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Message-Id: <20241106010756.1588973-2-arkadiusz.kubalewski@intel.com>
Date: Wed, 6 Nov 2024 02:07:55 +0100
From: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
To: netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
intel-wired-lan@...ts.osuosl.org
Cc: anthony.l.nguyen@...el.com,
przemyslaw.kitszel@...el.com,
davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
richardcochran@...il.com,
Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Subject: [PATCH net-next v3 1/2] ptp: add control over HW timestamp latch point
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. Provide a new file under sysfs
ptp device (/sys/class/ptp/ptp<N>/ts_point). The file is available for the
user, if the device driver implements at least one of newly provided
callbacks. If the file is not provided the user shall find a PHY timestamp
latch point within the HW vendor specification.
The file is designed for root user/group access only, as the read for
regular user could impact performance of the ptp device.
Usage, examples:
** Obtain current state:
$ cat /sys/class/ptp/ptp<N>/ts_point
Command returns enum/integer:
* 1 - timestamp latched by PHY at the beginning of SFD,
* 2 - timestamp latched by PHY after the SFD,
* None - callback returns error to the user.
** Configure timestamp latch point at the beginning of SFD:
$ echo 1 > /sys/class/ptp/ptp<N>/ts_point
** Configure timestamp latch point after the SFD:
$ echo 2 > /sys/class/ptp/ptp<N>/ts_point
[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>
---
v3:
- max value of enum ptp_ts_point is also enumerated,
- move enum ptp_ts_point to uapi,
- add NONE value to enum ptp_ts_point, to make clear that value was
not provided, thus allow further extension of ethtool netlink.
---
Documentation/ABI/testing/sysfs-ptp | 12 ++++++++
drivers/ptp/ptp_sysfs.c | 44 +++++++++++++++++++++++++++++
include/linux/ptp_clock_kernel.h | 12 ++++++++
include/uapi/linux/ptp_clock.h | 18 ++++++++++++
4 files changed, 86 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-ptp b/Documentation/ABI/testing/sysfs-ptp
index 9c317ac7c47a..063b3e20386e 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 "1" means the timestamp is latched at the
+ beginning of the SFD. Value "2" means that timestamp is
+ latched after the end of SFD.
diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c
index 6b1b8f57cd95..2f3f28edbbfd 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_NONE || 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(ts_point, 0660, ts_point_show, ts_point_store);
+
#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..d48619c7c60a 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -159,6 +159,14 @@ 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 +203,10 @@ 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;
diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
index 18eefa6d93d6..11a9dad9db00 100644
--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h
@@ -253,4 +253,22 @@ struct ptp_extts_event {
unsigned int rsv[2]; /* Reserved for future use. */
};
+/**
+ * enum ptp_ts_point - possible timestamp latch points (IEEE 802.3cx)
+ *
+ * @PTP_TS_POINT_NONE: no timestamp latch point was provided
+ * @PTP_TS_POINT_SFD: timestamp latched at the beginning of sending Start
+ * 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_NONE = 0,
+ PTP_TS_POINT_SFD,
+ PTP_TS_POINT_POST_SFD,
+
+ /* private: */
+ PTP_TS_POINT_MAX
+};
+
#endif
--
2.38.1
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