parisc: Allow CONFIG_64BIT with ARCH=parisc

The previous patch triggered a build failure for the debian kernel,
which has CONFIG_64BIT enabled, uses the CROSS_COMPILER environment
variable and uses ARCH=parisc to configure the kernel for 64-bit
support.

This patch weakens the previous patch while keeping the recommended way
to configure the kernel with:
    ARCH=parisc     -> build 32-bit kernel
    ARCH=parisc64   -> build 64-bit kernel
while adding the possibility for debian to configure a 64-bit kernel
even if ARCH=parisc is set (PA8X00 CPU has to be selected and
CONFIG_64BIT needs to be enabled).

The downside of this patch is, that we now have a small window open
again where people may get it wrong: if they enable CONFIG_64BIT and try
to compile with a 32-bit compiler.

Fixes: 3dcfb729b5f4 ("parisc: Make CONFIG_64BIT available for ARCH=parisc64 only")
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # 5.15+

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 9aede2447011bc13f2fa11081d4ddb350784f285..a98940e6424327fe5a5232dc0613404c5c559ae4 100644 (file)
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -224,8 +224,18 @@ config MLONGCALLS
          Enabling this option will probably slow down your kernel.
 
 config 64BIT
-       def_bool "$(ARCH)" = "parisc64"
+       def_bool y if "$(ARCH)" = "parisc64"
+       bool "64-bit kernel" if "$(ARCH)" = "parisc"
        depends on PA8X00
+       help
+         Enable this if you want to support 64bit kernel on PA-RISC platform.
+
+         At the moment, only people willing to use more than 2GB of RAM,
+         or having a 64bit-only capable PA-RISC machine should say Y here.
+
+         Since there is no 64bit userland on PA-RISC, there is no point to
+         enable this option otherwise. The 64bit kernel is significantly bigger
+         and slower than the 32bit one.
 
 choice
        prompt "Kernel page size"