netdev - [RFC 1/3] ptp: Implement timex esterror support

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Message-Id: <20240813125602.155827-2-maciek@machnikowski.net>
Date: Tue, 13 Aug 2024 12:56:00 +0000
From: Maciek Machnikowski <maciek@...hnikowski.net>
To: maciek@...hnikowski.net
Cc: netdev@...r.kernel.org,
	richardcochran@...il.com,
	jacob.e.keller@...el.com,
	vadfed@...a.com,
	darinzon@...zon.com,
	kuba@...nel.org
Subject: [RFC 1/3] ptp: Implement timex esterror support

The Timex structure returned by the clock_adjtime() POSIX API allows
the clock to return the estimated error. Implement getesterror
and setesterror functions in the ptp_clock_info to enable drivers
to interact with the hardware to get the error information.

getesterror additionally implements returning hw_ts and sys_ts
to enable upper layers to estimate the maximum error of the clock
based on the last time of correction. This functionality is not
directly implemented in the clock_adjtime and will require
a separate interface in the future.

Signed-off-by: Maciek Machnikowski <maciek@...hnikowski.net>
---
 drivers/ptp/ptp_clock.c          | 18 +++++++++++++++++-
 include/linux/ptp_clock_kernel.h | 11 +++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index c56cd0f63909..2cb1f6af60ea 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -164,9 +164,25 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
 
 			err = ops->adjphase(ops, offset);
 		}
+	} else if (tx->modes & ADJ_ESTERROR) {
+		if (ops->setesterror)
+			if (tx->modes & ADJ_NANO)
+				err = ops->setesterror(ops, tx->esterror * 1000);
+			else
+				err = ops->setesterror(ops, tx->esterror);
 	} else if (tx->modes == 0) {
+		long esterror;
+
 		tx->freq = ptp->dialed_frequency;
-		err = 0;
+		if (ops->getesterror) {
+			err = ops->getesterror(ops, &esterror, NULL, NULL);
+			if (err)
+				return err;
+			tx->modes &= ADJ_NANO;
+			tx->esterror = esterror;
+		} else {
+			err = 0;
+		}
 	}
 
 	return err;
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 6e4b8206c7d0..e78ea81fc4cf 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -136,6 +136,14 @@ struct ptp_system_timestamp {
  *                   parameter cts: Contains timestamp (device,system) pair,
  *                   where system time is realtime and monotonic.
  *
+ * @getesterror: Reads the current error estimate of the hardware clock.
+ *               parameter phase: Holds the error estimate in nanoseconds.
+ *               parameter hw_ts: If not NULL, holds the timestamp of the hardware clock.
+ *               parameter sw_ts: If not NULL, holds the timestamp of the CPU clock.
+ *
+ * @setesterror:  Set the error estimate of the hardware clock.
+ *                parameter phase: Desired error estimate in nanoseconds.
+ *
  * @enable:   Request driver to enable or disable an ancillary feature.
  *            parameter request: Desired resource to enable or disable.
  *            parameter on: Caller passes one to enable or zero to disable.
@@ -188,6 +196,9 @@ struct ptp_clock_info {
 			    struct ptp_system_timestamp *sts);
 	int (*getcrosscycles)(struct ptp_clock_info *ptp,
 			      struct system_device_crosststamp *cts);
+	int (*getesterror)(struct ptp_clock_info *ptp, long *phase,
+			   struct timespec64 *hw_ts, struct timespec64 *sys_ts);
+	int (*setesterror)(struct ptp_clock_info *ptp, long phase);
 	int (*enable)(struct ptp_clock_info *ptp,
 		      struct ptp_clock_request *request, int on);
 	int (*verify)(struct ptp_clock_info *ptp, unsigned int pin,
-- 
2.34.1