Re: [rtc-linux] [PATCH] rtc: OMAP: Add external 32k clock feature

[Keerthy]

Hi Andrew,

Apologies for replying late.

On Wednesday 25 March 2015 04:29 AM, Andrew Morton wrote:
> On Tue, 3 Mar 2015 15:12:02 +0530 Keerthy <j-keerthy@xxxxxx> wrote:
>
> > Add external 32k clock feature. The internal clock will be gated during suspend.
> > Hence make use of the external 32k clock so that rtc is functional accross
> > suspend/resume.
> >
> > ...
> >
> > @@ -446,6 +449,7 @@ static const struct omap_rtc_device_type omap_rtc_default_type = {
> >
> >   static const struct omap_rtc_device_type omap_rtc_am3352_type = {
> >   	.has_32kclk_en	= true,
> > +	.has_osc_ext_32k = true,
> >   	.has_kicker	= true,
> >   	.has_irqwakeen	= true,
> >   	.has_pmic_mode	= true,
> > @@ -543,7 +547,16 @@ static int __init omap_rtc_probe(struct platform_device *pdev)
> >   	if (rtc->type->has_32kclk_en) {
> >   		reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
> >   		rtc_writel(rtc, OMAP_RTC_OSC_REG,
> > -				reg | OMAP_RTC_OSC_32KCLK_EN);
> > +			   reg | OMAP_RTC_OSC_32KCLK_EN);
> > +	}
> > +
> > +	/* Enable External clock as the source */
> > +
> > +	if (rtc->type->has_osc_ext_32k) {
> > +		rtc_writel(rtc, OMAP_RTC_OSC_REG,
> > +			   (OMAP_RTC_OSC_EXT_32K |
> > +			   rtc_read(rtc, OMAP_RTC_OSC_REG)) &
> > +			   (~OMAP_RTC_OSC_OSC32K_GZ));
> >   	}
>
> How do we know that all systems have this external clock and that it
> works OK?

AM335 and AM43X have the external clock feature which we choose using 
RTC_OSC_REG. I verified it works OK by seeing the RTC seconds ticking 
even after switching the source to the external 32k Clock.

Regards,
Keerthy
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