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Message-ID: <15688d2d-b3a0-4730-9cee-15bb6c7f78fb@molgen.mpg.de>
Date: Mon, 21 Oct 2024 17:20:59 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
intel-wired-lan@...ts.osuosl.org, anthony.l.nguyen@...el.com,
przemyslaw.kitszel@...el.com, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, richardcochran@...il.com,
Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH net-next 1/2] ptp: add control over HW
timestamp latch point
Dear Arkadiusz,
Thank you for your patch.
Am 21.10.24 um 16:19 schrieb Arkadiusz Kubalewski:
> Currently HW support of PTP/timesync solutions in network PHY chips can be
> implemented with two different approaches, the timestamp maybe latched
> either at the beginning or after the Start of Frame Delimiter (SFD) [1].
>
> Allow ptp device drivers to provide user with control over the HW
> timestamp latch point with ptp sysfs ABI.
Please describe, that it’s done using `/sys` filesystem.
How can this be tested?
> [1] https://www.ieee802.org/3/cx/public/april20/tse_3cx_01_0420.pdf
>
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>
> Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
> ---
> Documentation/ABI/testing/sysfs-ptp | 12 ++++++++
> drivers/ptp/ptp_sysfs.c | 44 +++++++++++++++++++++++++++++
> include/linux/ptp_clock_kernel.h | 29 +++++++++++++++++++
> 3 files changed, 85 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-ptp b/Documentation/ABI/testing/sysfs-ptp
> index 9c317ac7c47a..a0d89e0fd72e 100644
> --- a/Documentation/ABI/testing/sysfs-ptp
> +++ b/Documentation/ABI/testing/sysfs-ptp
> @@ -140,3 +140,15 @@ Description:
> PPS events to the Linux PPS subsystem. To enable PPS
> events, write a "1" into the file. To disable events,
> write a "0" into the file.
> +
> +What: /sys/class/ptp/ptp<N>/ts_point
> +Date: October 2024
> +Contact: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
> +Description:
> + This file provides control over the point in time in
> + which the HW timestamp is latched. As specified in IEEE
> + 802.3cx, the latch point can be either at the beginning
> + or after the end of Start of Frame Delimiter (SFD).
> + Value "0" means the timestamp is latched at the
> + beginning of the SFD. Value "1" means that timestamp is
> + latched after the end of SFD.
Would it make sense to let it be configured by strings, so it’s clear,
what the values mean?
1. beginning_of_sfd
2. end_of_sfd
> diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c
> index 6b1b8f57cd95..7e9f6ef368b6 100644
> --- a/drivers/ptp/ptp_sysfs.c
> +++ b/drivers/ptp/ptp_sysfs.c
> @@ -28,6 +28,46 @@ static ssize_t max_phase_adjustment_show(struct device *dev,
> }
> static DEVICE_ATTR_RO(max_phase_adjustment);
>
> +static ssize_t ts_point_show(struct device *dev, struct device_attribute *attr,
> + char *page)
> +{
> + struct ptp_clock *ptp = dev_get_drvdata(dev);
> + enum ptp_ts_point point;
> + int err;
> +
> + if (!ptp->info->get_ts_point)
> + return -EOPNOTSUPP;
> + err = ptp->info->get_ts_point(ptp->info, &point);
> + if (err)
> + return err;
> +
> + return sysfs_emit(page, "%d\n", point);
> +}
> +
> +static ssize_t ts_point_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct ptp_clock *ptp = dev_get_drvdata(dev);
> + enum ptp_ts_point point;
> + int err;
> + u8 val;
> +
> + if (!ptp->info->set_ts_point)
> + return -EOPNOTSUPP;
> + if (kstrtou8(buf, 0, &val))
> + return -EINVAL;
> + if (val > PTP_TS_POINT_MAX)
> + return -EINVAL;
> + point = val;
> +
> + err = ptp->info->set_ts_point(ptp->info, point);
> + if (err)
> + return err;
> +
> + return count;
> +}
> +static DEVICE_ATTR_RW(ts_point);
> +
> #define PTP_SHOW_INT(name, var) \
> static ssize_t var##_show(struct device *dev, \
> struct device_attribute *attr, char *page) \
> @@ -335,6 +375,7 @@ static struct attribute *ptp_attrs[] = {
> &dev_attr_pps_enable.attr,
> &dev_attr_n_vclocks.attr,
> &dev_attr_max_vclocks.attr,
> + &dev_attr_ts_point.attr,
> NULL
> };
>
> @@ -363,6 +404,9 @@ static umode_t ptp_is_attribute_visible(struct kobject *kobj,
> } else if (attr == &dev_attr_max_phase_adjustment.attr) {
> if (!info->adjphase || !info->getmaxphase)
> mode = 0;
> + } else if (attr == &dev_attr_ts_point.attr) {
> + if (!info->get_ts_point && !info->set_ts_point)
> + mode = 0;
> }
>
> return mode;
> diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
> index c892d22ce0a7..921d6615bd39 100644
> --- a/include/linux/ptp_clock_kernel.h
> +++ b/include/linux/ptp_clock_kernel.h
> @@ -55,6 +55,23 @@ struct ptp_system_timestamp {
> clockid_t clockid;
> };
>
> +/**
> + * enum ptp_ts_point - possible timestamp latch points (IEEE 802.3cx)
> + * @PTP_TS_POINT_SFD: timestamp latched at the beginning of sending Start
The alignment of the start of the description looks strange with the
second line being further right.
> + * of Frame Delimiter (SFD)
> + * @PTP_TS_POINT_POST_SFD: timestamp latched after the end of sending Start
> + * of Frame Delimiter (SFD)
> + */
> +enum ptp_ts_point {
> + PTP_TS_POINT_SFD,
> + PTP_TS_POINT_POST_SFD,
> +
> + /* private: */
> + __PTP_TS_POINT_MAX
> +};
> +
> +#define PTP_TS_POINT_MAX (__PTP_TS_POINT_MAX - 1)
> +
> /**
> * struct ptp_clock_info - describes a PTP hardware clock
> *
> @@ -159,6 +176,14 @@ struct ptp_system_timestamp {
> * scheduling time (>=0) or negative value in case further
> * scheduling is not required.
> *
> + * @set_ts_point: Request change of timestamp latch point, as the timestamp
> + * could be latched at the beginning or after the end of start
> + * frame delimiter (SFD), as described in IEEE 802.3cx
> + * specification.
> + *
> + * @get_ts_point: Obtain the timestamp measurement latch point, counterpart of
> + * .set_ts_point() for getting currently configured value.
> + *
> * Drivers should embed their ptp_clock_info within a private
> * structure, obtaining a reference to it using container_of().
> *
> @@ -195,6 +220,10 @@ 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 (*set_ts_point)(struct ptp_clock_info *ptp,
> + enum ptp_ts_point point);
> + int (*get_ts_point)(struct ptp_clock_info *ptp,
> + enum ptp_ts_point *point);
> };
>
> struct ptp_clock;
Kind regards,
Paul
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