powerpc: 32BIT vs. 64BIT (PPC32 vs. PPC64)

[Nicholas Piggin]

On Fri, 6 Jul 2018 21:58:29 -0700
Randy Dunlap <rdunlap at infradead.org> wrote:

> On 07/06/2018 06:45 PM, Benjamin Herrenschmidt wrote:
> > On Thu, 2018-07-05 at 14:30 -0700, Randy Dunlap wrote:  
> >> Hi,
> >>
> >> Is there a good way (or a shortcut) to do something like:
> >>
> >> $ make ARCH=powerpc O=PPC32 [other_options] allmodconfig
> >>   to get a PPC32/32BIT allmodconfig
> >>
> >> and also be able to do:
> >>
> >> $make ARCH=powerpc O=PPC64 [other_options] allmodconfig
> >>   to get a PPC64/64BIT allmodconfig?  
> > 
> > Hrm... O= is for the separate build dir, so there much be something
> > else.
> > 
> > You mean having ARCH= aliases like ppc/ppc32 and ppc64 ?  
> 
> Yes.
> 
> > That would be a matter of overriding some .config defaults I suppose, I
> > don't know how this is done on other archs.
> > 
> > I see the aliasing trick in the Makefile but that's about it.
> >   
> >> Note that arch/x86, arch/sh, and arch/sparc have ways to do
> >> some flavor(s) of this (from Documentation/kbuild/kbuild.txt;
> >> sh and sparc based on a recent "fix" patch from me):  
> > 
> > I fail to see what you are actually talking about here ... sorry. Do
> > you have concrete examples on x86 or sparc ? From what I can tell the
> > "i386" or "sparc32/sparc64" aliases just change SRCARCH in Makefile and
> > 32 vs 64-bit is just a Kconfig option...  
> 
> Yes, your summary is mostly correct.
> 
> I'm just looking for a way to do cross-compile builds that are close to
> ppc32 allmodconfig and ppc64 allmodconfig.

Would there a problem with adding ARCH=ppc32 / ppc64 matching? This
seems to work...

Thanks,
Nick

---
 Makefile                               | 8 ++++++++
 arch/powerpc/Kconfig                   | 9 +++++++++
 arch/powerpc/platforms/Kconfig.cputype | 8 --------
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index c5ce55cbc543..f97204aed17a 100644
--- a/Makefile
+++ b/Makefile
@@ -345,6 +345,14 @@ ifeq ($(ARCH),sh64)
        SRCARCH := sh
 endif
 
+# Additional ARCH settings for powerpc
+ifeq ($(ARCH),ppc32)
+       SRCARCH := powerpc
+endif
+ifeq ($(ARCH),ppc64)
+       SRCARCH := powerpc
+endif
+
 KCONFIG_CONFIG	?= .config
 export KCONFIG_CONFIG
 
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 9f2b75fe2c2d..3405b1b122be 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -1,4 +1,13 @@
 # SPDX-License-Identifier: GPL-2.0
+
+config PPC64
+	bool "64-bit kernel" if "$(ARCH)" = "powerpc"
+	default "$(ARCH)" != "ppc32"
+	select ZLIB_DEFLATE
+	help
+	  This option selects whether a 32-bit or a 64-bit kernel
+	  will be built.
+
 source "arch/powerpc/platforms/Kconfig.cputype"
 
 config PPC32
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index e6a1de521319..f6e5d6ef9782 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -1,12 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-config PPC64
-	bool "64-bit kernel"
-	default n
-	select ZLIB_DEFLATE
-	help
-	  This option selects whether a 32-bit or a 64-bit kernel
-	  will be built.
-
 menu "Processor support"
 choice
 	prompt "Processor Type"
-- 
2.17.0