From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wolverine02.qualcomm.com ([199.106.114.251]:21899 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760272Ab0J1VTf (ORCPT ); Thu, 28 Oct 2010 17:19:35 -0400 From: Stephen Boyd Subject: [PATCHv2 2/3] ARM: Allow machines to override __delay() Date: Thu, 28 Oct 2010 14:19:29 -0700 Message-Id: <1288300770-18350-3-git-send-email-sboyd@codeaurora.org> In-Reply-To: <1288300770-18350-1-git-send-email-sboyd@codeaurora.org> References: <1288300770-18350-1-git-send-email-sboyd@codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org List-ID: To: Russell King Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Daniel Walker , Saravana Kannan , Colin Cross , Kevin Hilman , Santosh Shilimkar , Nicolas Pitre Some machines want to implement their own __delay() routine based on fixed rate timers. Expose functionality to set the __delay() routine at runtime. This should allow two machines with different __delay() routines to happily co-exist within the same kernel with minimal overhead. Russell expressed concern that using a timer based __delay() would cause problems when an iomapped device isn't mapped in prior to a delay call being made (see http://article.gmane.org/gmane.linux.ports.arm.kernel/78543 for more info). We can sidestep that issue with this approach since the __delay() routine _should_ only be pointed to a timer based delay once the timer has been properly mapped. Up until that point __delay() and udelay() will use delay_loop() which is always safe to call. This patch is inspired by x86's delay.c Signed-off-by: Stephen Boyd --- arch/arm/include/asm/delay.h | 2 ++ arch/arm/lib/delay.c | 21 ++++++++++++++++++--- 2 files changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index ccc5ed5..7c732b5 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -40,5 +40,7 @@ extern void __const_udelay(unsigned long); __const_udelay((n) * ((2199023U*HZ)>>11))) : \ __udelay(n)) +extern void set_delay_fn(void (*fn)(unsigned long)); + #endif /* defined(_ARM_DELAY_H) */ diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c index 1ab117d..116a853 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -3,6 +3,8 @@ * * Copyright (C) 1995, 1996 Russell King * Copyright (c) 2010, Code Aurora Forum. All rights reserved. + * Copyright (C) 1993 Linus Torvalds + * Copyright (C) 1997 Martin Mares * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as @@ -12,11 +14,9 @@ #include /* - * loops = usecs * HZ * loops_per_jiffy / 1000000 - * * Oh, if only we had a cycle counter... */ -void __delay(unsigned long loops) +void delay_loop(unsigned long loops) { asm volatile( "1: subs %0, %0, #1 \n" @@ -25,6 +25,21 @@ void __delay(unsigned long loops) : "r" (loops) ); } + +static void (*delay_fn)(unsigned long) = delay_loop; + +void set_delay_fn(void (*fn)(unsigned long)) +{ + delay_fn = fn; +} + +/* + * loops = usecs * HZ * loops_per_jiffy / 1000000 + */ +void __delay(unsigned long loops) +{ + delay_fn(loops); +} EXPORT_SYMBOL(__delay); /* -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.