Message-ID: <Z8HYUDy/XG+IYi9l@lizhi-Precision-Tower-5810>
Date: Fri, 28 Feb 2025 10:37:52 -0500
From: Frank Li <Frank.li@....com>
To: Ciprian Costea <ciprianmarian.costea@....nxp.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 v8 2/4] rtc: s32g: add NXP S32G2/S32G3 SoC support

On Fri, Feb 28, 2025 at 10:18:10AM +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>
> ---

Reviewed-by: Frank Li <Frank.Li@....com>

>  drivers/rtc/Kconfig    |  11 ++
>  drivers/rtc/Makefile   |   1 +
>  drivers/rtc/rtc-s32g.c | 386 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 398 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..251d86ab3046
> --- /dev/null
> +++ b/drivers/rtc/rtc-s32g.c
> @@ -0,0 +1,386 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright 2025 NXP
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/iopoll.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/rtc.h>
> +
> +#define RTCC_OFFSET	0x4ul
> +#define RTCS_OFFSET	0x8ul
> +#define APIVAL_OFFSET	0x10ul
> +
> +/* RTCC fields */
> +#define RTCC_CNTEN				BIT(31)
> +#define RTCC_APIEN				BIT(15)
> +#define RTCC_APIIE				BIT(14)
> +#define RTCC_CLKSEL_MASK		GENMASK(13, 12)
> +#define RTCC_DIV512EN			BIT(11)
> +#define RTCC_DIV32EN			BIT(10)
> +
> +/* RTCS fields */
> +#define RTCS_INV_API	BIT(17)
> +#define RTCS_APIF		BIT(13)
> +
> +#define APIVAL_MAX_VAL		GENMASK(31, 0)
> +#define RTC_SYNCH_TIMEOUT	(100 * USEC_PER_MSEC)
> +
> +/*
> + * S32G2 and S32G3 SoCs have RTC clock source1 reserved and
> + * should not be used.
> + */
> +#define RTC_CLK_SRC1_RESERVED		BIT(1)
> +
> +/*
> + * S32G RTC module has a 512 value and a 32 value hardware frequency
> + * divisors (DIV512 and DIV32) which could be used to achieve higher
> + * counter ranges by lowering the RTC frequency.
> + */
> +enum {
> +	DIV1 = 1,
> +	DIV32 = 32,
> +	DIV512 = 512,
> +	DIV512_32 = 16384
> +};
> +
> +static const char *const rtc_clk_src[] = {
> +	"source0",
> +	"source1",
> +	"source2",
> +	"source3"
> +};
> +
> +struct rtc_priv {
> +	struct rtc_device *rdev;
> +	void __iomem *rtc_base;
> +	struct clk *ipg;
> +	struct clk *clk_src;
> +	const struct rtc_soc_data *rtc_data;
> +	u64 rtc_hz;
> +	time64_t sleep_sec;
> +	int irq;
> +	u32 clk_src_idx;
> +};
> +
> +struct rtc_soc_data {
> +	u32 clk_div;
> +	u32 reserved_clk_mask;
> +};
> +
> +static const struct rtc_soc_data rtc_s32g2_data = {
> +	.clk_div = DIV512_32,
> +	.reserved_clk_mask = RTC_CLK_SRC1_RESERVED,
> +};
> +
> +static irqreturn_t s32g_rtc_handler(int irq, void *dev)
> +{
> +	struct rtc_priv *priv = platform_get_drvdata(dev);
> +	u32 status;
> +
> +	status = readl(priv->rtc_base + RTCS_OFFSET);
> +
> +	if (status & RTCS_APIF) {
> +		writel(0x0, priv->rtc_base + APIVAL_OFFSET);
> +		writel(status | RTCS_APIF, priv->rtc_base + RTCS_OFFSET);
> +	}
> +
> +	rtc_update_irq(priv->rdev, 1, RTC_IRQF | RTC_AF);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/*
> + * The function is not really getting time from the RTC since the S32G RTC
> + * has several limitations. Thus, to setup alarm use system time.
> + */
> +static int s32g_rtc_read_time(struct device *dev,
> +			      struct rtc_time *tm)
> +{
> +	struct rtc_priv *priv = dev_get_drvdata(dev);
> +	time64_t sec;
> +
> +	if (check_add_overflow(ktime_get_real_seconds(),
> +			       priv->sleep_sec, &sec))
> +		return -ERANGE;
> +
> +	rtc_time64_to_tm(sec, tm);
> +
> +	return 0;
> +}
> +
> +static int s32g_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct rtc_priv *priv = dev_get_drvdata(dev);
> +	u32 rtcc, rtcs;
> +
> +	rtcc = readl(priv->rtc_base + RTCC_OFFSET);
> +	rtcs = readl(priv->rtc_base + RTCS_OFFSET);
> +
> +	alrm->enabled = rtcc & RTCC_APIIE;
> +	if (alrm->enabled)
> +		alrm->pending = !(rtcs & RTCS_APIF);
> +
> +	return 0;
> +}
> +
> +static int s32g_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
> +{
> +	struct rtc_priv *priv = dev_get_drvdata(dev);
> +	u32 rtcc;
> +
> +	/* RTC API functionality is used both for triggering interrupts
> +	 * and as a wakeup event. Hence it should always be enabled.
> +	 */
> +	rtcc = readl(priv->rtc_base + RTCC_OFFSET);
> +	rtcc |= RTCC_APIEN | RTCC_APIIE;
> +	writel(rtcc, priv->rtc_base + RTCC_OFFSET);
> +
> +	return 0;
> +}
> +
> +static int s32g_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct rtc_priv *priv = dev_get_drvdata(dev);
> +	unsigned long long cycles;
> +	long long t_offset;
> +	time64_t alrm_time;
> +	u32 rtcs;
> +	int ret;
> +
> +	alrm_time = rtc_tm_to_time64(&alrm->time);
> +	t_offset = alrm_time - ktime_get_real_seconds() - priv->sleep_sec;
> +	if (t_offset < 0)
> +		return -ERANGE;
> +
> +	cycles = t_offset * priv->rtc_hz;
> +	if (cycles > APIVAL_MAX_VAL)
> +		return -ERANGE;
> +
> +	/* APIVAL could have been reset from the IRQ handler.
> +	 * Hence, we wait in case there is a synchronization process.
> +	 */
> +	ret = read_poll_timeout(readl, rtcs, !(rtcs & RTCS_INV_API),
> +				0, RTC_SYNCH_TIMEOUT, false, priv->rtc_base + RTCS_OFFSET);
> +	if (ret)
> +		return ret;
> +
> +	writel(cycles, priv->rtc_base + APIVAL_OFFSET);
> +
> +	return read_poll_timeout(readl, rtcs, !(rtcs & RTCS_INV_API),
> +				0, RTC_SYNCH_TIMEOUT, false, priv->rtc_base + RTCS_OFFSET);
> +}
> +
> +/*
> + * Disable the 32-bit free running counter.
> + * This allows Clock Source and Divisors selection
> + * to be performed without causing synchronization issues.
> + */
> +static void s32g_rtc_disable(struct rtc_priv *priv)
> +{
> +	u32 rtcc = readl(priv->rtc_base + RTCC_OFFSET);
> +
> +	rtcc &= ~RTCC_CNTEN;
> +	writel(rtcc, priv->rtc_base + RTCC_OFFSET);
> +}
> +
> +static void s32g_rtc_enable(struct rtc_priv *priv)
> +{
> +	u32 rtcc = readl(priv->rtc_base + RTCC_OFFSET);
> +
> +	rtcc |= RTCC_CNTEN;
> +	writel(rtcc, priv->rtc_base + RTCC_OFFSET);
> +}
> +
> +static int rtc_clk_src_setup(struct rtc_priv *priv)
> +{
> +	u32 rtcc;
> +
> +	if (priv->rtc_data->reserved_clk_mask & (1 << priv->clk_src_idx))
> +		return -EOPNOTSUPP;
> +
> +	rtcc = FIELD_PREP(RTCC_CLKSEL_MASK, priv->clk_src_idx);
> +
> +	switch (priv->rtc_data->clk_div) {
> +	case DIV512_32:
> +		rtcc |= RTCC_DIV512EN;
> +		rtcc |= RTCC_DIV32EN;
> +		break;
> +	case DIV512:
> +		rtcc |= RTCC_DIV512EN;
> +		break;
> +	case DIV32:
> +		rtcc |= RTCC_DIV32EN;
> +		break;
> +	case DIV1:
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	rtcc |= RTCC_APIEN | RTCC_APIIE;
> +	/*
> +	 * Make sure the CNTEN is 0 before we configure
> +	 * the clock source and dividers.
> +	 */
> +	s32g_rtc_disable(priv);
> +	writel(rtcc, priv->rtc_base + RTCC_OFFSET);
> +	s32g_rtc_enable(priv);
> +
> +	return 0;
> +}
> +
> +static const struct rtc_class_ops rtc_ops = {
> +	.read_time = s32g_rtc_read_time,
> +	.read_alarm = s32g_rtc_read_alarm,
> +	.set_alarm = s32g_rtc_set_alarm,
> +	.alarm_irq_enable = s32g_rtc_alarm_irq_enable,
> +};
> +
> +static int rtc_clk_dts_setup(struct rtc_priv *priv,
> +			     struct device *dev)
> +{
> +	u32 i;
> +
> +	priv->ipg = devm_clk_get_enabled(dev, "ipg");
> +	if (IS_ERR(priv->ipg))
> +		return dev_err_probe(dev, PTR_ERR(priv->ipg),
> +				"Failed to get 'ipg' clock\n");
> +
> +	for (i = 0; i < ARRAY_SIZE(rtc_clk_src); i++) {
> +		priv->clk_src = devm_clk_get_enabled(dev, rtc_clk_src[i]);
> +		if (!IS_ERR(priv->clk_src)) {
> +			priv->clk_src_idx = i;
> +			break;
> +		}
> +	}
> +
> +	if (IS_ERR(priv->clk_src))
> +		return dev_err_probe(dev, PTR_ERR(priv->clk_src),
> +				"Failed to get rtc module clock source\n");
> +
> +	return 0;
> +}
> +
> +static int s32g_rtc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct rtc_priv *priv;
> +	unsigned long rtc_hz;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->rtc_data = of_device_get_match_data(dev);
> +	if (!priv->rtc_data)
> +		return -ENODEV;
> +
> +	priv->rtc_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(priv->rtc_base))
> +		return PTR_ERR(priv->rtc_base);
> +
> +	device_init_wakeup(dev, true);
> +
> +	ret = rtc_clk_dts_setup(priv, dev);
> +	if (ret)
> +		return ret;
> +
> +	priv->rdev = devm_rtc_allocate_device(dev);
> +	if (IS_ERR(priv->rdev))
> +		return PTR_ERR(priv->rdev);
> +
> +	ret = rtc_clk_src_setup(priv);
> +	if (ret)
> +		return ret;
> +
> +	priv->irq = platform_get_irq(pdev, 0);
> +	if (priv->irq < 0) {
> +		ret = priv->irq;
> +		goto disable_rtc;
> +	}
> +
> +	rtc_hz = clk_get_rate(priv->clk_src);
> +	if (!rtc_hz) {
> +		dev_err(dev, "Failed to get RTC frequency\n");
> +		ret = -EINVAL;
> +		goto disable_rtc;
> +	}
> +
> +	priv->rtc_hz = rtc_hz / priv->rtc_data->clk_div;
> +	if (rtc_hz % priv->rtc_data->clk_div)
> +		priv->rtc_hz++;
> +
> +	platform_set_drvdata(pdev, priv);
> +	priv->rdev->ops = &rtc_ops;
> +
> +	ret = devm_request_irq(dev, priv->irq,
> +			       s32g_rtc_handler, 0, dev_name(dev), pdev);
> +	if (ret) {
> +		dev_err(dev, "Request interrupt %d failed, error: %d\n",
> +			priv->irq, ret);
> +		goto disable_rtc;
> +	}
> +
> +	ret = devm_rtc_register_device(priv->rdev);
> +	if (ret)
> +		goto disable_rtc;
> +
> +	return 0;
> +
> +disable_rtc:
> +	s32g_rtc_disable(priv);
> +	return ret;
> +}
> +
> +static int s32g_rtc_suspend(struct device *dev)
> +{
> +	struct rtc_priv *priv = dev_get_drvdata(dev);
> +	u32 apival = readl(priv->rtc_base + APIVAL_OFFSET);
> +
> +	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;
> +	}
> +
> +	return 0;
> +}
> +
> +static int s32g_rtc_resume(struct device *dev)
> +{
> +	struct rtc_priv *priv = dev_get_drvdata(dev);
> +
> +	/* The transition from resume to run is a reset event.
> +	 * This leads to the RTC registers being reset after resume from
> +	 * suspend. It is uncommon, but this behaviour has been observed
> +	 * on S32G RTC after issueing a Suspend to RAM operation.
> +	 * Thus, reconfigure RTC registers on the resume path.
> +	 */
> +	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
>

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