Patch "rtc: sun6i: Switch to the external oscillator" has been added to the 4.4-stable tree

Patch "rtc: sun6i: Switch to the external oscillator" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    rtc: sun6i: Switch to the external oscillator

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rtc-sun6i-switch-to-the-external-oscillator.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From fb61bb82cb46a932ef2fc62e1c731c8e7e6640d5 Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime.ripard@free-electrons.com>
Date: Mon, 23 Jan 2017 11:41:48 +0100
Subject: rtc: sun6i: Switch to the external oscillator

From: Maxime Ripard <maxime.ripard@free-electrons.com>

commit fb61bb82cb46a932ef2fc62e1c731c8e7e6640d5 upstream.

The RTC is clocked from either an internal, imprecise, oscillator or an
external one, which is usually much more accurate.

The difference perceived between the time elapsed and the time reported by
the RTC is in a 10% scale, which prevents the RTC from being useful at all.

Fortunately, the external oscillator is reported to be mandatory in the
Allwinner datasheet, so we can just switch to it.

Fixes: 9765d2d94309 ("rtc: sun6i: Add sun6i RTC driver")
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/rtc/rtc-sun6i.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c
@@ -37,9 +37,11 @@
 
 /* Control register */
 #define SUN6I_LOSC_CTRL				0x0000
+#define SUN6I_LOSC_CTRL_KEY			(0x16aa << 16)
 #define SUN6I_LOSC_CTRL_ALM_DHMS_ACC		BIT(9)
 #define SUN6I_LOSC_CTRL_RTC_HMS_ACC		BIT(8)
 #define SUN6I_LOSC_CTRL_RTC_YMD_ACC		BIT(7)
+#define SUN6I_LOSC_CTRL_EXT_OSC			BIT(0)
 #define SUN6I_LOSC_CTRL_ACC_MASK		GENMASK(9, 7)
 
 /* RTC */
@@ -417,6 +419,10 @@ static int sun6i_rtc_probe(struct platfo
 	/* disable alarm wakeup */
 	writel(0, chip->base + SUN6I_ALARM_CONFIG);
 
+	/* switch to the external, more precise, oscillator */
+	writel(SUN6I_LOSC_CTRL_KEY | SUN6I_LOSC_CTRL_EXT_OSC,
+	       chip->base + SUN6I_LOSC_CTRL);
+
 	chip->rtc = rtc_device_register("rtc-sun6i", &pdev->dev,
 					&sun6i_rtc_ops, THIS_MODULE);
 	if (IS_ERR(chip->rtc)) {


Patches currently in stable-queue which might be from maxime.ripard@free-electrons.com are

queue-4.4/rtc-sun6i-add-some-locking.patch
queue-4.4/rtc-sun6i-switch-to-the-external-oscillator.patch