ARM: 7073/1: debug: augment DEBUG_LL Kconfig help to clarify behaviour

Enabled DEBUG_LL hardcodes the UART address into the kernel and results
in a non-portable kernel image. Since this option is only intended for
use when debugging early boot failures, supporting multiple platforms
in such a configuration is not the intended use-case.

This patch documents this limitation in the DEBUG_LL Kconfig help text,
so that users are aware of the portability restrictions that are associated
with enabling low-level debugging support.

Reported-by: Sascha Hauer <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Russell King <[email protected]>

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 11604c9e55e0f2ec8c12c91d18a834bab775eb6a..60d18467795563f223d7671710d74649b5c797d5 100644 (file)
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -65,13 +65,18 @@ config DEBUG_USER
 
 # These options are only for real kernel hackers who want to get their hands dirty.
 config DEBUG_LL
-       bool "Kernel low-level debugging functions"
+       bool "Kernel low-level debugging functions (read help!)"
        depends on DEBUG_KERNEL
        help
          Say Y here to include definitions of printascii, printch, printhex
          in the kernel.  This is helpful if you are debugging code that
          executes before the console is initialized.
 
+         Note that selecting this option will limit the kernel to a single
+         UART definition, as specified below. Attempting to boot the kernel
+         image on a different platform *will not work*, so this option should
+         not be enabled for kernels that are intended to be portable.
+
 choice
        prompt "Kernel low-level debugging port"
        depends on DEBUG_LL