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

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Message-Id: <c6d979c0050502cd1bca8619cb5ff95db239db12.1591969825.git.guillaume.tucker@collabora.com>
Date:   Fri, 12 Jun 2020 14:58:37 +0100
From:   Guillaume Tucker <guillaume.tucker@...labora.com>
To:     Russell King <linux@...linux.org.uk>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     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: [PATCH] ARM: exynos: clear L310_AUX_CTRL_FULL_LINE_ZERO in default l2c_aux_val

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"

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