From: Max Filippov <jcmvbkbc@gmail.com>
To: Chris Zankel <chris@zankel.net>
Cc: Marc Gauthier <marc@tensilica.com>,
linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org,
Max Filippov <jcmvbkbc@gmail.com>
Subject: [PATCH v2 03/11] xtensa: fix __delay for small loop count
Date: Fri, 30 Aug 2013 19:34:55 +0400 [thread overview]
Message-ID: <1377876903-27860-4-git-send-email-jcmvbkbc@gmail.com> (raw)
In-Reply-To: <1377876903-27860-1-git-send-email-jcmvbkbc@gmail.com>
Avoid __delay counter underflow for loop counts < 2.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
Changes v1->v2:
- make __delay fix more explicit for constant delays less than 2;
arch/xtensa/include/asm/delay.h | 9 ++++++---
1 files 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
--
1.7.7.6
next prev parent reply other threads:[~2013-08-30 15:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-30 15:34 [PATCH v2 00/11] xtensa queue 2013/08/30 Max Filippov
2013-08-30 15:34 ` [PATCH v2 01/11] xtensa: kernel: add "asm/ftrace.h" for pass compiling Max Filippov
2013-08-30 15:34 ` [PATCH v2 02/11] xtensa: fix arch spinlock function names Max Filippov
2013-08-30 15:34 ` Max Filippov [this message]
2013-08-30 15:34 ` [PATCH v2 04/11] xtensa: fix build warning Max Filippov
2013-08-30 15:34 ` [PATCH v2 05/11] xtensa: check thread flags atomically on return from user exception Max Filippov
2013-08-30 15:34 ` [PATCH v2 06/11] xtensa: enable kernel preemption Max Filippov
2013-08-30 15:34 ` [PATCH v2 07/11] xtensa: keep a3 and excsave1 on entry to exception handlers Max Filippov
2013-08-30 15:35 ` [PATCH v2 08/11] xtensa: new fast_alloca handler Max Filippov
2013-08-30 15:35 ` [PATCH v2 09/11] xtensa: don't use echo -e needlessly Max Filippov
2013-08-30 15:35 ` [PATCH v2 10/11] xtensa: fix !CONFIG_XTENSA_CALIBRATE_CCOUNT build failure Max Filippov
2013-08-30 15:35 ` [PATCH v2 11/11] xtensa: remove CCOUNT_PER_JIFFY Max Filippov
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