From: dianders@google.com (Doug Anderson)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: mm: Add workaround for erratum 763126
Date: Thu, 8 May 2014 09:57:03 -0700 [thread overview]
Message-ID: <CAD=FV=XeYdgqk3-CpS2NNXFAnn+uGDC6844d-L6vfS=SYEuw-Q@mail.gmail.com> (raw)
In-Reply-To: <1399528508-2806-1-git-send-email-arjun.kv@samsung.com>
Arjun,
Thanks for sending this.
On Wed, May 7, 2014 at 10:55 PM, Arjun.K.V <arjun.kv@samsung.com> wrote:
> From: "Arjun.K.V" <arjun.kv@samsung.com>
>
> Three processor exclusive access livelock.
> In a system with three or more coherent masters that all use
> the ldrex/strex synchronization primitives to access a semaphore
> in coherent cacheable memory, there is a possibility of a
> livelock condition where two masters continuously attempt
> and fail to get the lock while the third master
> continuously reads the lock.
>
> Workaround is to set the "Snoop-delayed exclusive handling"
> bit in the Auxiliary Control Register, ACTLR[31] to 1.
> This hardware is installed in each processor to detect
> that the load/store exclusive livelock scenario may be occurring
> and delay snoops for a period of time to allow the load
> exclusive/store exclusive loop to complete and make
> forward progress.
>
> Change-Id: Idcf066e25ea6571a0f5da6f3a770318c1a9d6fff
> Signed-off-by: Arjun.K.V <arjun.kv@samsung.com>
> ---
> arch/arm/Kconfig | 13 +++++++++++++
> arch/arm/mm/proc-v7.S | 43 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 56 insertions(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index db3c541..80b8562 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1464,6 +1464,19 @@ source "drivers/pci/pcie/Kconfig"
>
> source "drivers/pcmcia/Kconfig"
>
> +config ARM_ERRATA_763126
> + bool "ARM errata: Three processor exclusive access livelock"
> + depends on CPU_V7 && SMP
> + help
> + This enables the workaround got ARM Erratum 763126.
> + In a system with three or more coherent masters that all use the
> + ldrex/strex synchronization primitives to access a semaphore in
> + coherent cacheable memory, there is a possibility of a livelock
> + condition where two masters continuously attempt and fail to get
> + the lock while the third master continuously reads the lock.
> + Workaround is to set the "Snoop-delayed exclusive handling" bit
> + in the Auxiliary Control Register, ACTLR[31] to 1.
> +
> endmenu
>
> menu "Kernel Features"
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 195731d..e6d22c7 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -136,6 +136,29 @@ ENTRY(cpu_v7_do_resume)
> mcr p15, 0, r7, c2, c0, 1 @ TTB 1
> #endif
> mcr p15, 0, r11, c2, c0, 2 @ TTB control register
> +
> +#ifdef CONFIG_ARM_ERRATA_763126
> + mrc p15, 0, r0, c0, c0, 0 @ Check if we are A15s
> + ubfx r1, r0, #4, #12
> + ldr r2, =0x00000c0f
> + teq r1, r2
> + bne 6f
> + and r1, r0, #0x00f00000
> + and r2, r0, #0x0000000f
> + orr r2, r2, r1, lsr #20-4
> + cmp r2, #0x20 @ Is the revision < r2p0
As I mentioned locally, I think this affects all A15s equally.
Specifically, I see that:
* this affects r0p4
* this affects r2p0, r2p1, r2p2, r2p3, r2p4
* this affects r3p0, r3p1, r3p2, r3p3
* this affects r4p0
Just get rid of the revision test and assume that on all A15s (w/ 3 or
more processors) you need this.
-Doug
next prev parent reply other threads:[~2014-05-08 16:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-08 5:55 [PATCH] ARM: mm: Add workaround for erratum 763126 Arjun.K.V
2014-05-08 16:57 ` Doug Anderson [this message]
2014-05-08 17:38 ` Will Deacon
2014-05-08 17:57 ` Doug Anderson
2014-05-08 18:05 ` Will Deacon
[not found] ` <CAFY15YHPSLMh6iA1PQHjsneL_Kxarc0xL5uJ7_px71cbmJbrgQ@mail.gmail.com>
2014-05-09 14:44 ` Catalin Marinas
2014-05-12 16:36 ` Doug Anderson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAD=FV=XeYdgqk3-CpS2NNXFAnn+uGDC6844d-L6vfS=SYEuw-Q@mail.gmail.com' \
--to=dianders@google.com \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.