From patchwork Wed Oct 23 21:29:16 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Helge Deller X-Patchwork-Id: 3089941 Return-Path: X-Original-To: patchwork-linux-parisc@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 409179F2B7 for ; Wed, 23 Oct 2013 21:29:25 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 23B0B203AD for ; Wed, 23 Oct 2013 21:29:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4819C2039C for ; Wed, 23 Oct 2013 21:29:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751830Ab3JWV3V (ORCPT ); Wed, 23 Oct 2013 17:29:21 -0400 Received: from mout.gmx.net ([212.227.15.18]:63188 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751504Ab3JWV3V (ORCPT ); Wed, 23 Oct 2013 17:29:21 -0400 Received: from p100.box ([84.173.50.36]) by mail.gmx.com (mrgmx103) with ESMTPSA (Nemesis) id 0Lhf3N-1W4Fjz1xFh-00mpRz for ; Wed, 23 Oct 2013 23:29:19 +0200 Date: Wed, 23 Oct 2013 23:29:16 +0200 From: Helge Deller To: linux-parisc@vger.kernel.org, James Bottomley Subject: [PATCH] parisc: make udelay() SMP-safe Message-ID: <20131023212916.GA1529@p100.box> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-Provags-ID: V03:K0:DGBvpGMnmdJ7Tbf2PROXzNLkekOUBGYgIrFPgJHIhLgi5Lc8yPp SuAYGkCjjHGIyWqGgMte2QOZtCub5GOYxbrIL/fXCeogvtgDV0G1lBoCzzMtwFju0rp0QFU s4f9UolMGSHfCihAz9rWox/hAKKIAamBQ9aenH7mW9twA3B52SiJOydtUw6t8gWj1jQX66z v3I/wb9/K+PIxqruD18zQ== Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org X-Spam-Status: No, score=-7.3 required=5.0 tests=BAYES_00,FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Each CPU has it's own Control Register 16 (CR16) which is used as time source for the udelay() function. But since the CR16 registers across different CPUs are not synced, we need to recalculate the loop count if we get switched away to ensure that we really delay as much time as requested. Signed-off-by: Helge Deller --- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/arch/parisc/include/asm/delay.h b/arch/parisc/include/asm/delay.h index 912ee7e..08e58e6 100644 --- a/arch/parisc/include/asm/delay.h +++ b/arch/parisc/include/asm/delay.h @@ -1,15 +1,5 @@ -#ifndef _PARISC_DELAY_H -#define _PARISC_DELAY_H - -#include /* for mfctl() */ -#include /* for boot_cpu_data */ - - -/* - * Copyright (C) 1993 Linus Torvalds - * - * Delay routines - */ +#ifndef _ASM_PARISC_DELAY_H +#define _ASM_PARISC_DELAY_H static __inline__ void __delay(unsigned long loops) { asm volatile( @@ -19,25 +9,14 @@ static __inline__ void __delay(unsigned long loops) { : "=r" (loops) : "0" (loops)); } -static __inline__ void __cr16_delay(unsigned long clocks) { - unsigned long start; - - /* - * Note: Due to unsigned math, cr16 rollovers shouldn't be - * a problem here. However, on 32 bit, we need to make sure - * we don't pass in too big a value. The current default - * value of MAX_UDELAY_MS should help prevent this. - */ +extern void __udelay(unsigned long usecs); +extern void __udelay_bad(unsigned long usecs); - start = mfctl(16); - while ((mfctl(16) - start) < clocks) - ; +static inline void udelay(unsigned long usecs) +{ + if (__builtin_constant_p(usecs) && (usecs) > 20000) + __udelay_bad(usecs); + __udelay(usecs); } -static __inline__ void __udelay(unsigned long usecs) { - __cr16_delay(usecs * ((unsigned long)boot_cpu_data.cpu_hz / 1000000UL)); -} - -#define udelay(n) __udelay(n) - -#endif /* defined(_PARISC_DELAY_H) */ +#endif /* _ASM_PARISC_DELAY_H */ diff --git a/arch/parisc/lib/Makefile b/arch/parisc/lib/Makefile index 5651536..8fa92b8 100644 --- a/arch/parisc/lib/Makefile +++ b/arch/parisc/lib/Makefile @@ -3,6 +3,6 @@ # lib-y := lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o \ - ucmpdi2.o + ucmpdi2.o delay.o obj-y := iomap.o diff --git a/arch/parisc/lib/delay.c b/arch/parisc/lib/delay.c new file mode 100644 index 0000000..b1fb528 --- /dev/null +++ b/arch/parisc/lib/delay.c @@ -0,0 +1,73 @@ +/* + * Precise Delay Loops for parisc + * + * based on code by: + * Copyright (C) 1993 Linus Torvalds + * Copyright (C) 1997 Martin Mares + * Copyright (C) 2008 Jiri Hladky + * + * parisc implementation: + * Copyright (C) 2013 Helge Deller + */ + + +#include +#include +#include + +#include +#include + +#include /* for mfctl() */ +#include /* for boot_cpu_data */ + +/* CR16 based delay: */ +static void __cr16_delay(unsigned long __loops) +{ + /* + * Note: Due to unsigned math, cr16 rollovers shouldn't be + * a problem here. However, on 32 bit, we need to make sure + * we don't pass in too big a value. The current default + * value of MAX_UDELAY_MS should help prevent this. + */ + u32 bclock, now, loops = __loops; + int cpu; + + preempt_disable(); + cpu = smp_processor_id(); + bclock = mfctl(16); + for (;;) { + now = mfctl(16); + if ((now - bclock) >= loops) + break; + + /* Allow RT tasks to run */ + preempt_enable(); + asm volatile(" nop\n"); + barrier(); + preempt_disable(); + + /* + * It is possible that we moved to another CPU, and + * since CR16's are per-cpu we need to calculate + * that. The delay must guarantee that we wait "at + * least" the amount of time. Being moved to another + * CPU could make the wait longer but we just need to + * make sure we waited long enough. Rebalance the + * counter for this CPU. + */ + if (unlikely(cpu != smp_processor_id())) { + loops -= (now - bclock); + cpu = smp_processor_id(); + bclock = mfctl(16); + } + } + preempt_enable(); +} + + +void __udelay(unsigned long usecs) +{ + __cr16_delay(usecs * ((unsigned long)boot_cpu_data.cpu_hz / 1000000UL)); +} +EXPORT_SYMBOL(__udelay);