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.loktio...@intel.com>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalew...@intel.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.kubalew...@intel.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
