[OpenWrt-Devel] [PATCH] mvebu: disable CPU_IDLE as a Mamba instability workaround

[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
Signed-off-by: Bjørn Mork <bjorn at 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
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