[openwrt/openwrt] kernel: set default values for ARM low level debugging symbols

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/721206a1b14fc5eba7ba8e20d979b26baf934e0d

commit 721206a1b14fc5eba7ba8e20d979b26baf934e0d
Author: Robert Marko <robimarko at gmail.com>
AuthorDate: Wed Feb 8 12:30:42 2023 +0100

    kernel: set default values for ARM low level debugging symbols
    
    Set default values for KERNEL_DEBUG_LL and KERNEL_DEBUG_LL_UART_NONE again
    as both of these symbols are non visible if KERNEL_EARLY_PRINTK is not
    selected and KConfig wont write their value to .config.
    
    This usually is the intended behaviour, but in OpenWrt we are relying on
    the KConfig to set these and disable the debug console settings that
    multiple targets like mvebu have set in their kernel config.
    This was the behaviour before removing all of the "default n" settings
    as KConfig by default considers symbols disabled but they are not visible
    anymore and thus their value is not set in .config and build system then
    later does not override the values from target kernel config.
    
    So, to restore the behaviour to the previous one lets a default value for
    KERNEL_DEBUG_LL and KERNEL_DEBUG_LL_UART_NONE.
    
    Fixes: 8bc72ea7be39 ("treewide: strip useless default n Kconfig lines")
    Tested-by: Georgi Valkov <gvalkov at gmail.com>
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 config/Config-kernel.in | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index 500f72672d..258163984e 100644
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -387,12 +387,18 @@ config KERNEL_DEBUG_INFO_REDUCED
 	  DEBUG_INFO build and compile times are reduced too.
 	  Only works with newer gcc versions.
 
+# KERNEL_DEBUG_LL symbols must have the default value set as otherwise
+# KConfig wont evaluate them unless KERNEL_EARLY_PRINTK is selected
+# which means that buildroot wont override the DEBUG_LL symbols in target
+# kernel configurations and lead to devices that dont have working console
 config KERNEL_DEBUG_LL_UART_NONE
 	bool
+	default n
 	depends on arm
 
 config KERNEL_DEBUG_LL
 	bool
+	default n
 	depends on arm
 	select KERNEL_DEBUG_LL_UART_NONE
 	help