Re: [PATCH] MIPS: Remove unused and erroneous div64.h

Hi,

Am 12.04.2021 um 05:34 schrieb Huacai Chen chenhuacai@kernel.org:

There are many errors in div64.h caused by commit c21004cd5b4cb7d479514 ("MIPS: Rewrite <asm/div64.h> to work with gcc 4.4.0."):

1, Only 32bit kernel need __div64_32(), but the above commit makes it depend on 64bit kernel by mistake. So div64.h is unused in fact.

2, asm-generic/div64.h should be included after __div64_32() definition.

3, __n should be initialized as *n before use (and "*__n >> 32" should be "__n >> 32") in __div64_32() definition.

4, linux/types.h should be included at the first place, otherwise BITS_ PER_LONG is not defined.

5, As Nikolaus, Yunqiang Su and Yanjie Zhou said, the MIPS-specific

s/Nikolaus/Nikolaus Schaller/

__div64_32() sometimes produces wrong results, which makes 32bit kernel boot fails.

I have tried to fix theses errors but I have failed with the last one. Yunqiang's tests show that the MIPS-specific __div64_32() has no obvious advantage than the C version, so I just simply remove div64.h.

This version works on both, alpha400/jz4730 and ci20/jz4780 (both 32 bit).

I have cross-checked the tree for *div64* files and only found as mips specific or lib files:

./arch/mips/include/generated/asm/div64.h -> #include <asm-generic/div64.h> ./include/asm-generic/div64.h ./lib/math/div64.c

So there were no remains from earlier compile runs.

And since it seems to have no advantage over the C version, I agree that we can remove the special code instead of wasting time to fix it.

Fixes: c21004cd5b4cb7d479514 ("MIPS: Rewrite <asm/div64.h> to work with gcc 4.4.0.") Cc: stable@vger.kernel.org

Tested-by: H. Nikolaus Schaller hns@goldelico.com # CI20/jz4780 and Alpha400/jz4730

BR and thanks, Nikolaus Schaller

Signed-off-by: Huacai Chen chenhuacai@loongson.cn

arch/mips/include/asm/div64.h | 68 ----------------------------------- 1 file changed, 68 deletions(-) delete mode 100644 arch/mips/include/asm/div64.h

diff --git a/arch/mips/include/asm/div64.h b/arch/mips/include/asm/div64.h deleted file mode 100644 index dc5ea5736440..000000000000 --- a/arch/mips/include/asm/div64.h +++ /dev/null @@ -1,68 +0,0 @@ -/*

• • Copyright (C) 2000, 2004 Maciej W. Rozycki
• • Copyright (C) 2003, 07 Ralf Baechle (ralf@linux-mips.org)
• • This file is subject to the terms and conditions of the GNU General Public
• • License. See the file "COPYING" in the main directory of this archive
• • for more details.
• */

-#ifndef __ASM_DIV64_H -#define __ASM_DIV64_H

-#include <asm-generic/div64.h>

-#if BITS_PER_LONG == 64

-#include <linux/types.h>

-/*

• • No traps on overflows for any of these...
• */

-#define __div64_32(n, base) \ -({ \

• unsigned long __cf, __tmp, __tmp2, __i; \
• unsigned long __quot32, __mod32; \
• unsigned long __high, __low; \
• unsigned long long __n; \

• 							\
  

• __high = *__n >> 32; \
• __low = __n; \
• __asm__( \
• " .set push \n" \
• " .set noat \n" \
• " .set noreorder \n" \
• " move %2, $0 \n" \
• " move %3, $0 \n" \
• " b 1f \n" \
• " li %4, 0x21 \n" \
• "0: \n" \
• " sll $1, %0, 0x1 \n" \
• " srl %3, %0, 0x1f \n" \
• " or %0, $1, %5 \n" \
• " sll %1, %1, 0x1 \n" \
• " sll %2, %2, 0x1 \n" \
• "1: \n" \
• " bnez %3, 2f \n" \
• " sltu %5, %0, %z6 \n" \
• " bnez %5, 3f \n" \
• "2: \n" \
• " addiu %4, %4, -1 \n" \
• " subu %0, %0, %z6 \n" \
• " addiu %2, %2, 1 \n" \
• "3: \n" \
• " bnez %4, 0b\n\t" \
• " srl %5, %1, 0x1f\n\t" \
• " .set pop" \
• : "=&r" (__mod32), "=&r" (__tmp), \

•  "=&r" (__quot32), "=&r" (__cf),				\
  

•  "=&r" (__i), "=&r" (__tmp2)					\
  

• : "Jr" (base), "0" (__high), "1" (__low)); \

• 							\
  

• (__n) = __quot32; \
• __mod32; \

-})

-#endif /* BITS_PER_LONG == 64 */

-#endif /* __ASM_DIV64_H */

2.27.0