Re: [PATCH v3] rtc: omap: add support for pmic_power_en

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 27 Oct 2014 09:09:28 +0100 Johan Hovold <johan@kernel.org> 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@vger.kernel.org/msg82127.html
> 
> Tested-by: Felipe Balbi <balbi@ti.com>
> 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.