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

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Date:	Tue, 26 Jan 2016 16:20:13 -0300
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	linux-kernel@...r.kernel.org
Cc:	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,
	Javier Martinez Canillas <javier@....samsung.com>
Subject: [PATCH v3 03/10] rtc: max77686: Use usleep_range() instead of msleep()

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>

---

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