On Mon, 27 Oct 2014 09:09:28 +0100 Johan Hovold [off-list ref] wrote:

Add new property "ti,system-power-controller" to register the RTC as a
power-off handler.

Some RTC IP revisions can control an external PMIC via the pmic_power_en
pin, which can be configured to transition to OFF on ALARM2 events and
back to ON on subsequent ALARM (wakealarm) events.

This is based on earlier work by Colin Foe-Parker and AnilKumar Ch. [1]

[1] https://www.mail-archive.com/linux-omap at vger.kernel.org/msg82127.html

Tested-by: Felipe Balbi <redacted>
Signed-off-by: Johan Hovold <johan@kernel.org>
---

Changes since v2:
 - add two-second delay to allow alarm to trigger before returning

hmpf.  As this sentence is below the ^--- it doesn't get into the
changelog.

...

+static void omap_rtc_power_off(void)
+{
+	struct omap_rtc *rtc = omap_rtc_power_off_rtc;
+	struct rtc_time tm;
+	unsigned long now;
+	u32 val;
+
+	/* enable pmic_power_en control */
+	val = rtc_readl(rtc, OMAP_RTC_PMIC_REG);
+	rtc_writel(rtc, OMAP_RTC_PMIC_REG, val | OMAP_RTC_PMIC_POWER_EN_EN);
+
+	/* set alarm two seconds from now */
+	omap_rtc_read_time_raw(rtc, &tm);
+	bcd2tm(&tm);
+	rtc_tm_to_time(&tm, &now);
+	rtc_time_to_tm(now + 2, &tm);
+
+	if (tm2bcd(&tm) < 0) {
+		dev_err(&rtc->rtc->dev, "power off failed\n");
+		return;
+	}
+
+	rtc_wait_not_busy(rtc);
+
+	rtc_write(rtc, OMAP_RTC_ALARM2_SECONDS_REG, tm.tm_sec);
+	rtc_write(rtc, OMAP_RTC_ALARM2_MINUTES_REG, tm.tm_min);
+	rtc_write(rtc, OMAP_RTC_ALARM2_HOURS_REG, tm.tm_hour);
+	rtc_write(rtc, OMAP_RTC_ALARM2_DAYS_REG, tm.tm_mday);
+	rtc_write(rtc, OMAP_RTC_ALARM2_MONTHS_REG, tm.tm_mon);
+	rtc_write(rtc, OMAP_RTC_ALARM2_YEARS_REG, tm.tm_year);
+
+	/*
+	 * enable ALARM2 interrupt
+	 *
+	 * NOTE: this fails on AM3352 if rtc_write (writeb) is used
+	 */
+	val = rtc_read(rtc, OMAP_RTC_INTERRUPTS_REG);
+	rtc_writel(rtc, OMAP_RTC_INTERRUPTS_REG,
+			val | OMAP_RTC_INTERRUPTS_IT_ALARM2);
+
+	mdelay(2000);

And it is uncommented.

How on earth is a reader to know why this is here?

I can do this

--- a/drivers/rtc/rtc-omap.c~rtc-omap-add-support-for-pmic_power_en-v3-fix
+++ a/drivers/rtc/rtc-omap.c

@@ -417,6 +417,7 @@ static void omap_rtc_power_off(void)
 	rtc_writel(rtc, OMAP_RTC_INTERRUPTS_REG,
 			val | OMAP_RTC_INTERRUPTS_IT_ALARM2);
 
+	/* Allow alarm to trigger before returning */
 	mdelay(2000);
 }
 

But it doesn't explain *why* we want the alarm to trigger before
returning.