[v4,2/4] rtc: OMAP: Add support for rtc-only mode

Prepare rtc driver for rtc-only with DDR in self-refresh mode.
omap_rtc_power_off now should cater to two features:

1) RTC plus DDR in self-refresh is power a saving mode where in the
entire system including the different voltage rails from PMIC are
shutdown except the ones feeding on to RTC and DDR. DDR is kept in
self-refresh hence the contents are preserved. RTC ALARM2 is connected
to PMIC_EN line once we the ALARM2 is triggered we enter the mode with
DDR in self-refresh and RTC Ticking. After a predetermined time an RTC
ALARM1 triggers waking up the system[1]. The control goes to bootloader.
The bootloader then checks RTC scratchpad registers to confirm it was an
rtc_only wakeup and follows a different path, configure bare minimal
clocks for ddr and then jumps to the resume address in another RTC
scratchpad registers and transfers the control to Kernel. Kernel then
restores the saved context. omap_rtc_power_off_program does the ALARM2
programming part.

     [1] http://www.ti.com/lit/ug/spruhl7h/spruhl7h.pdf Page 2884

2) Power-off: This is usual poweroff mode. omap_rtc_power_off calls the
above omap_rtc_power_off_program function and in addition to that
programs the OMAP_RTC_PMIC_REG for any external wake ups for PMIC like
the pushbutton and shuts off the PMIC.

Hence the split in omap_rtc_power_off.

Signed-off-by: Keerthy <j-keerthy@ti.com>
---
 drivers/rtc/rtc-omap.c | 53 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 38 insertions(+), 15 deletions(-)

On Thu, Jul 12, 2018 at 10:37:38AM +0530, Keerthy wrote:
> Prepare rtc driver for rtc-only with DDR in self-refresh mode.
> omap_rtc_power_off now should cater to two features:
> 
> 1) RTC plus DDR in self-refresh is power a saving mode where in the
> entire system including the different voltage rails from PMIC are
> shutdown except the ones feeding on to RTC and DDR. DDR is kept in
> self-refresh hence the contents are preserved. RTC ALARM2 is connected
> to PMIC_EN line once we the ALARM2 is triggered we enter the mode with
> DDR in self-refresh and RTC Ticking. After a predetermined time an RTC
> ALARM1 triggers waking up the system[1]. The control goes to bootloader.
> The bootloader then checks RTC scratchpad registers to confirm it was an
> rtc_only wakeup and follows a different path, configure bare minimal
> clocks for ddr and then jumps to the resume address in another RTC
> scratchpad registers and transfers the control to Kernel. Kernel then
> restores the saved context. omap_rtc_power_off_program does the ALARM2
> programming part.
> 
>      [1] http://www.ti.com/lit/ug/spruhl7h/spruhl7h.pdf Page 2884
> 
> 2) Power-off: This is usual poweroff mode. omap_rtc_power_off calls the
> above omap_rtc_power_off_program function and in addition to that
> programs the OMAP_RTC_PMIC_REG for any external wake ups for PMIC like
> the pushbutton and shuts off the PMIC.
> 
> Hence the split in omap_rtc_power_off.
> 
> Signed-off-by: Keerthy <j-keerthy@ti.com>
> ---
>  drivers/rtc/rtc-omap.c | 53 ++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 38 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c
> index 88da927..cb19ece 100644
> --- a/drivers/rtc/rtc-omap.c
> +++ b/drivers/rtc/rtc-omap.c
> @@ -415,21 +415,12 @@ static int omap_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
>  
>  static struct omap_rtc *omap_rtc_power_off_rtc;
>  
> -/*
> - * omap_rtc_poweroff: RTC-controlled power off
> - *
> - * The RTC can be used to control an external PMIC via the pmic_power_en pin,
> - * which can be configured to transition to OFF on ALARM2 events.
> - *
> - * Notes:
> - * The two-second alarm offset is the shortest offset possible as the alarm
> - * registers must be set before the next timer update and the offset
> - * calculation is too heavy for everything to be done within a single access
> - * period (~15 us).
> - *
> - * Called with local interrupts disabled.
> +/**
> + * omap_rtc_power_off_program: Set the pmic power off sequence. The RTC
> + * generates pmic_pwr_enable control, which can be used to control an external
> + * PMIC.

Since this is kerneldoc, you need an empty line after "sequence." above.

You should also add a comment that this function depends on local
interrupts being disabled when called (for the wait_not_busy handling); 
and make sure you follow that in subsequent patches.

>   */
> -static void omap_rtc_power_off(void)
> +static int omap_rtc_power_off_program(struct device *dev)

dev is never used in this function.

>  {
>  	struct omap_rtc *rtc = omap_rtc_power_off_rtc;
>  	struct rtc_time tm;
> @@ -456,7 +447,7 @@ static void omap_rtc_power_off(void)
>  	if (tm2bcd(&tm) < 0) {
>  		dev_err(&rtc->rtc->dev, "power off failed\n");
>  		rtc->type->lock(rtc);
> -		return;
> +		return -EINVAL;
>  	}
>  
>  	rtc_wait_not_busy(rtc);
> @@ -481,6 +472,38 @@ static void omap_rtc_power_off(void)
>  		goto again;
>  	rtc->type->lock(rtc);
>  
> +	return 0;
> +}
> +
> +/*
> + * omap_rtc_poweroff: RTC-controlled power off
> + *
> + * The RTC can be used to control an external PMIC via the pmic_power_en pin,
> + * which can be configured to transition to OFF on ALARM2 events.
> + *
> + * Notes:
> + * The one-second alarm offset is the shortest offset possible as the alarm
> + * registers must be set before the next timer update and the offset
> + * calculation is too heavy for everything to be done within a single access
> + * period (~15 us).

This note really doesn't make much sense anymore, and should have been
updated as part of the previous patch.

> + *
> + * Called with local interrupts disabled.
> + */
> +static void omap_rtc_power_off(void)
> +{
> +	struct rtc_device *rtc = omap_rtc_power_off_rtc->rtc;

Use struct omap_rtc here as before.

> +	u32 val;
> +
> +	omap_rtc_power_off_program(rtc->dev.parent);
> +
> +	/* Set PMIC power enable and EXT_WAKEUP in case PB power on is used */
> +	omap_rtc_power_off_rtc->type->unlock(omap_rtc_power_off_rtc);
> +	val = rtc_readl(omap_rtc_power_off_rtc, OMAP_RTC_PMIC_REG);
> +	val |= OMAP_RTC_PMIC_POWER_EN_EN | OMAP_RTC_PMIC_EXT_WKUP_POL(0) |
> +			OMAP_RTC_PMIC_EXT_WKUP_EN(0);
> +	rtc_writel(omap_rtc_power_off_rtc, OMAP_RTC_PMIC_REG, val);
> +	omap_rtc_power_off_rtc->type->lock(omap_rtc_power_off_rtc);

What is all this, and why is it here?

Surely fiddling with this register after you've set the alarm to trigger
isn't the right thing to do.

> +
>  	/*
>  	 * Wait for alarm to trigger (within two seconds) and external PMIC to
>  	 * power off the system. Add a 500 ms margin for external latencies

Johan