linux-kernel - [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs

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Date:   Fri,  9 Jun 2017 12:48:06 -0700
From:   Babu Moger <babu.moger@...cle.com>
To:     ysato@...rs.sourceforge.jp, geert@...ux-m68k.org,
        jonas@...thpole.se, stefan.kristiansson@...nalahti.fi,
        shorne@...il.com, jejb@...isc-linux.org, deller@....de,
        davem@...emloft.net, viro@...iv.linux.org.uk
Cc:     mpe@...erman.id.au, peterz@...radead.org, mingo@...hat.com,
        jcmvbkbc@...il.com, linux-kernel@...r.kernel.org,
        uclinux-h8-devel@...ts.sourceforge.jp, linux-m68k@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        sparclinux@...r.kernel.org
Subject: [PATCH v2 1/2] arch: Define CPU_BIG_ENDIAN for all fixed big endian archs

While working on enabling queued rwlock on SPARC, found
this following code in include/asm-generic/qrwlock.h
which uses CONFIG_CPU_BIG_ENDIAN to clear a byte.

static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
 {
	return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
 }

Problem is many of the fixed big endian architectures don't define
CPU_BIG_ENDIAN and clears the wrong byte.

Define CPU_BIG_ENDIAN for all the fixed big endian architecture to fix it.

Also found few more references of this config parameter in
drivers/of/base.c
drivers/of/fdt.c
drivers/tty/serial/earlycon.c
drivers/tty/serial/serial_core.c
Be aware that this may cause regressions if someone has worked-around
problems in the above code already. Remove the work-around.

Here is our original discussion
https://lkml.org/lkml/2017/5/24/620

Signed-off-by: Babu Moger <babu.moger@...cle.com>
Suggested-by: Arnd Bergmann <arnd@...db.de>
Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Acked-by: David S. Miller <davem@...emloft.net>
---
 arch/frv/Kconfig      |    3 +++
 arch/h8300/Kconfig    |    3 +++
 arch/m68k/Kconfig     |    3 +++
 arch/openrisc/Kconfig |    3 +++
 arch/parisc/Kconfig   |    3 +++
 arch/sparc/Kconfig    |    3 +++
 6 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig
index eefd9a4..1cce824 100644
--- a/arch/frv/Kconfig
+++ b/arch/frv/Kconfig
@@ -17,6 +17,9 @@ config FRV
 	select HAVE_DEBUG_STACKOVERFLOW
 	select ARCH_NO_COHERENT_DMA_MMAP
 
+config CPU_BIG_ENDIAN
+	def_bool y
+
 config ZONE_DMA
 	bool
 	default y
diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
index 3ae8525..5380ac8 100644
--- a/arch/h8300/Kconfig
+++ b/arch/h8300/Kconfig
@@ -23,6 +23,9 @@ config H8300
 	select HAVE_ARCH_HASH
 	select CPU_NO_EFFICIENT_FFS
 
+config CPU_BIG_ENDIAN
+	def_bool y
+
 config RWSEM_GENERIC_SPINLOCK
 	def_bool y
 
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index d140206..029a58b 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -23,6 +23,9 @@ config M68K
 	select OLD_SIGSUSPEND3
 	select OLD_SIGACTION
 
+config CPU_BIG_ENDIAN
+	def_bool y
+
 config RWSEM_GENERIC_SPINLOCK
 	bool
 	default y
diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 1e95920..a0f2e4a 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -29,6 +29,9 @@ config OPENRISC
 	select CPU_NO_EFFICIENT_FFS if !OPENRISC_HAVE_INST_FF1
 	select NO_BOOTMEM
 
+config CPU_BIG_ENDIAN
+	def_bool y
+
 config MMU
 	def_bool y
 
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 531da9e..dda1f55 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -47,6 +47,9 @@ config PARISC
 	  and later HP3000 series).  The PA-RISC Linux project home page is
 	  at <http://www.parisc-linux.org/>.
 
+config CPU_BIG_ENDIAN
+	def_bool y
+
 config MMU
 	def_bool y
 
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 58243b0..eb213b5 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -92,6 +92,9 @@ config ARCH_DEFCONFIG
 config ARCH_PROC_KCORE_TEXT
 	def_bool y
 
+config CPU_BIG_ENDIAN
+	def_bool y
+
 config ARCH_ATU
 	bool
 	default y if SPARC64
-- 
1.7.1