Re: [PATCH v3 net-next 08/15] ptp: netc: add debugfs support to loop back pulse signal

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

On Tue, Aug 12, 2025 at 05:46:27PM +0800, Wei Fang wrote:
> The NETC Timer supports to loop back the output pulse signal of Fiper-n
> into Trigger-n input, so that we can leverage this feature to validate
> some other features without external hardware support. For example, we
> can use it to test external trigger stamp (EXTTS). And we can combine
> EXTTS with loopback mode to check whether the generation time of PPS is
> aligned with an integral second of PHC, or the periodic output signal
> (PTP_CLK_REQ_PEROUT) whether is generated at the specified time. So add
> the debugfs interfaces to enable the loopback mode of Fiper1 and Fiper2.

The NETC Timer supports to loop back the output pulse signal of Fiper-n
into Trigger-n input. Add debugfs interfaces to enable loopback for PTP
feature validation without external hardware support.

See below typical user case:

>
> An example to test the generation time of PPS event.

Test the generation time of PPS event:

>
> $ echo 1 > /sys/kernel/debug/netc_timer0/fiper1-loopback
> $ echo 1 > /sys/class/ptp/ptp0/pps_enable
> $ testptp -d /dev/ptp0 -e 3
> external time stamp request okay
> event index 0 at 108.000000018
> event index 0 at 109.000000018
> event index 0 at 110.000000018
>
> An example to test the generation time of the periodic output signal.

Test generation time of the periodic output signal.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
>
> $ echo 1 > /sys/kernel/debug/netc_timer0/fiper1-loopback
> $ echo 0 260 0 1 500000000 > /sys/class/ptp/ptp0/period
> $ testptp -d /dev/ptp0 -e 3
> external time stamp request okay
> event index 0 at 260.000000016
> event index 0 at 261.500000015
> event index 0 at 263.000000016
>
> Signed-off-by: Wei Fang <wei.fang@nxp.com>
> ---
> v2 changes:
> 1. Remove the check of the return value of debugfs_create_dir()
> v3 changes:
> 1. Rename TMR_CTRL_PP1L and TMR_CTRL_PP2L to TMR_CTRL_PPL(i)
> 2. Remove switch statement from netc_timer_get_fiper_loopback() and
>    netc_timer_set_fiper_loopback()
> ---
>  drivers/ptp/ptp_netc.c | 94 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 94 insertions(+)
>
> diff --git a/drivers/ptp/ptp_netc.c b/drivers/ptp/ptp_netc.c
> index 45d60ad46b68..d483fad51c66 100644
> --- a/drivers/ptp/ptp_netc.c
> +++ b/drivers/ptp/ptp_netc.c
> @@ -6,6 +6,7 @@
>
>  #include <linux/bitfield.h>
>  #include <linux/clk.h>
> +#include <linux/debugfs.h>
>  #include <linux/fsl/netc_global.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> @@ -21,6 +22,7 @@
>  #define  TMR_ETEP(i)			BIT(8 + (i))
>  #define  TMR_COMP_MODE			BIT(15)
>  #define  TMR_CTRL_TCLK_PERIOD		GENMASK(25, 16)
> +#define  TMR_CTRL_PPL(i)		BIT(27 - (i))
>  #define  TMR_CTRL_FS			BIT(28)
>
>  #define NETC_TMR_TEVENT			0x0084
> @@ -122,6 +124,7 @@ struct netc_timer {
>  	u8 fs_alarm_num;
>  	u8 fs_alarm_bitmap;
>  	struct netc_pp pp[NETC_TMR_FIPER_NUM]; /* periodic pulse */
> +	struct dentry *debugfs_root;
>  };
>
>  #define netc_timer_rd(p, o)		netc_read((p)->base + (o))
> @@ -953,6 +956,95 @@ static int netc_timer_get_global_ip_rev(struct netc_timer *priv)
>  	return val & IPBRR0_IP_REV;
>  }
>
> +static int netc_timer_get_fiper_loopback(struct netc_timer *priv,
> +					 int fiper, u64 *val)
> +{
> +	unsigned long flags;
> +	u32 tmr_ctrl;
> +
> +	spin_lock_irqsave(&priv->lock, flags);
> +	tmr_ctrl = netc_timer_rd(priv, NETC_TMR_CTRL);
> +	spin_unlock_irqrestore(&priv->lock, flags);
> +
> +	*val = (tmr_ctrl & TMR_CTRL_PPL(fiper)) ? 1 : 0;
> +
> +	return 0;
> +}
> +
> +static int netc_timer_set_fiper_loopback(struct netc_timer *priv,
> +					 int fiper, bool en)
> +{
> +	unsigned long flags;
> +	u32 tmr_ctrl;
> +
> +	spin_lock_irqsave(&priv->lock, flags);
> +
> +	tmr_ctrl = netc_timer_rd(priv, NETC_TMR_CTRL);
> +	if (en)
> +		tmr_ctrl |= TMR_CTRL_PPL(fiper);
> +	else
> +		tmr_ctrl &= ~TMR_CTRL_PPL(fiper);
> +
> +	netc_timer_wr(priv, NETC_TMR_CTRL, tmr_ctrl);
> +
> +	spin_unlock_irqrestore(&priv->lock, flags);
> +
> +	return 0;
> +}
> +
> +static int netc_timer_get_fiper1_loopback(void *data, u64 *val)
> +{
> +	struct netc_timer *priv = data;
> +
> +	return netc_timer_get_fiper_loopback(priv, 0, val);
> +}
> +
> +static int netc_timer_set_fiper1_loopback(void *data, u64 val)
> +{
> +	struct netc_timer *priv = data;
> +
> +	return netc_timer_set_fiper_loopback(priv, 0, !!val);
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(netc_timer_fiper1_fops, netc_timer_get_fiper1_loopback,
> +			 netc_timer_set_fiper1_loopback, "%llu\n");
> +
> +static int netc_timer_get_fiper2_loopback(void *data, u64 *val)
> +{
> +	struct netc_timer *priv = data;
> +
> +	return netc_timer_get_fiper_loopback(priv, 1, val);
> +}
> +
> +static int netc_timer_set_fiper2_loopback(void *data, u64 val)
> +{
> +	struct netc_timer *priv = data;
> +
> +	return netc_timer_set_fiper_loopback(priv, 1, !!val);
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(netc_timer_fiper2_fops, netc_timer_get_fiper2_loopback,
> +			 netc_timer_set_fiper2_loopback, "%llu\n");
> +
> +static void netc_timer_create_debugfs(struct netc_timer *priv)
> +{
> +	char debugfs_name[24];
> +
> +	snprintf(debugfs_name, sizeof(debugfs_name), "netc_timer%d",
> +		 priv->phc_index);
> +	priv->debugfs_root = debugfs_create_dir(debugfs_name, NULL);
> +	debugfs_create_file("fiper1-loopback", 0600, priv->debugfs_root,
> +			    priv, &netc_timer_fiper1_fops);
> +	debugfs_create_file("fiper2-loopback", 0600, priv->debugfs_root,
> +			    priv, &netc_timer_fiper2_fops);
> +}
> +
> +static void netc_timer_remove_debugfs(struct netc_timer *priv)
> +{
> +	debugfs_remove(priv->debugfs_root);
> +	priv->debugfs_root = NULL;
> +}
> +
>  static int netc_timer_probe(struct pci_dev *pdev,
>  			    const struct pci_device_id *id)
>  {
> @@ -995,6 +1087,7 @@ static int netc_timer_probe(struct pci_dev *pdev,
>  	}
>
>  	priv->phc_index = ptp_clock_index(priv->clock);
> +	netc_timer_create_debugfs(priv);
>
>  	return 0;
>
> @@ -1010,6 +1103,7 @@ static void netc_timer_remove(struct pci_dev *pdev)
>  {
>  	struct netc_timer *priv = pci_get_drvdata(pdev);
>
> +	netc_timer_remove_debugfs(priv);
>  	ptp_clock_unregister(priv->clock);
>  	netc_timer_free_msix_irq(priv);
>  	netc_timer_pci_remove(pdev);
> --
> 2.34.1
>