Re: [PATCH] rtc: ti-k3: Add support to resume from IO DDR low power mode

[Vignesh Raghavendra <vigneshr@ti.com>]

On 11/03/26 12:32, Akashdeep Kaur wrote:
> During IO DDR low power mode, the RTC IP is reset and loses its
> register configuration. 

> The DDR memory still preserves all driver states
> (reference counts, software context). 

That's the definition of Suspend to RAM

> System clocks are saved and restored
> by Device Manager (DM) firmware during the resume sequence.

Not relevant for this patch in particular.

> Add support to reconfigure the RTC IP registers in resume handler only if
> resume hook is called during IO DDR low power mode resume.
> 

Above all is probably bit too verbose. Below text is all thats needed:

Restore the RTC HW context which may be lost when system enters certain
low power mode (IO+DDR mode). Check if the RTC registers are locked
which would indicate loss of context (reset) and restore the context as
needed.

> Signed-off-by: Akashdeep Kaur <a-kaur@ti.com>
> ---
> 
> Tested deep sleep with rtcwake after IO DDR resume on AM62P-SK.
> 
> ---
>  drivers/rtc/rtc-ti-k3.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-ti-k3.c b/drivers/rtc/rtc-ti-k3.c
> index ec759d8f7023..e801f5b9d757 100644
> --- a/drivers/rtc/rtc-ti-k3.c
> +++ b/drivers/rtc/rtc-ti-k3.c
> @@ -640,10 +640,18 @@ static int __maybe_unused ti_k3_rtc_suspend(struct device *dev)
>  static int __maybe_unused ti_k3_rtc_resume(struct device *dev)
>  {
>  	struct ti_k3_rtc *priv = dev_get_drvdata(dev);
> +	int ret = 0;
> +
> +	if (k3rtc_check_unlocked(priv)) {
> +		/* RTC locked implies low power mode exit where RTC loses context */
> +		ret = k3rtc_configure(dev);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	if (device_may_wakeup(dev))
>  		disable_irq_wake(priv->irq);
> -	return 0;
> +	return ret;
>  }
>  
>  static SIMPLE_DEV_PM_OPS(ti_k3_rtc_pm_ops, ti_k3_rtc_suspend, ti_k3_rtc_resume);

-- 
Regards
Vignesh
https://ti.com/opensource