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Message-ID: <aK8gODZD15OP//V7@lizhi-Precision-Tower-5810>
Date: Wed, 27 Aug 2025 11:11:52 -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, fushi.peng@....com, devicetree@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
imx@...ts.linux.dev
Subject: Re: [PATCH v6 net-next 04/17] ptp: add debugfs interfaces to loop
back the periodic output signal
On Wed, Aug 27, 2025 at 02:33:19PM +0800, Wei Fang wrote:
> For some PTP devices, they have the capability to loop back the periodic
> output signal for debugging, such as the ptp_qoriq device. So add the
> generic interfaces to set the periodic output signal loopback, rather
> than each vendor having a different implementation.
>
> Show how many channels support the periodic output signal loopback:
> $ cat /sys/kernel/debug/ptp<N>/n_perout_loopback
>
> Enable the loopback of the periodic output signal of channel X:
> $ echo <X> 1 > /sys/kernel/debug/ptp<N>/perout_loopback
Genernally sys interface only 1 input for each entry.
I suggest create one file for each channel.
/sys/kernel/debug/ptp<N>/perout<m>_loopback_enable
echo 1 > /sys/kernel/debug/ptp<N>/perout<m>_loopback_enable
Frank
>
> Disable the loopback of the periodic output signal of channel X:
> $ echo <X> 0 > /sys/kernel/debug/ptp<N>/perout_loopback
>
> Suggested-by: Andrew Lunn <andrew@...n.ch>
> Signed-off-by: Wei Fang <wei.fang@....com>
>
> ---
> v6 changes:
> 1. New patch
> ---
> drivers/ptp/ptp_clock.c | 66 ++++++++++++++++++++++++++++++++
> include/linux/ptp_clock_kernel.h | 10 +++++
> 2 files changed, 76 insertions(+)
>
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index 2b0fd62a17ef..0a45c5ebd904 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -237,6 +237,66 @@ static void ptp_aux_kworker(struct kthread_work *work)
> kthread_queue_delayed_work(ptp->kworker, &ptp->aux_work, delay);
> }
>
> +static ssize_t ptp_n_perout_loopback_read(struct file *filep,
> + char __user *buffer,
> + size_t count, loff_t *pos)
> +{
> + struct ptp_clock *ptp = filep->private_data;
> + char buf[12] = {};
> +
> + snprintf(buf, sizeof(buf), "%d\n", ptp->info->n_per_lp);
> +
> + return simple_read_from_buffer(buffer, count, pos, buf, strlen(buf));
> +}
> +
> +static const struct file_operations ptp_n_perout_loopback_fops = {
> + .owner = THIS_MODULE,
> + .open = simple_open,
> + .read = ptp_n_perout_loopback_read,
> +};
> +
> +static ssize_t ptp_perout_loopback_write(struct file *filep,
> + const char __user *buffer,
> + size_t count, loff_t *ppos)
> +{
> + struct ptp_clock *ptp = filep->private_data;
> + struct ptp_clock_info *ops = ptp->info;
> + int len, cnt, enable, err;
> + unsigned int index;
> + char buf[32] = {};
> +
> + if (*ppos || !count)
> + return -EINVAL;
> +
> + if (count >= sizeof(buf))
> + return -ENOSPC;
> +
> + len = simple_write_to_buffer(buf, sizeof(buf) - 1,
> + ppos, buffer, count);
> + if (len < 0)
> + return len;
> +
> + buf[len] = '\0';
> + cnt = sscanf(buf, "%u %d", &index, &enable);
> + if (cnt != 2)
> + return -EINVAL;
> +
> + if (index >= ops->n_per_lp)
> + return -EINVAL;
> +
> + err = ops->perout_loopback(ops, index, enable ? 1 : 0);
> + if (err)
> + return err;
> +
> + return count;
> +}
> +
> +static const struct file_operations ptp_perout_loopback_ops = {
> + .owner = THIS_MODULE,
> + .open = simple_open,
> + .write = ptp_perout_loopback_write,
> +};
> +
> /* public interface */
>
> struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
> @@ -378,6 +438,12 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
> /* Debugfs initialization */
> snprintf(debugfsname, sizeof(debugfsname), "ptp%d", ptp->index);
> ptp->debugfs_root = debugfs_create_dir(debugfsname, NULL);
> + if (info->n_per_lp > 0 && info->perout_loopback) {
> + debugfs_create_file("n_perout_loopback", 0400, ptp->debugfs_root,
> + ptp, &ptp_n_perout_loopback_fops);
> + debugfs_create_file("perout_loopback", 0200, ptp->debugfs_root,
> + ptp, &ptp_perout_loopback_ops);
> + }
>
> return ptp;
>
> diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
> index 7dd7951b23d5..884364596dd3 100644
> --- a/include/linux/ptp_clock_kernel.h
> +++ b/include/linux/ptp_clock_kernel.h
> @@ -67,6 +67,8 @@ struct ptp_system_timestamp {
> * @n_ext_ts: The number of external time stamp channels.
> * @n_per_out: The number of programmable periodic signals.
> * @n_pins: The number of programmable pins.
> + * @n_per_lp: The number of channels that support loopback the periodic
> + * output signal.
> * @pps: Indicates whether the clock supports a PPS callback.
> *
> * @supported_perout_flags: The set of flags the driver supports for the
> @@ -175,6 +177,11 @@ struct ptp_system_timestamp {
> * scheduling time (>=0) or negative value in case further
> * scheduling is not required.
> *
> + * @perout_loopback: Request driver to enable or disable the periodic output
> + * signal loopback.
> + * parameter index: index of the periodic output signal channel.
> + * parameter on: caller passes one to enable or zero to disable.
> + *
> * Drivers should embed their ptp_clock_info within a private
> * structure, obtaining a reference to it using container_of().
> *
> @@ -189,6 +196,7 @@ struct ptp_clock_info {
> int n_ext_ts;
> int n_per_out;
> int n_pins;
> + int n_per_lp;
> int pps;
> unsigned int supported_perout_flags;
> unsigned int supported_extts_flags;
> @@ -213,6 +221,8 @@ struct ptp_clock_info {
> int (*verify)(struct ptp_clock_info *ptp, unsigned int pin,
> enum ptp_pin_function func, unsigned int chan);
> long (*do_aux_work)(struct ptp_clock_info *ptp);
> + int (*perout_loopback)(struct ptp_clock_info *ptp, unsigned int index,
> + int on);
> };
>
> struct ptp_clock;
> --
> 2.34.1
>
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