ppc little-endian port

ppc little-endian port

[Alexandre Nikolaev]

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Hello everyone!

This is a port of Montavista's 2.4.0-test2 kernel to ppc running in
Little-Endian.
As a base, we used Sandpoint configuration, but disabled some irrelevant
code for our board (these changes are not in the patch).
We made it just for a board with CPU and RAM only, so if you want to use
anything extra (drives, PCI, etc.)
you have to look at the corresponding code and make changes accordingly
(if needed). Additionally, if you use different configuration scheme
(not sandpoint), you might have to do some other changes.

Sebastien Cote: cots01@gel.usherb.ca

Alexandre Nikoalev: anikolae@matrox.com

--
*****************************************
| Alexandre Nikolaev
| Software Designer
| Matrox Electronic Systems Ltd
| Imaging Department
| Tel. (514) 8226000 ext. 2323
| E-mail: Alexandre_Nikolaev@matrox.com
*****************************************:)


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diff -ru /usr/src/redhat/SOURCES/linux/arch/ppc/Makefile ./arch/ppc/Makefile
--- /usr/src/redhat/SOURCES/linux/arch/ppc/Makefile	Mon Jun 19 20:59:35 2000
+++ ./arch/ppc/Makefile	Fri Apr  6 14:03:29 2001
@@ -23,7 +23,7 @@
 CPPFLAGS	:= $(CPPFLAGS) -D__powerpc__
 CFLAGS		:= $(CFLAGS) -D__powerpc__ -fsigned-char \
 		-msoft-float -pipe -ffixed-r2 -Wno-uninitialized \
-		-mmultiple -mstring
+#		-mmultiple -mstring
 CPP		= $(CC) -E $(CFLAGS)

 ifdef CONFIG_4xx
diff -ru /usr/src/redhat/SOURCES/linux/arch/ppc/kernel/hashtable.S ./arch/ppc/kernel/hashtable.S
--- /usr/src/redhat/SOURCES/linux/arch/ppc/kernel/hashtable.S	Mon Jun 19 20:59:36 2000
+++ ./arch/ppc/kernel/hashtable.S	Fri Apr  6 15:05:24 2001
@@ -321,7 +321,7 @@

 	/* Search the primary PTEG for a PTE whose 1st word matches r5 */
 	mtctr	r2
-	addi	r3,r4,-8
+	addi	r3,r4,-4		/* Changed from -8 to -4 by me !!!! */
 1:	lwzu	r0,8(r3)		/* get next PTE */
 	cmp	0,r0,r5
 	bdnzf	2,1b			/* loop while ctr != 0 && !cr0.eq */
@@ -333,7 +333,7 @@
 hash_page_patch_B:
 	xoris	r3,r4,Hash_msk>>16	/* compute secondary hash */
 	xori	r3,r3,0xffc0
-	addi	r3,r3,-8
+	addi	r3,r3,-4		/* Changed from -8 to -4 by me !!!! */
 	mtctr	r2
 2:	lwzu	r0,8(r3)
 	cmp	0,r0,r5
@@ -343,7 +343,8 @@

 	/* Search the primary PTEG for an empty slot */
 10:	mtctr	r2
-	addi	r3,r4,-8		/* search primary PTEG */
+	addi	r3,r4,-4		/* search primary PTEG */
+					/* Changed from -8 to -4 by me !!!! */
 1:	lwzu	r0,8(r3)		/* get next PTE */
 	rlwinm.	r0,r0,0,0,0		/* only want to check valid bit */
 	bdnzf	2,1b			/* loop while ctr != 0 && !cr0.eq */
@@ -355,7 +356,7 @@
 hash_page_patch_C:
 	xoris	r3,r4,Hash_msk>>16	/* compute secondary hash */
 	xori	r3,r3,0xffc0
-	addi	r3,r3,-8
+	addi	r3,r3,-4		/* Changed from -8 to -4 by me !!!! */
 	mtctr	r2
 2:
 	lwzu	r0,8(r3)
@@ -380,6 +381,7 @@
 	andi.	r2,r2,0x38
 	stw	r2,next_slot@l(r3)
 	add	r3,r4,r2
+	addi	r3,r3,4			/* Add 4 to realign data, by me !!!! */
 11:
 	/* update counter of evicted pages */
 	lis	r2,htab_evicts@ha
@@ -393,7 +395,7 @@
 found_empty:
 	stw	r5,0(r3)
 found_slot:
-	stw	r6,4(r3)
+	stw	r6,-4(r3)	/* Changed to -4 to preserve LE by me !!!! */
 	sync

 #else /* CONFIG_SMP */
@@ -543,7 +545,7 @@
 	lwz	r6,Hash_size@l(r6)	/* size in bytes */
 	srwi	r6,r6,3			/* # PTEs */
 	mtctr	r6
-	addi	r5,r5,-8
+	addi	r5,r5,-4		/* Changed from -8 to -4 by me !!!! */
 	li	r0,0
 1:	lwzu	r6,8(r5)		/* get next tag word */
 	cmplw	0,r6,r3
@@ -642,7 +644,7 @@
 	add	r6,r6,r7		/* address of primary PTEG */
 	li	r8,8
 	mtctr	r8
-	addi	r7,r6,-8
+	addi	r7,r6,-4		/* Changed from -8 to -4 by me !!!! */
 1:	lwzu	r0,8(r7)		/* get next PTE */
 	cmpw	0,r0,r3			/* see if tag matches */
 	bdnzf	2,1b			/* while --ctr != 0 && !cr0.eq */
@@ -650,7 +652,7 @@
 	ori	r3,r3,0x40		/* set H (alt. hash) bit */
 	xor	r6,r6,r5		/* address of secondary PTEG */
 	mtctr	r8
-	addi	r7,r6,-8
+	addi	r7,r6,-4		/* Changed from -8 to -4 by me !!!! */
 2:	lwzu	r0,8(r7)		/* get next PTE */
 	cmpw	0,r0,r3			/* see if tag matches */
 	bdnzf	2,2b			/* while --ctr != 0 && !cr0.eq */
diff -ru /usr/src/redhat/SOURCES/linux/arch/ppc/kernel/head.S ./arch/ppc/kernel/head.S
--- /usr/src/redhat/SOURCES/linux/arch/ppc/kernel/head.S	Fri Apr  6 13:56:40 2001
+++ ./arch/ppc/kernel/head.S	Mon Apr 23 09:10:11 2001
@@ -292,11 +299,14 @@
 label:						\
 	EXCEPTION_PROLOG;			\
 	addi	r3,r1,STACK_FRAME_OVERHEAD;	\
-	li	r20,MSR_KERNEL;			\
+	lis	r20,MSR_KERNEL@ha;		\
+	addi	r20,r20,MSR_KERNEL@l;		\
 	bl	transfer_to_handler; 		\
 	.long	hdlr;				\
 	.long	ret_from_except

+	/* Loading of MSR_KERNEL changed by me !!!! */
+
 /* System reset */
 #ifdef CONFIG_SMP /* MVME/MTX and gemini start the secondary here */
 #ifdef CONFIG_GEMINI
@@ -333,7 +343,9 @@
 	mfspr	r4,DAR
 	stw	r4,_DAR(r21)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL*/
+        lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	do_page_fault
@@ -347,7 +359,9 @@
 	mfspr	r4,DAR
 	stw	r4,_DAR(r21)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL  Replaced by me !!!!*/
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	UnknownException
@@ -372,7 +386,9 @@
 1:	addi	r3,r1,STACK_FRAME_OVERHEAD
 	mr	r4,r22
 	mr	r5,r23
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	do_page_fault
@@ -384,7 +400,9 @@
 	b	InstructionSegment
 InstructionSegmentCont:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL  Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	UnknownException
@@ -396,7 +414,9 @@
 HardwareInterrupt:
 	EXCEPTION_PROLOG;
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 #ifndef CONFIG_APUS
 	li	r4,0
 	bl	transfer_to_handler
@@ -417,7 +437,9 @@
 	mfspr	r5,DSISR
 	stw	r5,_DSISR(r21)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	AlignmentException
@@ -428,7 +450,9 @@
 ProgramCheck:
 	EXCEPTION_PROLOG
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	ProgramCheckException
@@ -438,8 +462,17 @@
 	. = 0x800
 FPUnavailable:
 	EXCEPTION_PROLOG
 	bne	load_up_fpu		/* if from user, just load it up */
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	bl	transfer_to_handler	/* if from kernel, take a trap */
 	.long	KernelFP
 	.long	ret_from_except
@@ -448,7 +481,9 @@
 Decrementer:
 	EXCEPTION_PROLOG
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	bl	transfer_to_handler
 	.globl timer_interrupt_intercept
 timer_interrupt_intercept:
@@ -463,7 +498,9 @@
 SystemCall:
 	EXCEPTION_PROLOG
 	stw	r3,ORIG_GPR3(r21)
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
 	bl	transfer_to_handler
 	.long	DoSyscall
@@ -484,7 +521,9 @@
 	b	Trap_0f
 trap_0f_cont:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	bl	transfer_to_handler
 	.long	UnknownException
 	.long	ret_from_except
@@ -706,8 +745,17 @@
 #ifdef CONFIG_ALTIVEC
 AltiVecUnavailable:
 	EXCEPTION_PROLOG
 	bne	load_up_altivec		/* if from user, just load it up */
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL	Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	bl	transfer_to_handler	/* if from kernel, take a trap */
 	.long	KernelAltiVec
 	.long	ret_from_except
@@ -785,7 +839,9 @@
 	addi	r1,r1,TASK_UNION_SIZE-STACK_FRAME_OVERHEAD
 	lis	r24,StackOverflow@ha
 	addi	r24,r24,StackOverflow@l
-	li	r20,MSR_KERNEL
+	/*li	r20,MSR_KERNEL Replaced by me !!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	FIX_SRR1(r20,r22)
 	mtspr	SRR0,r24
 	mtspr	SRR1,r20
@@ -1213,7 +1269,9 @@
 	stw	r3,(_CCR+4)(r21);

 	addi	r3,r1,STACK_FRAME_OVERHEAD;
-	li	r20,MSR_KERNEL;
+	/*li	r20,MSR_KERNEL;	Replaced by me !!!!! */
+	lis	r20,MSR_KERNEL@ha
+	addi	r20,r20,MSR_KERNEL@l
 	bl	transfer_to_handler;
 	.long	do_IRQ;
 	.long	ret_from_except
@@ -1288,7 +1346,9 @@
 	mtspr	SPRG2,r3	/* 0 => r1 has kernel sp */

 	/* enable MMU and jump to start_secondary */
-	li	r4,MSR_KERNEL
+	/*li	r4,MSR_KERNEL	Replaced by me !!!! */
+	lis	r4,MSR_KERNEL@ha
+	addi	r4,r4,MSR_KERNEL@l
 	lis	r3,start_secondary@h
 	ori	r3,r3,start_secondary@l
 	mtspr	SRR0,r3
@@ -1452,7 +1516,9 @@
 	lis	r4,2f@h
 	ori	r4,r4,2f@l
 	tophys(r4,r4)
-	li	r3,MSR_KERNEL & ~(MSR_IR|MSR_DR)
+	/*li	r3,MSR_KERNEL & ~(MSR_IR|MSR_DR)    Replaced by me !!!! */
+	lis	r3,(MSR_KERNEL & ~(MSR_IR|MSR_DR))@ha
+	addi	r3,r3,(MSR_KERNEL & ~(MSR_IR|MSR_DR))@l
 	FIX_SRR1(r3,r5)
 	mtspr	SRR0,r4
 	mtspr	SRR1,r3
@@ -1470,7 +1536,10 @@

 	bl	load_up_mmu
 /* Now turn on the MMU for real! */
-	li	r4,MSR_KERNEL
+	/*li	r4,MSR_KERNEL Replaced by me !!!! */
+	lis	r4,MSR_KERNEL@ha
+	addi	r4,r4,MSR_KERNEL@l
+
 	FIX_SRR1(r4,r5)
 	lis	r3,start_kernel@h
 	ori	r3,r3,start_kernel@l
diff -ru /usr/src/redhat/SOURCES/linux/arch/ppc/kernel/irq.c ./arch/ppc/kernel/irq.c
--- /usr/src/redhat/SOURCES/linux/arch/ppc/kernel/irq.c	Mon Jun 19 20:59:36 2000
+++ ./arch/ppc/kernel/irq.c	Fri Apr  6 15:29:33 2001
@@ -349,7 +349,8 @@
 	else
 		once++;

-	ppc_md.init_IRQ();
+	if (ppc_md.init_IRQ)       /* Added by me !!!! */
+	        ppc_md.init_IRQ();
 }

 #ifdef CONFIG_SMP
Only in /usr/src/redhat/SOURCES/linux/arch/ppc/mbxboot: vmlinux.lds
Only in /usr/src/redhat/SOURCES/linux/drivers/pcmcia: Config.in.orig
diff -ru /usr/src/redhat/SOURCES/linux/include/asm-ppc/bitops.h ./include/asm-ppc/bitops.h
--- /usr/src/redhat/SOURCES/linux/include/asm-ppc/bitops.h	Mon Jun 19 20:59:37 2000
+++ ./include/asm-ppc/bitops.h	Wed Apr 11 13:50:25 2001
@@ -242,8 +242,12 @@
  * test_and_{set,clear}_bit guarantee atomicity without
  * disabling interrupts.
  */
+#if 0
 #define ext2_set_bit(nr, addr)		test_and_set_bit((nr) ^ 0x18, addr)
 #define ext2_clear_bit(nr, addr)	test_and_clear_bit((nr) ^ 0x18, addr)
+#endif /* Replaced by me !!!! (to remove XOR) */
+#define ext2_set_bit(nr, addr)		test_and_set_bit((nr), addr)
+#define ext2_clear_bit(nr, addr)	test_and_clear_bit((nr), addr)

 #else
 extern __inline__ int ext2_set_bit(int nr, void * addr)
diff -ru /usr/src/redhat/SOURCES/linux/include/asm-ppc/byteorder.h ./include/asm-ppc/byteorder.h
--- /usr/src/redhat/SOURCES/linux/include/asm-ppc/byteorder.h	Mon Jun 19 20:59:37 2000
+++ ./include/asm-ppc/byteorder.h	Fri Apr  6 14:34:22 2001
@@ -9,7 +9,7 @@

 #ifdef __GNUC__

-extern __inline__ unsigned ld_le16(const volatile unsigned short *addr)
+extern __inline__ unsigned ld_be16(const volatile unsigned short *addr)
 {
 	unsigned val;

@@ -17,12 +17,12 @@
 	return val;
 }

-extern __inline__ void st_le16(volatile unsigned short *addr, const unsigned val)
+extern __inline__ void st_be16(volatile unsigned short *addr, const unsigned val)
 {
 	__asm__ __volatile__ ("sthbrx %1,0,%2" : "=m" (*addr) : "r" (val), "r" (addr));
 }

-extern __inline__ unsigned ld_le32(const volatile unsigned *addr)
+extern __inline__ unsigned ld_be32(const volatile unsigned *addr)
 {
 	unsigned val;

@@ -30,7 +30,7 @@
 	return val;
 }

-extern __inline__ void st_le32(volatile unsigned *addr, const unsigned val)
+extern __inline__ void st_be32(volatile unsigned *addr, const unsigned val)
 {
 	__asm__ __volatile__ ("stwbrx %1,0,%2" : "=m" (*addr) : "r" (val), "r" (addr));
 }
@@ -71,18 +71,21 @@
 #endif

 /* The same, but returns converted value from the location pointer by addr. */
-#define __arch__swab16p(addr) ld_le16(addr)
-#define __arch__swab32p(addr) ld_le32(addr)
+#define __arch__swab16p(addr) ld_be16(addr)
+#define __arch__swab32p(addr) ld_be32(addr)

 /* The same, but do the conversion in situ, ie. put the value back to addr. */
-#define __arch__swab16s(addr) st_le16(addr,*addr)
-#define __arch__swab32s(addr) st_le32(addr,*addr)
+#define __arch__swab16s(addr) st_be16(addr,*addr)
+#define __arch__swab32s(addr) st_be32(addr,*addr)

 #endif /* __GNUC__ */

+/* All "le" changed to "be", and vice-versa, by me !!!! */
+
 #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
 #define __BYTEORDER_HAS_U64__
 #endif
-#include <linux/byteorder/big_endian.h>
+#include <linux/byteorder/little_endian.h>
+/* Changed from big_endian to little_endian by me !!!! */

 #endif /* _PPC_BYTEORDER_H */
diff -ru /usr/src/redhat/SOURCES/linux/include/asm-ppc/io.h ./include/asm-ppc/io.h
--- /usr/src/redhat/SOURCES/linux/include/asm-ppc/io.h	Mon Jun 19 20:59:37 2000
+++ ./include/asm-ppc/io.h	Wed Apr 11 13:50:26 2001
@@ -231,7 +231,7 @@
 	__asm__ __volatile__("stb%U0%X0 %1,%0; eieio" : "=m" (*addr) : "r" (val));
 }

-extern inline int in_le16(volatile unsigned short *addr)
+extern inline int in_be16(volatile unsigned short *addr)
 {
 	int ret;

@@ -240,7 +240,7 @@
 	return ret;
 }

-extern inline int in_be16(volatile unsigned short *addr)
+extern inline int in_le16(volatile unsigned short *addr)
 {
 	int ret;

@@ -248,18 +248,18 @@
 	return ret;
 }

-extern inline void out_le16(volatile unsigned short *addr, int val)
+extern inline void out_be16(volatile unsigned short *addr, int val)
 {
 	__asm__ __volatile__("sthbrx %1,0,%2; eieio" : "=m" (*addr) :
 			      "r" (val), "r" (addr));
 }

-extern inline void out_be16(volatile unsigned short *addr, int val)
+extern inline void out_le16(volatile unsigned short *addr, int val)
 {
 	__asm__ __volatile__("sth%U0%X0 %1,%0; eieio" : "=m" (*addr) : "r" (val));
 }

-extern inline unsigned in_le32(volatile unsigned *addr)
+extern inline unsigned in_be32(volatile unsigned *addr)
 {
 	unsigned ret;

@@ -268,7 +268,7 @@
 	return ret;
 }

-extern inline unsigned in_be32(volatile unsigned *addr)
+extern inline unsigned in_le32(volatile unsigned *addr)
 {
 	unsigned ret;

@@ -276,13 +276,13 @@
 	return ret;
 }

-extern inline void out_le32(volatile unsigned *addr, int val)
+extern inline void out_be32(volatile unsigned *addr, int val)
 {
 	__asm__ __volatile__("stwbrx %1,0,%2; eieio" : "=m" (*addr) :
 			     "r" (val), "r" (addr));
 }

-extern inline void out_be32(volatile unsigned *addr, int val)
+extern inline void out_le32(volatile unsigned *addr, int val)
 {
 	__asm__ __volatile__("stw%U0%X0 %1,%0; eieio" : "=m" (*addr) : "r" (val));
 }
diff -ru /usr/src/redhat/SOURCES/linux/include/asm-ppc/processor.h ./include/asm-ppc/processor.h
--- /usr/src/redhat/SOURCES/linux/include/asm-ppc/processor.h	Fri Apr  6 13:56:37 2001
+++ ./include/asm-ppc/processor.h	Wed Apr 11 13:50:25 2001
@@ -45,7 +45,8 @@
 #ifdef CONFIG_APUS_FAST_EXCEPT
 #define MSR_		MSR_ME|MSR_IP|MSR_RI
 #else
-#define MSR_		MSR_ME|MSR_RI
+#define MSR_		MSR_ME|MSR_RI|MSR_LE|MSR_ILE
+/* MSD_LE and MSR_ILE added by me !!!! */
 #endif
 #define MSR_KERNEL      MSR_|MSR_IR|MSR_DR
 #define MSR_USER	MSR_KERNEL|MSR_PR|MSR_EE

Re: ppc little-endian port

[Cort Dougan]

Why?

} This is a port of Montavista's 2.4.0-test2 kernel to ppc running in
} Little-Endian.
} As a base, we used Sandpoint configuration, but disabled some irrelevant
} code for our board (these changes are not in the patch).
} We made it just for a board with CPU and RAM only, so if you want to use
} anything extra (drives, PCI, etc.)
} you have to look at the corresponding code and make changes accordingly
} (if needed). Additionally, if you use different configuration scheme
} (not sandpoint), you might have to do some other changes.

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: ppc little-endian port

[Dan Malek]

Cort Dougan wrote:
>
> Why?

Yeah, we really don't care about little-endian.  Like I always
say, getting a kernel built and booted is the easy part.  The
entire world runs big endian tools, libraries and applications.
Making all of that work is a task no one is going to tackle.

While refreshing my PowerPC history the other day, I found a UISA
book from 1991.....The Little-Endian Byte Ordering chapter introduction
has this to say:

	It is computed that eleven Thousand Persons have, at several
	Times, suffered Death, rather than submit to break their
	Eggs at the smaller End.  Many hundred large Volumes have been
	published upon this Controversy...

			Jonathan Swift, "Gulliver's Travels"

Later in the text it states "There are 24 ways to specify the
ordering of four bytes withing a word, but only two of these
orderings are sensible."

I contend there is only one sensible ordering, and we are already
using it.........


	-- Dan

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Re: ppc little-endian port

[Gabriel Paubert]

On Mon, 23 Apr 2001, Dan Malek wrote:

>
> Cort Dougan wrote:
> >
> > Why?
>
> Yeah, we really don't care about little-endian.  Like I always
> say, getting a kernel built and booted is the easy part.  The
> entire world runs big endian tools, libraries and applications.
> Making all of that work is a task no one is going to tackle.

Indeed...

> While refreshing my PowerPC history the other day, I found a UISA
> book from 1991.....The Little-Endian Byte Ordering chapter introduction
> has this to say:

1991 ? I though PPC came in 1993. First Power systems were announced and
delivered in 1990 AFAIR.

> Later in the text it states "There are 24 ways to specify the
> ordering of four bytes withing a word, but only two of these
> orderings are sensible."

Indeed the PDP was a nightmare, like VAX floating-point formats BTW...

> I contend there is only one sensible ordering, and we are already
> using it.........

Right, unfortunately so many people have been brainwashed by the
niadne-elttil side and are unable to think on their own.

	Regards,
	Gabriel.


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Re: ppc little-endian port

[Alexandre Nikolaev]

Sorry, we were not clear enough...

Why we did it:
            We have our own image processing PCI board. Hardware guys
decided that since PCI is little endian, it would be better from "their
hardware point of view" to run ppc in little-endian as well. We can do
nothing about that and just have to run ppc in little endian.
Maybe someone else will be on the same boat :)

What else we did:
            We compiled the whole Busy Box using glibc with some
modifications of glibc (endian related + strange bug). Also, we compiled
the ash of standard source (taken from Montavista) using Dietlibc with
no modifications. Then we compiled and run an application under ash
shell (yieldt benchmark from Montavista) and saw good results: typically
7 ms and 11 ms thread context switch time regardless of number of
threads and thread size, for revisions 2.09 and 2.06 respectfully.

Which processors did we test:
            We ran only 7400, revision 2.06 and 2.09.

Alexandre



*****************************************
| Alexandre Nikolaev
| Software Designer
| Matrox Electronic Systems Ltd
| Imaging Department
| Tel. (514) 8226000 ext. 2323
| E-mail: Alexandre_Nikolaev@matrox.com
*****************************************:)


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RE: ppc little-endian port

[Zehetbauer Thomas]

Thank's for the patch Alexandre & Sebastien !

For those who need to ask 'why': We want^H^H^H^Hneed interoperatbility
with no hazzles between the big world running on little endian x86
systems and those little devices designed by people who have not left
their protected labs for years.

Tom

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Re: ppc little-endian port

[Albert D. Cahalan]

Dan Malek writes:
> Cort Dougan wrote:
>
>> Why?
>
> Yeah, we really don't care about little-endian.  Like I always
> say, getting a kernel built and booted is the easy part.  The
> entire world runs big endian tools, libraries and applications.
> Making all of that work is a task no one is going to tackle.

I'm going to tackle it. Alexandre Nikolaev already is tackling
it I guess.

Lots of PowerPC processors run in little-endian mode today.
They could be running Linux if the ppc port was as flexible
as the mips port. Modern medical scanners (CAT, MRI, PET...)
all use little-endian PowerPC processors. So if I need to get
my head examined, I'll be doing it with little-endian. :-)

Now that you know, please avoid writing endian-dependent code.
The hard-coded offsets that Alexandre Nikolaev had to change
should have been done with a #define. We're going to have to
fix this; expect patches within a year.

> While refreshing my PowerPC history the other day, I found a UISA
> book from 1991.....The Little-Endian Byte Ordering chapter introduction
> has this to say:
>
>         It is computed that eleven Thousand Persons have, at several
>         Times, suffered Death, rather than submit to break their
>         Eggs at the smaller End.  Many hundred large Volumes have been
>         published upon this Controversy...
>
>                         Jonathan Swift, "Gulliver's Travels"
>
> Later in the text it states "There are 24 ways to specify the
> ordering of four bytes withing a word, but only two of these
> orderings are sensible."
>
> I contend there is only one sensible ordering, and we are already
> using it.........

>From best to worst:

1. true little-endian, as found on IBM's 405 (and on x86)
2. true big-endian, default on the PowerPC
3. crappy "little-endian" hack, as found on Motorola's 7400
4. crappy "big-endian" hack, as found on the Alpha
5. anything else

Opinions on this don't matter when you put a 7400 on a PCI board
and try to share memory with an x86 host computer. In this case
you do whatever is needed to make user-space data structures look
the same to both processors. This may include both hardware and
compiler hacking, as well as the more obvious OS and libc hacks.

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Re: ppc little-endian port

[Dan Malek]

"Albert D. Cahalan" wrote:

> I'm going to tackle it. Alexandre Nikolaev already is tackling
> it I guess.

That's way beyond the scope of discussion or interest on this
list.  Make sure you contact the proper tools, library, and
application folks.

> Lots of PowerPC processors run in little-endian mode today.

Lots?  Maybe a few.  Since the first days of PowerPC I have only
seen one ill-fated attempt.  Every time I'm part of a PPC silicon
design discussion the question is always raised whether it is
worth wasting silicon trying to support it.

It's getting harder to use little endian on PowerPC.  The 7450 has
only a big endian bus, with some weird lane swapping internally.
Misaligned little endian accesses still cause processor exceptions,
and the 7450 states it doesn't support it at all (some contradiction
here), so you are always at a performance disadvantage when using
it.  Besides, the bytes are all backward from the normal order of
the world and you end up spending cycles swapping them, anyway :-).

> .... Modern medical scanners (CAT, MRI, PET...)
> all use little-endian PowerPC processors.

It can't be all, because I have worked on some prototypes in the
past that weren't.

> Opinions on this don't matter when you put a 7400 on a PCI board
> and try to share memory with an x86 host computer.

My opinions always matter :-).  In this case you should be using
a big-endian PowerPC host computer, too.


	-- Dan

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Re: ppc little-endian port

[Ralph Blach]

[-- Attachment #1: Type: text/plain, Size: 1077 bytes --]

Dan Malek wrote:
>

> > Lots of PowerPC processors run in little-endian mode today.
>
Dan,

All 40x processor models support propper little endian. And the 4xx do
NOT get Alignment exceptions for
missaligned data.  So no performance penalty.  On the 4xx it is NOT
getting harder to use little endian,
Its as  easy as just setting the bits.


Chip

> Lots?  Maybe a few.  Since the first days of PowerPC I have only
> seen one ill-fated attempt.  Every time I'm part of a PPC silicon
> design discussion the question is always raised whether it is
> worth wasting silicon trying to support it.
>
> It's getting harder to use little endian on PowerPC.  The 7450 has
> only a big endian bus, with some weird lane swapping internally.
> Misaligned little endian accesses still cause processor exceptions,
> and the 7450 states it doesn't support it at all (some contradiction
> here), so you are always at a performance disadvantage when using
> it.  Besides, the bytes are all backward from the normal order of
> the world and you end up spending cycles swapping them, anyway :-).

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email;internet:rcblach@raleigh.ibm.com
x-mozilla-cpt:;15936
fn:Ralph Blach
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Re: ppc little-endian port

[Cort Dougan]

I think IBM made sure that the 4xx series was hard enough to use without
concern about endian-ness.  In that respect, the 4xx is endian fair.

} On the 4xx it is NOT
} getting harder to use little endian,

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Re: ppc little-endian port

[Albert D. Cahalan]

Dan Malek writes:
> "Albert D. Cahalan" wrote:

>> I'm going to tackle it. Alexandre Nikolaev already is tackling
>> it I guess.
>
> That's way beyond the scope of discussion or interest on this
> list.  Make sure you contact the proper tools, library, and
> application folks.

Huh? This is the linuxppc-embedded list if I'm not mistaken.
Do you mean that this discussion belongs on a list where the
workstation developers can participate?

(ouch, must switch mode after calling Open Firmware)

>> Lots of PowerPC processors run in little-endian mode today.
>
> Lots?  Maybe a few.  Since the first days of PowerPC I have only
> seen one ill-fated attempt.  Every time I'm part of a PPC silicon
> design discussion the question is always raised whether it is
> worth wasting silicon trying to support it.

Dropping little-endian would seriously piss off Motorola's #2
customer for high-end PowerPC chips.

> It's getting harder to use little endian on PowerPC.  The 7450 has
> only a big endian bus, with some weird lane swapping internally.

This matters for what, IO accesses? Normal memory access is in
large chunks to feed the cache. The 7450 manual looks an awful
lot like the 7400 manual. Perhaps you can supply a chapter and
section number.

> Misaligned little endian accesses still cause processor exceptions,

Good. Misaligned big-endian accesses perform poorly. The mere
existance of a little-endian port will help you get better
performance in big-endian mode because the bad alignment gets
cleaned up.

> and the 7450 states it doesn't support it at all (some contradiction
> here), so you are always at a performance disadvantage when using
> it.  Besides, the bytes are all backward from the normal order of
> the world and you end up spending cycles swapping them, anyway :-).

The normal order of the world is little-endian, given the
dominance of PCI and PC data formats. Big-endian is a mistake
that won't die because it was written into network standards.

Performance? Here: lhbrx, lwbrx, sthbrx, stwbrx

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Re: ppc little-endian port

[Dan Malek]

"Albert D. Cahalan" wrote:

> Huh? This is the linuxppc-embedded list if I'm not mistaken.

Well, it was originally created for developers to discuss embedded
PowerPC Linux kernel issues.  It wasn't appropriate to discuss that
on the workstation list, although some of us participate on all lists
to ensure nothing is missed.  This list has since turned into a support
desk function, which isn't the intention.

> Do you mean that this discussion belongs on a list where the
> workstation developers can participate?

No, not even there.  There are developer lists for tools, libraries
and applications.  You need to find the places where the developers
for the compilers, binutils, libraries and such hang out.  We seldom
discuss any of that here, unless there is some kernel interface issue
that has to be coordinated with them.


> Dropping little-endian would seriously piss off Motorola's #2
> customer for high-end PowerPC chips.

...and who may that be?  A #2 customer should have high visibility
here (and I've seen the list, so I would like to know where people
really think they are on it).

> The normal order of the world is little-endian, given the
> dominance of PCI and PC data formats. Big-endian is a mistake
> that won't die because it was written into network standards.

You don't get out much, do you :-)?  Lighten up a little, this
is supposed to be fun.......We could argue all day, but there was
lots of computer work done before PCI and PCs.  I'm more than old
enough to know, so just leave it at that.......


	-- Dan

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