linux-kernel - Re: [PATCH] ARM: exynos: clear L310_AUX_CTRL_FULL_LINE_ZERO in default l2c_aux

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Message-ID: <20200623061218.GA2983@kozik-lap>
Date:   Tue, 23 Jun 2020 08:12:18 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Guillaume Tucker <guillaume.tucker@...labora.com>
Cc:     Russell King <linux@...linux.org.uk>,
        Kukjin Kim <kgene@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH] ARM: exynos: clear L310_AUX_CTRL_FULL_LINE_ZERO in
 default l2c_aux_val

On Fri, Jun 12, 2020 at 02:58:37PM +0100, Guillaume Tucker wrote:
> This "alert" error message can be seen on exynos4412-odroidx2:
> 
>     L2C: platform modifies aux control register: 0x02070000 -> 0x3e470001
>     L2C: platform provided aux values permit register corruption.
> 
> Followed by this plain error message:
> 
>     L2C-310: enabling full line of zeros but not enabled in Cortex-A9
> 
> To fix it, don't set the L310_AUX_CTRL_FULL_LINE_ZERO flag (bit 0) in
> the default value of l2c_aux_val.  It may instead be enabled when
> applicable by the logic in l2c310_enable() if the attribute
> "arm,full-line-zero-disable" was set in the device tree.
> 
> The initial commit that introduced this default value was in v2.6.38:
> 
>   1cf0eb799759 "ARM: S5PV310: Add L2 cache init function in cpu.c"

Run checkpatch in the future on your patches.

I fixed it up.

Best regards,
Krzysztof

> 
> However, the code to set the L310_AUX_CTRL_FULL_LINE_ZERO flag and
> manage that feature was added much later and the default value was not
> updated then.  So this seems to have been a subtle oversight
> especially since enabling it only in the cache and not in the A9 core
> doesn't actually prevent the platform from running.  According to the
> TRM, the opposite would be a real issue, if the feature was enabled in
> the A9 core but not in the cache controller.
> 
> Reported-by: "kernelci.org bot" <bot@...nelci.org>
> Signed-off-by: Guillaume Tucker <guillaume.tucker@...labora.com>
> ---
>  arch/arm/mach-exynos/exynos.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
> index 7a8d1555db40..36c37444485a 100644
> --- a/arch/arm/mach-exynos/exynos.c
> +++ b/arch/arm/mach-exynos/exynos.c
> @@ -193,7 +193,7 @@ static void __init exynos_dt_fixup(void)
>  }
>  
>  DT_MACHINE_START(EXYNOS_DT, "Samsung Exynos (Flattened Device Tree)")
> -	.l2c_aux_val	= 0x3c400001,
> +	.l2c_aux_val	= 0x3c400000,
>  	.l2c_aux_mask	= 0xc20fffff,
>  	.smp		= smp_ops(exynos_smp_ops),
>  	.map_io		= exynos_init_io,
> -- 
> 2.20.1
>