From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wolverine02.qualcomm.com ([199.106.114.251]:13001 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752192Ab0LHEiz (ORCPT ); Tue, 7 Dec 2010 23:38:55 -0500 From: Stephen Boyd Subject: [PATCHv3 2/4] ARM: Allow machines to override __delay() Date: Tue, 7 Dec 2010 20:38:46 -0800 Message-Id: <1291783128-27520-3-git-send-email-sboyd@codeaurora.org> In-Reply-To: <1291783128-27520-1-git-send-email-sboyd@codeaurora.org> References: <1291783128-27520-1-git-send-email-sboyd@codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org List-ID: To: Russell King - ARM Linux Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Daniel Walker , Saravana Kannan , Nicolas Pitre , John Stultz , Brian Swetland , =?UTF-8?q?Arve=20Hj=F8nnev=E5g?= 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 | 19 ++++++++++++++++--- 2 files changed, 18 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 f92aca0..b38f7c0 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -11,11 +11,9 @@ #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" @@ -24,6 +22,21 @@ 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.