From 2db4bc3418c43f1e810b304c48f8ddff2535075b Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Tue, 1 Apr 2014 00:57:28 +0100 Subject: [PATCH] MIPS: __delay CPU_DADDI_WORKAROUNDS bug fix With CPU_DADDI_WORKAROUNDS enabled __delay assembles with a macro in a branch delay slot: {standard input}: Assembler messages: {standard input}:18: Warning: Macro instruction expanded into multiple instructions in a branch delay slot and broken code results: 0000000000000000 <__delay>: 0: 1480ffff bnez a0,0 <__delay> 4: 24010001 li at,1 8: 0081202f dsubu a0,a0,at c: 03e00008 jr ra 10: 00000000 nop 14: 00000000 nop Consequently the function loops indefinitely, showing up prominently as a hang in the delay loop calibration at bootstrap. This change corrects the problem by forcing the immediate 1 into a register while keeping code produced identical where CPU_DADDI_WORKAROUNDS is disabled. Signed-off-by: Maciej W. Rozycki Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/6669/ Signed-off-by: Ralf Baechle --- arch/mips/lib/delay.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/mips/lib/delay.c b/arch/mips/lib/delay.c index 44713af15a6..705cfb7c1a7 100644 --- a/arch/mips/lib/delay.c +++ b/arch/mips/lib/delay.c @@ -6,7 +6,7 @@ * Copyright (C) 1994 by Waldorf Electronics * Copyright (C) 1995 - 2000, 01, 03 by Ralf Baechle * Copyright (C) 1999, 2000 Silicon Graphics, Inc. - * Copyright (C) 2007 Maciej W. Rozycki + * Copyright (C) 2007, 2014 Maciej W. Rozycki */ #include #include @@ -15,6 +15,12 @@ #include #include +#ifndef CONFIG_CPU_DADDI_WORKAROUNDS +#define GCC_DADDI_IMM_ASM() "I" +#else +#define GCC_DADDI_IMM_ASM() "r" +#endif + void __delay(unsigned long loops) { __asm__ __volatile__ ( @@ -22,13 +28,13 @@ void __delay(unsigned long loops) " .align 3 \n" "1: bnez %0, 1b \n" #if BITS_PER_LONG == 32 - " subu %0, 1 \n" + " subu %0, %1 \n" #else - " dsubu %0, 1 \n" + " dsubu %0, %1 \n" #endif " .set reorder \n" : "=r" (loops) - : "0" (loops)); + : GCC_DADDI_IMM_ASM() (1), "0" (loops)); } EXPORT_SYMBOL(__delay); -- 2.41.0