From mboxrd@z Thu Jan 1 00:00:00 1970 From: Max Filippov Subject: [PATCH 05/17] xtensa: fix __delay for small loop count Date: Thu, 17 Oct 2013 02:42:16 +0400 Message-ID: <1381963348-29448-6-git-send-email-jcmvbkbc@gmail.com> References: <1381963348-29448-1-git-send-email-jcmvbkbc@gmail.com> Return-path: Received: from mail-lb0-f171.google.com ([209.85.217.171]:43441 "EHLO mail-lb0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760759Ab3JPWmy (ORCPT ); Wed, 16 Oct 2013 18:42:54 -0400 Received: by mail-lb0-f171.google.com with SMTP id u14so1198654lbd.16 for ; Wed, 16 Oct 2013 15:42:53 -0700 (PDT) In-Reply-To: <1381963348-29448-1-git-send-email-jcmvbkbc@gmail.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Chris Zankel Cc: Marc Gauthier , linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, Max Filippov Avoid __delay counter underflow for loop counts < 2. Signed-off-by: Max Filippov --- arch/xtensa/include/asm/delay.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/xtensa/include/asm/delay.h b/arch/xtensa/include/asm/delay.h index 3899610..742b89f 100644 --- a/arch/xtensa/include/asm/delay.h +++ b/arch/xtensa/include/asm/delay.h @@ -19,9 +19,12 @@ extern unsigned long loops_per_jiffy; static inline void __delay(unsigned long loops) { - /* 2 cycles per loop. */ - __asm__ __volatile__ ("1: addi %0, %0, -2; bgeui %0, 2, 1b" - : "=r" (loops) : "0" (loops)); + if (__builtin_constant_p(loops) && loops < 2) + __asm__ __volatile__ ("nop"); + else if (loops >= 2) + /* 2 cycles per loop. */ + __asm__ __volatile__ ("1: addi %0, %0, -2; bgeui %0, 2, 1b" + : "+r" (loops)); } /* For SMP/NUMA systems, change boot_cpu_data to something like -- 1.8.1.4