Message-ID: <aJtZl3jgBD0hLyt0@lizhi-Precision-Tower-5810>
Date: Tue, 12 Aug 2025 11:11:19 -0400
From: Frank Li <Frank.li@....com>
To: Wei Fang <wei.fang@....com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	richardcochran@...il.com, claudiu.manoil@....com,
	vladimir.oltean@....com, xiaoning.wang@....com,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, vadim.fedorenko@...ux.dev,
	shawnguo@...nel.org, s.hauer@...gutronix.de, festevam@...il.com,
	fushi.peng@....com, devicetree@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev, kernel@...gutronix.de
Subject: Re: [PATCH v3 net-next 05/15] ptp: netc: add PTP_CLK_REQ_PPS support

On Tue, Aug 12, 2025 at 05:46:24PM +0800, Wei Fang wrote:
> The NETC Timer is capable of generating a PPS interrupt to the host. To
> support this feature, a 64-bit alarm time (which is a integral second
> of PHC in the future) is set to TMR_ALARM, and the period is set to
> TMR_FIPER. The alarm time is compared to the current time on each update,
> then the alarm trigger is used as an indication to the TMR_FIPER starts
> down counting. After the period has passed, the PPS event is generated.
>
> According to the NETC block guide, the Timer has three FIPERs, any of
> which can be used to generate the PPS events, but in the current
> implementation, we only need one of them to implement the PPS feature,
> so FIPER 0 is used as the default PPS generator. Also, the Timer has
> 2 ALARMs, currently, ALARM 0 is used as the default time comparator.
>
> However, if there is a time drift when PPS is enabled, the PPS event will
> not be generated at an integral second of PHC. The suggested steps from
> IP team if time drift happens:

according to patch, "drift" means timer adjust period?
netc_timer_adjust_period()

generally, netc_timer_adjust_period() happen 4 times every second, does
disable/re-enable impact pps accurate?

Frank
>
> 1. Disable FIPER before adjusting the hardware time
> 2. Rearm ALARM after the time adjustment to make the next PPS event be
> generated at an integral second of PHC.
> 3. Re-enable FIPER.
>
> Signed-off-by: Wei Fang <wei.fang@....com>
>
> ---
> v2 changes:
> 1. Refine the subject and the commit message
> 2. Add a comment to netc_timer_enable_pps()
> 3. Remove the "nxp,pps-channel" logic from the driver
> v3 changes:
> 1. Use "2 * NSEC_PER_SEC" to instead of "2000000000U"
> 2. Improve the commit message
> 3. Add alarm related logic and the irq handler
> 4. Add tmr_emask to struct netc_timer to save the irq masks instead of
>    reading TMR_EMASK register
> 5. Remove pps_channel from struct netc_timer and remove
>    NETC_TMR_DEFAULT_PPS_CHANNEL
> ---
>  drivers/ptp/ptp_netc.c | 260 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 257 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/ptp/ptp_netc.c b/drivers/ptp/ptp_netc.c
> index cbe2a64d1ced..9026a967a5fe 100644
> --- a/drivers/ptp/ptp_netc.c
> +++ b/drivers/ptp/ptp_netc.c
> @@ -20,7 +20,14 @@
>  #define  TMR_CTRL_TE			BIT(2)
>  #define  TMR_COMP_MODE			BIT(15)
>  #define  TMR_CTRL_TCLK_PERIOD		GENMASK(25, 16)
> +#define  TMR_CTRL_FS			BIT(28)
>
> +#define NETC_TMR_TEVENT			0x0084
> +#define  TMR_TEVNET_PPEN(i)		BIT(7 - (i))
> +#define  TMR_TEVENT_PPEN_ALL		GENMASK(7, 5)
> +#define  TMR_TEVENT_ALMEN(i)		BIT(16 + (i))
> +
> +#define NETC_TMR_TEMASK			0x0088
>  #define NETC_TMR_CNT_L			0x0098
>  #define NETC_TMR_CNT_H			0x009c
>  #define NETC_TMR_ADD			0x00a0
> @@ -28,9 +35,19 @@
>  #define NETC_TMR_OFF_L			0x00b0
>  #define NETC_TMR_OFF_H			0x00b4
>
> +/* i = 0, 1, i indicates the index of TMR_ALARM */
> +#define NETC_TMR_ALARM_L(i)		(0x00b8 + (i) * 8)
> +#define NETC_TMR_ALARM_H(i)		(0x00bc + (i) * 8)
> +
> +/* i = 0, 1, 2. i indicates the index of TMR_FIPER. */
> +#define NETC_TMR_FIPER(i)		(0x00d0 + (i) * 4)
> +
>  #define NETC_TMR_FIPER_CTRL		0x00dc
>  #define  FIPER_CTRL_DIS(i)		(BIT(7) << (i) * 8)
>  #define  FIPER_CTRL_PG(i)		(BIT(6) << (i) * 8)
> +#define  FIPER_CTRL_FS_ALARM(i)		(BIT(5) << (i) * 8)
> +#define  FIPER_CTRL_PW(i)		(GENMASK(4, 0) << (i) * 8)
> +#define  FIPER_CTRL_SET_PW(i, v)	(((v) & GENMASK(4, 0)) << 8 * (i))
>
>  #define NETC_TMR_CUR_TIME_L		0x00f0
>  #define NETC_TMR_CUR_TIME_H		0x00f4
> @@ -39,6 +56,9 @@
>
>  #define NETC_TMR_FIPER_NUM		3
>  #define NETC_TMR_DEFAULT_PRSC		2
> +#define NETC_TMR_DEFAULT_ALARM		GENMASK_ULL(63, 0)
> +#define NETC_TMR_DEFAULT_FIPER		GENMASK(31, 0)
> +#define NETC_TMR_FIPER_MAX_PW		GENMASK(4, 0)
>
>  /* 1588 timer reference clock source select */
>  #define NETC_TMR_CCM_TIMER1		0 /* enet_timer1_clk_root, from CCM */
> @@ -60,6 +80,10 @@ struct netc_timer {
>  	u32 oclk_prsc;
>  	/* High 32-bit is integer part, low 32-bit is fractional part */
>  	u64 period;
> +
> +	int irq;
> +	u32 tmr_emask;
> +	bool pps_enabled;
>  };
>
>  #define netc_timer_rd(p, o)		netc_read((p)->base + (o))
> @@ -124,6 +148,155 @@ static u64 netc_timer_cur_time_read(struct netc_timer *priv)
>  	return ns;
>  }
>
> +static void netc_timer_alarm_write(struct netc_timer *priv,
> +				   u64 alarm, int index)
> +{
> +	u32 alarm_h = upper_32_bits(alarm);
> +	u32 alarm_l = lower_32_bits(alarm);
> +
> +	netc_timer_wr(priv, NETC_TMR_ALARM_L(index), alarm_l);
> +	netc_timer_wr(priv, NETC_TMR_ALARM_H(index), alarm_h);
> +}
> +
> +static u32 netc_timer_get_integral_period(struct netc_timer *priv)
> +{
> +	u32 tmr_ctrl, integral_period;
> +
> +	tmr_ctrl = netc_timer_rd(priv, NETC_TMR_CTRL);
> +	integral_period = FIELD_GET(TMR_CTRL_TCLK_PERIOD, tmr_ctrl);
> +
> +	return integral_period;
> +}
> +
> +static u32 netc_timer_calculate_fiper_pw(struct netc_timer *priv,
> +					 u32 fiper)
> +{
> +	u64 divisor, pulse_width;
> +
> +	/* Set the FIPER pulse width to half FIPER interval by default.
> +	 * pulse_width = (fiper / 2) / TMR_GCLK_period,
> +	 * TMR_GCLK_period = NSEC_PER_SEC / TMR_GCLK_freq,
> +	 * TMR_GCLK_freq = (clk_freq / oclk_prsc) Hz,
> +	 * so pulse_width = fiper * clk_freq / (2 * NSEC_PER_SEC * oclk_prsc).
> +	 */
> +	divisor = mul_u32_u32(2 * NSEC_PER_SEC, priv->oclk_prsc);
> +	pulse_width = div64_u64(mul_u32_u32(fiper, priv->clk_freq), divisor);
> +
> +	/* The FIPER_PW field only has 5 bits, need to update oclk_prsc */
> +	if (pulse_width > NETC_TMR_FIPER_MAX_PW)
> +		pulse_width = NETC_TMR_FIPER_MAX_PW;
> +
> +	return pulse_width;
> +}
> +
> +static void netc_timer_set_pps_alarm(struct netc_timer *priv, int channel,
> +				     u32 integral_period)
> +{
> +	u64 alarm;
> +
> +	/* Get the alarm value */
> +	alarm = netc_timer_cur_time_read(priv) +  NSEC_PER_MSEC;
> +	alarm = roundup_u64(alarm, NSEC_PER_SEC);
> +	alarm = roundup_u64(alarm, integral_period);
> +
> +	netc_timer_alarm_write(priv, alarm, 0);
> +}
> +
> +/* Note that users should not use this API to output PPS signal on
> + * external pins, because PTP_CLK_REQ_PPS trigger internal PPS event
> + * for input into kernel PPS subsystem. See:
> + * https://lore.kernel.org/r/20201117213826.18235-1-a.fatoum@pengutronix.de
> + */
> +static int netc_timer_enable_pps(struct netc_timer *priv,
> +				 struct ptp_clock_request *rq, int on)
> +{
> +	u32 fiper, fiper_ctrl;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&priv->lock, flags);
> +
> +	fiper_ctrl = netc_timer_rd(priv, NETC_TMR_FIPER_CTRL);
> +
> +	if (on) {
> +		u32 integral_period, fiper_pw;
> +
> +		if (priv->pps_enabled)
> +			goto unlock_spinlock;
> +
> +		integral_period = netc_timer_get_integral_period(priv);
> +		fiper = NSEC_PER_SEC - integral_period;
> +		fiper_pw = netc_timer_calculate_fiper_pw(priv, fiper);
> +		fiper_ctrl &= ~(FIPER_CTRL_DIS(0) | FIPER_CTRL_PW(0) |
> +				FIPER_CTRL_FS_ALARM(0));
> +		fiper_ctrl |= FIPER_CTRL_SET_PW(0, fiper_pw);
> +		priv->tmr_emask |= TMR_TEVNET_PPEN(0) | TMR_TEVENT_ALMEN(0);
> +		priv->pps_enabled = true;
> +		netc_timer_set_pps_alarm(priv, 0, integral_period);
> +	} else {
> +		if (!priv->pps_enabled)
> +			goto unlock_spinlock;
> +
> +		fiper = NETC_TMR_DEFAULT_FIPER;
> +		priv->tmr_emask &= ~(TMR_TEVNET_PPEN(0) |
> +				     TMR_TEVENT_ALMEN(0));
> +		fiper_ctrl |= FIPER_CTRL_DIS(0);
> +		priv->pps_enabled = false;
> +		netc_timer_alarm_write(priv, NETC_TMR_DEFAULT_ALARM, 0);
> +	}
> +
> +	netc_timer_wr(priv, NETC_TMR_TEMASK, priv->tmr_emask);
> +	netc_timer_wr(priv, NETC_TMR_FIPER(0), fiper);
> +	netc_timer_wr(priv, NETC_TMR_FIPER_CTRL, fiper_ctrl);
> +
> +unlock_spinlock:
> +	spin_unlock_irqrestore(&priv->lock, flags);
> +
> +	return 0;
> +}
> +
> +static void netc_timer_disable_pps_fiper(struct netc_timer *priv)
> +{
> +	u32 fiper_ctrl;
> +
> +	if (!priv->pps_enabled)
> +		return;
> +
> +	fiper_ctrl = netc_timer_rd(priv, NETC_TMR_FIPER_CTRL);
> +	fiper_ctrl |= FIPER_CTRL_DIS(0);
> +	netc_timer_wr(priv, NETC_TMR_FIPER(0), NETC_TMR_DEFAULT_FIPER);
> +	netc_timer_wr(priv, NETC_TMR_FIPER_CTRL, fiper_ctrl);
> +}
> +
> +static void netc_timer_enable_pps_fiper(struct netc_timer *priv)
> +{
> +	u32 fiper_ctrl, integral_period, fiper;
> +
> +	if (!priv->pps_enabled)
> +		return;
> +
> +	integral_period = netc_timer_get_integral_period(priv);
> +	fiper_ctrl = netc_timer_rd(priv, NETC_TMR_FIPER_CTRL);
> +	fiper_ctrl &= ~FIPER_CTRL_DIS(0);
> +	fiper = NSEC_PER_SEC - integral_period;
> +
> +	netc_timer_set_pps_alarm(priv, 0, integral_period);
> +	netc_timer_wr(priv, NETC_TMR_FIPER(0), fiper);
> +	netc_timer_wr(priv, NETC_TMR_FIPER_CTRL, fiper_ctrl);
> +}
> +
> +static int netc_timer_enable(struct ptp_clock_info *ptp,
> +			     struct ptp_clock_request *rq, int on)
> +{
> +	struct netc_timer *priv = ptp_to_netc_timer(ptp);
> +
> +	switch (rq->type) {
> +	case PTP_CLK_REQ_PPS:
> +		return netc_timer_enable_pps(priv, rq, on);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
>  static void netc_timer_adjust_period(struct netc_timer *priv, u64 period)
>  {
>  	u32 fractional_period = lower_32_bits(period);
> @@ -136,8 +309,11 @@ static void netc_timer_adjust_period(struct netc_timer *priv, u64 period)
>  	old_tmr_ctrl = netc_timer_rd(priv, NETC_TMR_CTRL);
>  	tmr_ctrl = u32_replace_bits(old_tmr_ctrl, integral_period,
>  				    TMR_CTRL_TCLK_PERIOD);
> -	if (tmr_ctrl != old_tmr_ctrl)
> +	if (tmr_ctrl != old_tmr_ctrl) {
> +		netc_timer_disable_pps_fiper(priv);
>  		netc_timer_wr(priv, NETC_TMR_CTRL, tmr_ctrl);
> +		netc_timer_enable_pps_fiper(priv);
> +	}
>
>  	netc_timer_wr(priv, NETC_TMR_ADD, fractional_period);
>
> @@ -163,6 +339,8 @@ static int netc_timer_adjtime(struct ptp_clock_info *ptp, s64 delta)
>
>  	spin_lock_irqsave(&priv->lock, flags);
>
> +	netc_timer_disable_pps_fiper(priv);
> +
>  	/* Adjusting TMROFF instead of TMR_CNT is that the timer
>  	 * counter keeps increasing during reading and writing
>  	 * TMR_CNT, which will cause latency.
> @@ -171,6 +349,8 @@ static int netc_timer_adjtime(struct ptp_clock_info *ptp, s64 delta)
>  	tmr_off += delta;
>  	netc_timer_offset_write(priv, tmr_off);
>
> +	netc_timer_enable_pps_fiper(priv);
> +
>  	spin_unlock_irqrestore(&priv->lock, flags);
>
>  	return 0;
> @@ -205,8 +385,12 @@ static int netc_timer_settime64(struct ptp_clock_info *ptp,
>  	unsigned long flags;
>
>  	spin_lock_irqsave(&priv->lock, flags);
> +
> +	netc_timer_disable_pps_fiper(priv);
>  	netc_timer_offset_write(priv, 0);
>  	netc_timer_cnt_write(priv, ns);
> +	netc_timer_enable_pps_fiper(priv);
> +
>  	spin_unlock_irqrestore(&priv->lock, flags);
>
>  	return 0;
> @@ -232,10 +416,13 @@ static const struct ptp_clock_info netc_timer_ptp_caps = {
>  	.name		= "NETC Timer PTP clock",
>  	.max_adj	= 500000000,
>  	.n_pins		= 0,
> +	.n_alarm	= 2,
> +	.pps		= 1,
>  	.adjfine	= netc_timer_adjfine,
>  	.adjtime	= netc_timer_adjtime,
>  	.gettimex64	= netc_timer_gettimex64,
>  	.settime64	= netc_timer_settime64,
> +	.enable		= netc_timer_enable,
>  };
>
>  static void netc_timer_init(struct netc_timer *priv)
> @@ -252,7 +439,7 @@ static void netc_timer_init(struct netc_timer *priv)
>  	 * domain are not accessible.
>  	 */
>  	tmr_ctrl = FIELD_PREP(TMR_CTRL_CK_SEL, priv->clk_select) |
> -		   TMR_CTRL_TE;
> +		   TMR_CTRL_TE | TMR_CTRL_FS;
>  	netc_timer_wr(priv, NETC_TMR_CTRL, tmr_ctrl);
>  	netc_timer_wr(priv, NETC_TMR_PRSC, priv->oclk_prsc);
>
> @@ -372,6 +559,66 @@ static int netc_timer_parse_dt(struct netc_timer *priv)
>  	return netc_timer_get_reference_clk_source(priv);
>  }
>
> +static irqreturn_t netc_timer_isr(int irq, void *data)
> +{
> +	struct netc_timer *priv = data;
> +	struct ptp_clock_event event;
> +	u32 tmr_event;
> +
> +	spin_lock(&priv->lock);
> +
> +	tmr_event = netc_timer_rd(priv, NETC_TMR_TEVENT);
> +	tmr_event &= priv->tmr_emask;
> +	/* Clear interrupts status */
> +	netc_timer_wr(priv, NETC_TMR_TEVENT, tmr_event);
> +
> +	if (tmr_event & TMR_TEVENT_ALMEN(0))
> +		netc_timer_alarm_write(priv, NETC_TMR_DEFAULT_ALARM, 0);
> +
> +	if (tmr_event & TMR_TEVENT_PPEN_ALL) {
> +		event.type = PTP_CLOCK_PPS;
> +		ptp_clock_event(priv->clock, &event);
> +	}
> +
> +	spin_unlock(&priv->lock);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int netc_timer_init_msix_irq(struct netc_timer *priv)
> +{
> +	struct pci_dev *pdev = priv->pdev;
> +	char irq_name[64];
> +	int err, n;
> +
> +	n = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSIX);
> +	if (n != 1) {
> +		err = (n < 0) ? n : -EPERM;
> +		dev_err(&pdev->dev, "pci_alloc_irq_vectors() failed\n");
> +		return err;
> +	}
> +
> +	priv->irq = pci_irq_vector(pdev, 0);
> +	snprintf(irq_name, sizeof(irq_name), "ptp-netc %s", pci_name(pdev));
> +	err = request_irq(priv->irq, netc_timer_isr, 0, irq_name, priv);
> +	if (err) {
> +		dev_err(&pdev->dev, "request_irq() failed\n");
> +		pci_free_irq_vectors(pdev);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static void netc_timer_free_msix_irq(struct netc_timer *priv)
> +{
> +	struct pci_dev *pdev = priv->pdev;
> +
> +	disable_irq(priv->irq);
> +	free_irq(priv->irq, priv);
> +	pci_free_irq_vectors(pdev);
> +}
> +
>  static int netc_timer_probe(struct pci_dev *pdev,
>  			    const struct pci_device_id *id)
>  {
> @@ -395,17 +642,23 @@ static int netc_timer_probe(struct pci_dev *pdev,
>  	priv->oclk_prsc = NETC_TMR_DEFAULT_PRSC;
>  	spin_lock_init(&priv->lock);
>
> +	err = netc_timer_init_msix_irq(priv);
> +	if (err)
> +		goto timer_pci_remove;
> +
>  	netc_timer_init(priv);
>  	priv->clock = ptp_clock_register(&priv->caps, dev);
>  	if (IS_ERR(priv->clock)) {
>  		err = PTR_ERR(priv->clock);
> -		goto timer_pci_remove;
> +		goto free_msix_irq;
>  	}
>
>  	priv->phc_index = ptp_clock_index(priv->clock);
>
>  	return 0;
>
> +free_msix_irq:
> +	netc_timer_free_msix_irq(priv);
>  timer_pci_remove:
>  	netc_timer_pci_remove(pdev);
>
> @@ -417,6 +670,7 @@ static void netc_timer_remove(struct pci_dev *pdev)
>  	struct netc_timer *priv = pci_get_drvdata(pdev);
>
>  	ptp_clock_unregister(priv->clock);
> +	netc_timer_free_msix_irq(priv);
>  	netc_timer_pci_remove(pdev);
>  }
>
> --
> 2.34.1
>

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