Re: [PATCH v7 2/4] rtc: s32g: add NXP S32G2/S32G3 SoC support

[Frank Li <Frank.li@nxp.com>]

On Wed, Feb 12, 2025 at 10:11:35AM +0200, Ciprian Marian Costea wrote:
> On 2/11/2025 7:07 PM, Frank Li wrote:
> > On Tue, Feb 11, 2025 at 01:25:38PM +0200, Ciprian Marian Costea wrote:
> > > On 2/7/2025 10:16 PM, Frank Li wrote:
> > > > On Fri, Feb 07, 2025 at 06:38:06PM +0200, Ciprian Costea wrote:
> > > > > From: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
> > > > >
> > > > > Add a RTC driver for NXP S32G2/S32G3 SoCs.
> > > > >
> > > > > RTC tracks clock time during system suspend. It can be a wakeup source
> > > > > for the S32G2/S32G3 SoC based boards.
> > > > >
> > > > > The RTC module from S32G2/S32G3 is not battery-powered and it is not kept
> > > > > alive during system reset.
> > > > >
> > > > > Co-developed-by: Bogdan Hamciuc <bogdan.hamciuc@nxp.com>
> > > > > Signed-off-by: Bogdan Hamciuc <bogdan.hamciuc@nxp.com>
> > > > > Co-developed-by: Ghennadi Procopciuc <Ghennadi.Procopciuc@nxp.com>
> > > > > Signed-off-by: Ghennadi Procopciuc <Ghennadi.Procopciuc@nxp.com>
> > > > > Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@oss.nxp.com>
> > > > > ---
> > > > >    drivers/rtc/Kconfig    |  11 ++
> > > > >    drivers/rtc/Makefile   |   1 +
> > > > >    drivers/rtc/rtc-s32g.c | 383 +++++++++++++++++++++++++++++++++++++++++
> > > > >    3 files changed, 395 insertions(+)
> > > > >    create mode 100644 drivers/rtc/rtc-s32g.c
> > > > >
> > > > > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > > > > index 0bbbf778ecfa..510dc2db745d 100644
> > > > > --- a/drivers/rtc/Kconfig
> > > > > +++ b/drivers/rtc/Kconfig
> > > > > @@ -2103,4 +2103,15 @@ config RTC_DRV_AMLOGIC_A4
> > > > >    	  This driver can also be built as a module. If so, the module
> > > > >    	  will be called "rtc-amlogic-a4".
> > > > >
> > > > > +config RTC_DRV_S32G
> > > > > +	tristate "RTC driver for S32G2/S32G3 SoCs"
> > > > > +	depends on ARCH_S32 || COMPILE_TEST
> > > > > +	depends on COMMON_CLK
> > > > > +	help
> > > > > +	  Say yes to enable RTC driver for platforms based on the
> > > > > +	  S32G2/S32G3 SoC family.
> > > > > +
> > > > > +	  This RTC module can be used as a wakeup source.
> > > > > +	  Please note that it is not battery-powered.
> > > > > +
> > > > >    endif # RTC_CLASS
> > > > > diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> > > > > index 489b4ab07068..e4b616ecd5ce 100644
> > > > > --- a/drivers/rtc/Makefile
> > > > > +++ b/drivers/rtc/Makefile
> > > > > @@ -161,6 +161,7 @@ obj-$(CONFIG_RTC_DRV_RX8111)	+= rtc-rx8111.o
> > > > >    obj-$(CONFIG_RTC_DRV_RX8581)	+= rtc-rx8581.o
> > > > >    obj-$(CONFIG_RTC_DRV_RZN1)	+= rtc-rzn1.o
> > > > >    obj-$(CONFIG_RTC_DRV_RENESAS_RTCA3)	+= rtc-renesas-rtca3.o
> > > > > +obj-$(CONFIG_RTC_DRV_S32G)	+= rtc-s32g.o
> > > > >    obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
> > > > >    obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
> > > > >    obj-$(CONFIG_RTC_DRV_S5M)	+= rtc-s5m.o
> > > > > diff --git a/drivers/rtc/rtc-s32g.c b/drivers/rtc/rtc-s32g.c
> > > > > new file mode 100644
> > > > > index 000000000000..3244b23c533e
> > > > > --- /dev/null
> > > > > +++ b/drivers/rtc/rtc-s32g.c
> > > >
> > > > ...
> > > >
> > > > > +
> > > > > +static int s32g_rtc_suspend(struct device *dev)
> > > > > +{
> > > > > +	struct rtc_priv *priv = dev_get_drvdata(dev);
> > > > > +	u32 apival = readl(priv->rtc_base + APIVAL_OFFSET);
> > > > > +
> > > > > +	/* RTC registers are being reset in suspend.
> > > > > +	 * Thus store standby time.
> > > > > +	 */
> > > > > +	if (check_add_overflow(priv->sleep_sec, div64_u64(apival, priv->rtc_hz),
> > > > > +			       &priv->sleep_sec)) {
> > > > > +		dev_warn(dev, "Overflow on sleep cycles occurred. Resetting to 0.\n");
> > > > > +		priv->sleep_sec = 0;
> > > > > +	}
> > > >
> > > > Strange. If RTC register are reset in suspend. How do it wake up system?
> > > >
> > > > Frank
> > > >
> > >
> > > Hello Frank,
> > >
> > > I believe the transition between resume to run is a reset event. This would
> > > lead to the RTC registers being reset after resume from suspend (triggered
> > > via Suspend to RAM).
> >
> > It is weird design. I suppose it should be design error. (any errata for
> > it).
> >
> > Frank
> >
>
> Unfortunately I could not find any such errata. But this behaviour (RTC
> registers being reset) is what I see when resuming from Suspend to RAM
> operations.

Okay, it worth add comment here to descript hardware behaviour, which is
actually uncommon.

Frank

>
> Regards,
> Ciprian
>
> > >
> > > On the other hand, the RTC is kept on during suspend for as long as its been
> > > set up (for example via rtcwake -s), thus waking up the sistem via an API
> > > interrupt.
> > >
> > > Regards,
> > > Ciprian
> > >
> > > > > +
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int s32g_rtc_resume(struct device *dev)
> > > > > +{
> > > > > +	struct rtc_priv *priv = dev_get_drvdata(dev);
> > > > > +
> > > > > +	return rtc_clk_src_setup(priv);
> > > > > +}
> > > > > +
> > > > > +static const struct of_device_id rtc_dt_ids[] = {
> > > > > +	{ .compatible = "nxp,s32g2-rtc", .data = &rtc_s32g2_data},
> > > > > +	{ /* sentinel */ },
> > > > > +};
> > > > > +
> > > > > +static DEFINE_SIMPLE_DEV_PM_OPS(s32g_rtc_pm_ops,
> > > > > +			 s32g_rtc_suspend, s32g_rtc_resume);
> > > > > +
> > > > > +static struct platform_driver s32g_rtc_driver = {
> > > > > +	.driver		= {
> > > > > +		.name			= "s32g-rtc",
> > > > > +		.pm				= pm_sleep_ptr(&s32g_rtc_pm_ops),
> > > > > +		.of_match_table = rtc_dt_ids,
> > > > > +	},
> > > > > +	.probe		= s32g_rtc_probe,
> > > > > +};
> > > > > +module_platform_driver(s32g_rtc_driver);
> > > > > +
> > > > > +MODULE_AUTHOR("NXP");
> > > > > +MODULE_DESCRIPTION("NXP RTC driver for S32G2/S32G3");
> > > > > +MODULE_LICENSE("GPL");
> > > > > --
> > > > > 2.45.2
> > > > >
> > >
>