Discussion:
[PATCH] mvebu: disable CPU_IDLE as a Mamba instability workaround
(too old to reply)
Bjørn Mork
2018-03-19 09:51:01 UTC
Permalink
A regression seriously affecting the Linksys WRT1900ACv1 (Mamba) was
introduced some time between the OpenWrti/LEDE v4.4 and v4.9 kernels.
The root cause has not yet been identified, despite many attempts for
more than a year. However, disabling CPU_IDLE, and implicitly CPU_PM,
has been proven to be an effective workaround.

The symptoms on an affected system are unwanted reboots a a variable
frequency. In many cases almost immediately after boot, causing a
bootloop. This effectively disables support for Mamba on OpenWrt
with kernels > v4.4.

Disabling CPU_IDLE for now to reenable Mamba support.

Link: https://forum.lede-project.org/t/wrt1900acv1-reboots-kernel-4-9/2025
Signed-off-by: Bjørn Mork <***@mork.no>
---
target/linux/mvebu/config-4.14 | 4 ----
1 file changed, 4 deletions(-)

diff --git a/target/linux/mvebu/config-4.14 b/target/linux/mvebu/config-4.14
index 5286bf9b8314..78bed5b32f7b 100644
--- a/target/linux/mvebu/config-4.14
+++ b/target/linux/mvebu/config-4.14
@@ -54,7 +54,6 @@ CONFIG_ARM_HEAVY_MB=y
CONFIG_ARM_L1_CACHE_SHIFT=6
CONFIG_ARM_L1_CACHE_SHIFT_6=y
# CONFIG_ARM_LPAE is not set
-CONFIG_ARM_MVEBU_V7_CPUIDLE=y
CONFIG_ARM_PATCH_IDIV=y
CONFIG_ARM_PATCH_PHYS_VIRT=y
CONFIG_ARM_THUMB=y
@@ -103,11 +102,8 @@ CONFIG_CPU_FREQ_STAT=y
CONFIG_CPU_HAS_ASID=y
# CONFIG_CPU_HOTPLUG_STATE_CONTROL is not set
# CONFIG_CPU_ICACHE_DISABLE is not set
-CONFIG_CPU_IDLE=y
-CONFIG_CPU_IDLE_GOV_LADDER=y
CONFIG_CPU_PABRT_V7=y
CONFIG_CPU_PJ4B=y
-CONFIG_CPU_PM=y
CONFIG_CPU_RMAP=y
CONFIG_CPU_THERMAL=y
CONFIG_CPU_THUMB_CAPABLE=y
--
2.11.0
Felix Fietkau
2018-03-19 21:14:42 UTC
Permalink
Post by Bjørn Mork
A regression seriously affecting the Linksys WRT1900ACv1 (Mamba) was
introduced some time between the OpenWrti/LEDE v4.4 and v4.9 kernels.
The root cause has not yet been identified, despite many attempts for
more than a year. However, disabling CPU_IDLE, and implicitly CPU_PM,
has been proven to be an effective workaround.
The symptoms on an affected system are unwanted reboots a a variable
frequency. In many cases almost immediately after boot, causing a
bootloop. This effectively disables support for Mamba on OpenWrt
with kernels > v4.4.
Disabling CPU_IDLE for now to reenable Mamba support.
Link: https://forum.lede-project.org/t/wrt1900acv1-reboots-kernel-4-9/2025
Please try this variant instead, which should not affect unrelated devices:
https://git.openwrt.org/0142d447bc02922369c363de6510e76848943e9a

It's in my staging tree at
https://git.openwrt.org/?p=openwrt/staging/nbd.git;a=summary

Thanks,

- Felix
Bjørn Mork
2018-03-19 21:47:00 UTC
Permalink
Post by Felix Fietkau
Post by Bjørn Mork
A regression seriously affecting the Linksys WRT1900ACv1 (Mamba) was
introduced some time between the OpenWrti/LEDE v4.4 and v4.9 kernels.
The root cause has not yet been identified, despite many attempts for
more than a year. However, disabling CPU_IDLE, and implicitly CPU_PM,
has been proven to be an effective workaround.
The symptoms on an affected system are unwanted reboots a a variable
frequency. In many cases almost immediately after boot, causing a
bootloop. This effectively disables support for Mamba on OpenWrt
with kernels > v4.4.
Disabling CPU_IDLE for now to reenable Mamba support.
Link: https://forum.lede-project.org/t/wrt1900acv1-reboots-kernel-4-9/2025
https://git.openwrt.org/0142d447bc02922369c363de6510e76848943e9a
It's in my staging tree at
https://git.openwrt.org/?p=openwrt/staging/nbd.git;a=summary
Works for me. Thanks. Much better solution.


Bjørn
Zoltan HERPAI
2018-03-20 09:03:08 UTC
Permalink
Post by Bjørn Mork
Post by Felix Fietkau
Post by Bjørn Mork
A regression seriously affecting the Linksys WRT1900ACv1 (Mamba) was
introduced some time between the OpenWrti/LEDE v4.4 and v4.9 kernels.
The root cause has not yet been identified, despite many attempts for
more than a year. However, disabling CPU_IDLE, and implicitly CPU_PM,
has been proven to be an effective workaround.
The symptoms on an affected system are unwanted reboots a a variable
frequency. In many cases almost immediately after boot, causing a
bootloop. This effectively disables support for Mamba on OpenWrt
with kernels > v4.4.
Disabling CPU_IDLE for now to reenable Mamba support.
Link: https://forum.lede-project.org/t/wrt1900acv1-reboots-kernel-4-9/2025
https://git.openwrt.org/0142d447bc02922369c363de6510e76848943e9a
It's in my staging tree at
https://git.openwrt.org/?p=openwrt/staging/nbd.git;a=summary
Works for me. Thanks. Much better solution.
Confirmed fixing the reboot problem on another Mamba.

Regards,
Zoltan H

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