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Message-ID: <17e2a135-274d-19d5-be26-58ec106cf0b5@collabora.com>
Date: Tue, 23 Jun 2020 16:19:05 +0100
From: Guillaume Tucker <guillaume.tucker@...labora.com>
To: kernelci-results@...ups.io, Krzysztof Kozlowski <krzk@...nel.org>
Cc: Russell King <linux@...linux.org.uk>,
linux-samsung-soc@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Kukjin Kim <kgene@...nel.org>
Subject: Re: krzysztof/for-next bisection: baseline.dmesg.crit on
bcm2837-rpi-3-b
On 23/06/2020 15:23, kernelci.org bot wrote:
> * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
> * This automated bisection report was sent to you on the basis *
> * that you may be involved with the breaking commit it has *
> * found. No manual investigation has been done to verify it, *
> * and the root cause of the problem may be somewhere else. *
> * *
> * If you do send a fix, please include this trailer: *
> * Reported-by: "kernelci.org bot" <bot@...nelci.org> *
> * *
> * Hope this helps! *
> * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
>
> krzysztof/for-next bisection: baseline.dmesg.crit on bcm2837-rpi-3-b
>
> Summary:
> Start: d6fe116541b7 Merge branch 'next/soc' into for-next
> Plain log: https://storage.kernelci.org/krzysztof/for-next/v5.8-rc1-14-gd6fe116541b7/arm64/defconfig+CONFIG_RANDOMIZE_BASE=y/gcc-8/lab-baylibre/baseline-bcm2837-rpi-3-b.txt
> HTML log: https://storage.kernelci.org/krzysztof/for-next/v5.8-rc1-14-gd6fe116541b7/arm64/defconfig+CONFIG_RANDOMIZE_BASE=y/gcc-8/lab-baylibre/baseline-bcm2837-rpi-3-b.html
> Result: 5b17a04addc2 ARM: exynos: clear L310_AUX_CTRL_FULL_LINE_ZERO in default l2c_aux_val
>
> Checks:
> revert: PASS
> verify: PASS
>
> Parameters:
> Tree: krzysztof
> URL: https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux.git
> Branch: for-next
> Target: bcm2837-rpi-3-b
> CPU arch: arm64
> Lab: lab-baylibre
> Compiler: gcc-8
> Config: defconfig+CONFIG_RANDOMIZE_BASE=y
> Test case: baseline.dmesg.crit
The "crit" kernel message is:
[ 17.566555] hwmon hwmon1: Undervoltage detected!
which does not seem to have anything to do with the patch found
by the bisection. Also, the bcm2837-rpi-3-b uses Cortex-A53
cores and no L2C-310 cache.
This undervoltage issue is actually an intermittent issue that
was already present before. See next-20200616:
https://kernelci.org/test/case/id/5ee880c10e8d4cd38797bf52/
https://storage.kernelci.org/next/master/next-20200616/arm64/defconfig/gcc-8/lab-baylibre/baseline-bcm2837-rpi-3-b.html#L708
I'll still take a closer look to be sure this is actually noise.
The same revision built without CONFIG_RAMDOMIZE_BASE=y passed
fine, although I don't see how this could be related:
https://kernelci.org/test/plan/id/5ef1ccb2d9df2557d597bf20/
Maybe the rpi-3-b could get an undervoltage depending on the
address where the kernel was loaded, and somehow my patch would
make this more likely? It sounds so far-fetched...
This is so ironic - after 6 months with no false positives in
kernelci bisections, and this rpi-3-b issue too random to ever
cause a bisection to succeed, I get this report which landed a
commit that I made, one week after enabling public bisection
email reports again. It must be trying to tell me something :)
Guillaume
> Breaking commit found:
>
> -------------------------------------------------------------------------------
> commit 5b17a04addc29201dc142c8d2c077eb7745d2e35
> Author: Guillaume Tucker <guillaume.tucker@...labora.com>
> Date: Fri Jun 12 14:58:37 2020 +0100
>
> 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
> commit 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>
> Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
>
> 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,
> -------------------------------------------------------------------------------
>
>
> Git bisection log:
>
> -------------------------------------------------------------------------------
> git bisect start
> # good: [b0953d8b7cdb39493e67cff4b20b0ebe3a2bba92] Merge branch 'next/drivers' into for-next
> git bisect good b0953d8b7cdb39493e67cff4b20b0ebe3a2bba92
> # bad: [d6fe116541b73a56110310c39a270c99766cd909] Merge branch 'next/soc' into for-next
> git bisect bad d6fe116541b73a56110310c39a270c99766cd909
> # bad: [5b17a04addc29201dc142c8d2c077eb7745d2e35] ARM: exynos: clear L310_AUX_CTRL_FULL_LINE_ZERO in default l2c_aux_val
> git bisect bad 5b17a04addc29201dc142c8d2c077eb7745d2e35
> # first bad commit: [5b17a04addc29201dc142c8d2c077eb7745d2e35] ARM: exynos: clear L310_AUX_CTRL_FULL_LINE_ZERO in default l2c_aux_val
> -------------------------------------------------------------------------------
>
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