linux-kernel - Re: [PATCH v3 03/10] rtc: max77686: Use usleep

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Message-id: <20160127012105.GC14296@samsunx.samsung>
Date:	Wed, 27 Jan 2016 10:21:05 +0900
From:	Andi Shyti <andi.shyti@...sung.com>
To:	Javier Martinez Canillas <javier@....samsung.com>
Cc:	linux-kernel@...r.kernel.org, Kukjin Kim <kgene@...nel.org>,
	rtc-linux@...glegroups.com, Chanwoo Choi <cw00.choi@...sung.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v3 03/10] rtc: max77686: Use usleep_range() instead of
 msleep()

On Tue, Jan 26, 2016 at 04:20:13PM -0300, Javier Martinez Canillas wrote:
> Documentation/timers/timers-howto.txt suggest to use usleep_range()
> instead of msleep() for small msec (1ms - 20ms) since msleep() will
> often sleep for 20ms for any value in that range.
> 
> This is fine in this case since 16ms is the _minimum_ delay required
> by max77686 for an RTC update but by using usleep_range() instead of
> msleep(), the driver can support other RTC IP blocks with a shorter
> minimum delay (i.e: in the range of usecs instead of msecs).
> 
> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> Tested-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Reviewed-by: Andi Shyti <andi.shyti@...sung.com>

> ---
> 
> Changes in v3:
> - Add Krzysztof Kozlowski's Tested-by tag to patch #3.
> - Add Laxman Dewangan's Acked-by tag to patch #3.
> 
> Changes in v2:
> - Add Krzysztof Kozlowski's Reviewed-by tag to patch #3.
> - Fix typo error in changelog. Suggested by Krzysztof Kozlowski.
> 
>  drivers/rtc/rtc-max77686.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-max77686.c b/drivers/rtc/rtc-max77686.c
> index d84a50c9f7f7..025a17a95da3 100644
> --- a/drivers/rtc/rtc-max77686.c
> +++ b/drivers/rtc/rtc-max77686.c
> @@ -41,7 +41,7 @@
>  #define ALARM_ENABLE_SHIFT		7
>  #define ALARM_ENABLE_MASK		(1 << ALARM_ENABLE_SHIFT)
>  
> -#define MAX77686_RTC_UPDATE_DELAY	16
> +#define MAX77686_RTC_UPDATE_DELAY	16000
>  
>  enum {
>  	RTC_SEC = 0,
> @@ -130,7 +130,8 @@ static int max77686_rtc_update(struct max77686_rtc_info *info,
>  				__func__, ret, data);
>  	else {
>  		/* Minimum 16ms delay required before RTC update. */
> -		msleep(MAX77686_RTC_UPDATE_DELAY);
> +		usleep_range(MAX77686_RTC_UPDATE_DELAY,
> +			     MAX77686_RTC_UPDATE_DELAY * 2);
>  	}
>  
>  	return ret;
> -- 
> 2.5.0
> 
> --
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