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

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Message-ID: <78e5fbe5-9895-4467-af05-0aaf79820e06@oss.nxp.com>
Date: Wed, 12 Feb 2025 18:39:17 +0200
From: Ciprian Marian Costea <ciprianmarian.costea@....nxp.com>
To: Frank Li <Frank.li@....com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 NXP S32 Linux <s32@....com>, imx@...ts.linux.dev,
 Christophe Lizzi <clizzi@...hat.com>, Alberto Ruiz <aruizrui@...hat.com>,
 Enric Balletbo <eballetb@...hat.com>, Bogdan Hamciuc
 <bogdan.hamciuc@....com>, Ghennadi Procopciuc <Ghennadi.Procopciuc@....com>
Subject: Re: [PATCH v7 2/4] rtc: s32g: add NXP S32G2/S32G3 SoC support

On 2/12/2025 5:50 PM, Frank Li wrote:
> 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@....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@....com>
>>>>>> Signed-off-by: Bogdan Hamciuc <bogdan.hamciuc@....com>
>>>>>> Co-developed-by: Ghennadi Procopciuc <Ghennadi.Procopciuc@....com>
>>>>>> Signed-off-by: Ghennadi Procopciuc <Ghennadi.Procopciuc@....com>
>>>>>> Signed-off-by: Ciprian Marian Costea <ciprianmarian.costea@....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
> 

Sure. I will add such description on the resume path in V8.

Regards,
Ciprian

>>
>> 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
>>>>>>
>>>>
>>