linux-kernel - RE: [PATCH V3 05/10] ARM: OMAP2+: SmartReflex: introduce a busy loop condition test macro

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Date:	Fri, 4 May 2012 09:12:13 +0000
From:	"AnilKumar, Chimata" <anilkumar@...com>
To:	"J, KEERTHY" <j-keerthy@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Hilman, Kevin" <khilman@...com>, "rjw@...k.pl" <rjw@...k.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>
CC:	"Pihet-XID, Jean" <j-pihet@...com>
Subject: RE: [PATCH V3 05/10] ARM: OMAP2+: SmartReflex: introduce a busy
 loop condition test macro

On Thu, Apr 26, 2012 at 23:10:36, J, KEERTHY wrote:
> From: Jean Pihet <j-pihet@...com>
> 
> Now that omap_test_timeout is only accessible from mach-omap2/,
> introduce a similar function for SR.
> 
> This change makes the SmartReflex implementation ready for the move
> to drivers/.
> 
> Signed-off-by: Jean Pihet <j-pihet@...com>
> Signed-off-by: J Keerthy <j-keerthy@...com>
> ---
>  arch/arm/mach-omap2/smartreflex.c |   12 ++++++------
>  include/linux/power/smartreflex.h |   23 ++++++++++++++++++++++-
>  2 files changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/smartreflex.c b/arch/arm/mach-omap2/smartreflex.c
> index d859277..acef08d 100644
> --- a/arch/arm/mach-omap2/smartreflex.c
> +++ b/arch/arm/mach-omap2/smartreflex.c
> @@ -289,9 +289,9 @@ static void sr_v1_disable(struct omap_sr *sr)
>  	 * Wait for SR to be disabled.
>  	 * wait until ERRCONFIG.MCUDISACKINTST = 1. Typical latency is 1us.
>  	 */
> -	omap_test_timeout((sr_read_reg(sr, ERRCONFIG_V1) &
> -			ERRCONFIG_MCUDISACKINTST), SR_DISABLE_TIMEOUT,
> -			timeout);
> +	sr_test_cond_timeout((sr_read_reg(sr, ERRCONFIG_V1) &
> +			     ERRCONFIG_MCUDISACKINTST), SR_DISABLE_TIMEOUT,
> +			     timeout);
>  
>  	if (timeout >= SR_DISABLE_TIMEOUT)
>  		dev_warn(&sr->pdev->dev, "%s: Smartreflex disable timedout\n",
> @@ -334,9 +334,9 @@ static void sr_v2_disable(struct omap_sr *sr)
>  	 * Wait for SR to be disabled.
>  	 * wait until IRQSTATUS.MCUDISACKINTST = 1. Typical latency is 1us.
>  	 */
> -	omap_test_timeout((sr_read_reg(sr, IRQSTATUS) &
> -			IRQSTATUS_MCUDISABLEACKINT), SR_DISABLE_TIMEOUT,
> -			timeout);
> +	sr_test_cond_timeout((sr_read_reg(sr, IRQSTATUS) &
> +			     IRQSTATUS_MCUDISABLEACKINT), SR_DISABLE_TIMEOUT,
> +			     timeout);
>  
>  	if (timeout >= SR_DISABLE_TIMEOUT)
>  		dev_warn(&sr->pdev->dev, "%s: Smartreflex disable timedout\n",
> diff --git a/include/linux/power/smartreflex.h b/include/linux/power/smartreflex.h
> index 884eaee..78b795e 100644
> --- a/include/linux/power/smartreflex.h
> +++ b/include/linux/power/smartreflex.h
> @@ -22,7 +22,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/platform_device.h>
> -
> +#include <linux/delay.h>
>  #include <plat/voltage.h>
>  
>  /*
> @@ -168,6 +168,27 @@ struct omap_sr {
>  };
>  
>  /**
> + * test_cond_timeout - busy-loop, testing a condition
> + * @cond: condition to test until it evaluates to true
> + * @timeout: maximum number of microseconds in the timeout
> + * @index: loop index (integer)
> + *
> + * Loop waiting for @cond to become true or until at least @timeout
> + * microseconds have passed.  To use, define some integer @index in the
> + * calling code.  After running, if @index == @timeout, then the loop has
> + * timed out.
> + *
> + * Copied from omap_test_timeout */
> +#define sr_test_cond_timeout(cond, timeout, index)		\
> +({								\
> +	for (index = 0; index < timeout; index++) {		\
> +		if (cond)					\
> +			break;					\
> +		udelay(1);					\
> +	}							\
> +})

I think we can use time_after()/time_before() APIs for timeout and cpu_relax() for
tight loops instead of udelay().

Regards
AnilKumar
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