linux-kernel - Re: [RESEND PATCH 2/2] arm: socfpga: Set share override bit of the l2 cache controller

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Message-ID: <CAL_JsqKmbV69Q-hgnvnz-2+2T8k-Q+WcrFmewkfozKk06ZM7OA@mail.gmail.com>
Date:	Thu, 19 Feb 2015 12:13:13 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Dinh Nguyen <dinguyen@...nsource.altera.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Dinh Nguyen <dinh.linux@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Olof Johansson <olof@...om.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RESEND PATCH 2/2] arm: socfpga: Set share override bit of the l2
 cache controller

On Thu, Feb 19, 2015 at 11:06 AM,  <dinguyen@...nsource.altera.com> wrote:
> From: Dinh Nguyen <dinguyen@...nsource.altera.com>
>
> By not having bit 22 set in the PL310 Auxiliary Control register (shared
> attribute override enable) has the side effect of transforming Normal
> Shared Non-cacheable reads into Cacheable no-allocate reads.
>
> Coherent DMA buffers in Linux always have a Cacheable alias via the
> kernel linear mapping and the processor can speculatively load cache
> lines into the PL310 controller. With bit 22 cleared, Non-cacheable
> reads would unexpectedly hit such cache lines leading to buffer
> corruption.

You really should be doing this in your bootloader.

Rob

>
> Signed-off-by: Dinh Nguyen <dinguyen@...nsource.altera.com>
> ---
>  arch/arm/mach-socfpga/socfpga.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-socfpga/socfpga.c b/arch/arm/mach-socfpga/socfpga.c
> index a5f1fda..4ce2100 100644
> --- a/arch/arm/mach-socfpga/socfpga.c
> +++ b/arch/arm/mach-socfpga/socfpga.c
> @@ -105,7 +105,8 @@ static const char *altera_dt_match[] = {
>
>  DT_MACHINE_START(SOCFPGA, "Altera SOCFPGA")
>         .l2c_aux_val    = L310_AUX_CTRL_DATA_PREFETCH |
> -                         L310_AUX_CTRL_INSTR_PREFETCH,
> +                         L310_AUX_CTRL_INSTR_PREFETCH |
> +                         L2C_AUX_CTRL_SHARED_OVERRIDE,
>         .l2c_aux_mask   = ~0,
>         .smp            = smp_ops(socfpga_smp_ops),
>         .map_io         = socfpga_map_io,
> --
> 2.2.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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