[PATCH] ARM: mm: enable L1 prefetch on Cortex-A9

From: robherring2@gmail.com (Rob Herring)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: mm: enable L1 prefetch on Cortex-A9
Date: Tue, 16 Jun 2015 08:47:33 -0500	[thread overview]
Message-ID: <CAL_JsqKTC+BO6bin3Qekjn37Np6F86Uvv1-194VGTyYxcNfjHw@mail.gmail.com> (raw)
In-Reply-To: <1434023550-20147-1-git-send-email-thomas.petazzoni@free-electrons.com>

On Thu, Jun 11, 2015 at 6:52 AM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> The Cortex-A9 has a L1 prefetch capability documented at
> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0388e/Chdejhgd.html:
>
>   The Cortex-A9 data cache implements an automatic prefetcher that
>   monitors cache misses done by the processor. This unit can monitor
>   and prefetch two independent data streams. It can be activated in
>   software using a CP15 Auxiliary Control Register bit. See Auxiliary
>   Control Register.
>
> This commit enables this L1 prefetch feature unconditionally on all
> Cortex-A9 by setting bit 2 in the Auxiliary Control CP15
> register. Note that since this bit only exists on Cortex-A9 but not on
> Cortex-A5 or Cortex-R7, we separate the handling of Cortex-A9 from the
> one of those two other cores.

Does this work in non-secure mode? Perhaps it is just ignored. If so,
it deserves a comment along the lines of "This bit should be set by
the bootloader and setting it has no effect in non-secure mode."

Rob

> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>  arch/arm/mm/proc-v7.S | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 3d1054f..106ea4d 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -257,8 +257,11 @@ ENDPROC(cpu_pj4b_do_resume)
>   *     It is assumed that:
>   *     - cache type register is implemented
>   */
> -__v7_ca5mp_setup:
>  __v7_ca9mp_setup:
> +       mov     r10, #(1 << 0)                  @ Cache/TLB ops broadcasting
> +       orr     r10, r10, #(1 << 2)             @ L1 prefetch
> +       b       1f
> +__v7_ca5mp_setup:
>  __v7_cr7mp_setup:
>         mov     r10, #(1 << 0)                  @ Cache/TLB ops broadcasting
>         b       1f
> --
> 2.1.0
>
>
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