Re: [PATCH v3 1/4] rtc: OMAP: Add support for rtc-only mode

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 03/04/2019 10:27:39+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>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
> 
> Changes in v3:
> 
>   * Exported out omap_rtc_power_off_program to rtc-omap header file
> 
>  drivers/rtc/rtc-omap.c       | 49 ++++++++++++++++++++++++++++++------
>  include/linux/rtc/rtc-omap.h |  7 ++++++
>  2 files changed, 48 insertions(+), 8 deletions(-)
>  create mode 100644 include/linux/rtc/rtc-omap.h
> 
> diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c
> index 32994b0dd139..a2941c875a06 100644
> --- a/drivers/rtc/rtc-omap.c
> +++ b/drivers/rtc/rtc-omap.c
> @@ -403,15 +403,12 @@ 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.
> - *
> - * 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.
>   */
> -static void omap_rtc_power_off(void)
> +int omap_rtc_power_off_program(struct device *dev)
>  {
>  	struct omap_rtc *rtc = omap_rtc_power_off_rtc;
>  	struct rtc_time tm;
> @@ -425,6 +422,9 @@ static void omap_rtc_power_off(void)
>  	rtc_writel(rtc, OMAP_RTC_PMIC_REG, val | OMAP_RTC_PMIC_POWER_EN_EN);
>  
>  again:
> +	/* Clear any existing ALARM2 event */
> +	rtc_writel(rtc, OMAP_RTC_STATUS_REG, OMAP_RTC_STATUS_ALARM2);
> +
>  	/* set alarm one second from now */
>  	omap_rtc_read_time_raw(rtc, &tm);
>  	seconds = tm.tm_sec;
> @@ -461,6 +461,39 @@ static void omap_rtc_power_off(void)
>  
>  	rtc->type->lock(rtc);
>  
> +	return 0;
> +}
> +EXPORT_SYMBOL(omap_rtc_power_off_program);
> +
> +/*
> + * 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).
> + *
> + * Called with local interrupts disabled.
> + */
> +static void omap_rtc_power_off(void)
> +{
> +	struct rtc_device *rtc = omap_rtc_power_off_rtc->rtc;
> +	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);
> +
>  	/*
>  	 * Wait for alarm to trigger (within one second) and external PMIC to
>  	 * power off the system. Add a 500 ms margin for external latencies
> diff --git a/include/linux/rtc/rtc-omap.h b/include/linux/rtc/rtc-omap.h
> new file mode 100644
> index 000000000000..9f03a329e63f
> --- /dev/null
> +++ b/include/linux/rtc/rtc-omap.h
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _LINUX_RTCOMAP_H_
> +#define _LINUX_RTCOMAP_H_
> +
> +int omap_rtc_power_off_program(struct device *dev);
> +#endif /* _LINUX_RTCOMAP_H_ */
> -- 
> 2.17.1
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com