From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw02.freescale.net (az33egw02.freescale.net [192.88.158.103]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "az33egw02.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 291D7DDE00 for ; Tue, 28 Apr 2009 05:06:53 +1000 (EST) From: Timur Tabi To: linuxppc-dev@ozlabs.org, galak@kernel.crashing.org, benh@kernel.crashing.org, jwboyer@linux.vnet.ibm.com, scottwood@freescale.com Subject: [PATCH v6] introduce macro spin_event_timeout() Date: Mon, 27 Apr 2009 14:05:44 -0500 Message-Id: <1240859144-20893-1-git-send-email-timur@freescale.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , The macro spin_event_timeout() takes a condition and timeout value (in microseconds) as parameters. It spins until either the condition is true or the timeout expires. It returns the result of the condition when the loop was terminated. This primary purpose of this macro is to poll on a hardware register until a status bit changes. The timeout ensures that the loop still terminates if the bit doesn't change as expected. This macro makes it easier for driver developers to perform this kind of operation properly. Signed-off-by: Timur Tabi --- I'm making this a PowerPC-specific patch because I want to use tb_ticks_per_usec, which does not exist on all other platforms. I don't want to use jiffies because jiffies works only when interrupts are enabled, and the resolution may not be fine enough. arch/powerpc/include/asm/delay.h | 27 +++++++++++++++++++++++++++ 1 files changed, 27 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/include/asm/delay.h b/arch/powerpc/include/asm/delay.h index f9200a6..1939e0f 100644 --- a/arch/powerpc/include/asm/delay.h +++ b/arch/powerpc/include/asm/delay.h @@ -2,6 +2,8 @@ #define _ASM_POWERPC_DELAY_H #ifdef __KERNEL__ +#include + /* * Copyright 1996, Paul Mackerras. * @@ -30,5 +32,30 @@ extern void udelay(unsigned long usecs); #define mdelay(n) udelay((n) * 1000) #endif +/** + * spin_event_timeout - spin until a condition gets true or a timeout elapses + * @condition: a C expression to evalate + * @timeout: timeout, in microseconds + * @delay: the number of microseconds to delay between eache evaluation of + * @condition + * @rc: the last value of the condition + * + * The process spins until the condition evaluates to true (non-zero) or the + * timeout elapses. Upon exit, @rc contains the value of the condition. This + * allows you to test the condition without incurring any side effects. + * + * This primary purpose of this macro is to poll on a hardware register + * until a status bit changes. The timeout ensures that the loop still + * terminates if the bit never changes. The delay is for devices that need a + * delay in between successive reads. + */ +#define spin_event_timeout(condition, timeout, delay, rc) \ +{ \ + unsigned long __loops = tb_ticks_per_usec * timeout; \ + unsigned long __start = get_tbl(); \ + while (!(rc = (condition)) && (tb_ticks_since(__start) <= __loops)) \ + udelay(delay); \ +} + #endif /* __KERNEL__ */ #endif /* _ASM_POWERPC_DELAY_H */ -- 1.6.0.6