig          |   23 +++++++++++++++++++++++
>  arch/arm/mach-imx/Kconfig |    2 ++
>  arch/arm/mm/proc-v7.S     |   11 +++++++++++
>  3 files changed, 36 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 
> a48712e..f8464ff 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1301,6 +1301,29 @@ config ARM_ERRATA_751472
>           operation is received by a CPU before the ICIALLUIS has completed,
>           potentially leading to corrupted entries in the cache or TLB.
>
> +config ARM_ERRATA_794072
> +       bool "ARM errata: A short loop including a DMB instruction might cause a denial of service"
> +       depends on CPU_V7 && SMP
> +       help
> +          This option enables the workaround for the 794072 Cortex-A9
> +          (all revisions). A processor which continuously executes a short
> +          loop containing a DMB instruction might prevent a CP15 operation
> +          broadcast by another processor making further progress, causing
> +          a denial of service. This erratum can be worked around by setting
> +          bit[4] of the undocumented Diagnostic Control Register to 1.
> +
> +config ARM_ERRATA_761320
> +       bool "Full cache line writes to the same memory region from at least two processors might deadlock processor"
> +       depends on CPU_V7 && SMP
> +       help
> +         This option enables the workaround for the 761320 Cortex-A9 (r0..r3).
> +         Under very rare circumstances, full cache line writes
> +         from (at least) 2 processors on cache lines in hazard with
> +         other requests may cause arbitration issues in the SCU,
> +         leading to processor deadlock. This erratum can be
> +         worked around by setting bit[21] of the undocumented
> +         Diagnostic Control Register to 1.
> +
>  config PL310_ERRATA_753970
>         bool "PL310 errata: cache sync operation may be faulty"
>         depends on CACHE_PL310
> diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig 
> index 5740296d..19690c2 100644
> --- a/arch/arm/mach-imx/Kconfig
> +++ b/arch/arm/mach-imx/Kconfig
> @@ -794,6 +794,8 @@ config SOC_IMX6
>  config SOC_IMX6Q
>         bool "i.MX6 Quad/DualLite support"
>         select ARM_ERRATA_764369 if SMP
> +       select ARM_ERRATA_794072 if SMP
> +       select ARM_ERRATA_761320 if SMP
>         select HAVE_ARM_SCU if SMP
>         select HAVE_ARM_TWD if SMP
>         select MIGHT_HAVE_PCI
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S index 
> 195731d..b5e5386 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -337,6 +337,17 @@ __v7_setup:
>         mcrlt   p15, 0, r10, c15, c0, 1         @ write diagnostic register
>  1:
>  #endif
> +#ifdef CONFIG_ARM_ERRATA_794072
> +       mrc     p15, 0, r10, c15, c0, 1         @ read diagnostic register
> +       orr     r10, r10, #1 << 4               @ set bit #4
> +       mcr     p15, 0, r10, c15, c0, 1         @ write diagnostic register
> +#endif
> +#ifdef CONFIG_ARM_ERRATA_761320
> +       cmp     r6, #0x40                       @ present prior to r4p0
> +       mrclt   p15, 0, r10, c15, c0, 1         @ read diagnostic register
> +       orrlt   r10, r10, #1 << 21              @ set bit #21
> +       mcrlt   p15, 0, r10, c15, c0, 1         @ write diagnostic register
> +#endif
>
>         /* Cortex-A15 Errata */
>  3:     ldr     r10, =0x00000c0f                @ Cortex-A15 primary part number
> --
> 1.7.4.1
>
>
>
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