ptpcheck: phc: add clock setting function (#402)

Summary:
Pull Request resolved: #402

Enable the `ptpcheck phc` command to set the PTP clock to a given value.

The new flag, `-s`, takes a Unix timestamp as an argument, and writes it to the PTP device. The resolution is thus limited to whole seconds, so the clock then requires a more precise tuning – achievable, for example, with the sptp program.

Reviewed By: abulimov

Differential Revision: D64134612

fbshipit-source-id: 5f89bb96a5539760476a72d11cc24191b6184ab7

clock/clock.go

@@ -58,6 +58,7 @@ const (
 
 // Adjtime issues CLOCK_ADJTIME syscall to either adjust the parameters of given clock,
 // or read them if buf is empty.  man(2) clock_adjtime
+// TODO: replace this with a call to https://pkg.go.dev/golang.org/x/sys/unix#ClockAdjtime
 func Adjtime(clockid int32, buf *unix.Timex) (state int, err error) {
 	r0, _, errno := unix.Syscall(unix.SYS_CLOCK_ADJTIME, uintptr(clockid), uintptr(unsafe.Pointer(buf)), 0)
 	state = int(r0)
@@ -67,6 +68,16 @@ func Adjtime(clockid int32, buf *unix.Timex) (state int, err error) {
 	return state, err
 }
 
+// Settime issues clock_settime(3) syscall to set the time of the specified clock.
+// TODO: issue a PR for golang.org/x/sys/unix to add this function there
+func Settime(clockid int32, time *unix.Timespec) (err error) {
+	_, _, errno := unix.Syscall(unix.SYS_CLOCK_SETTIME, uintptr(clockid), uintptr(unsafe.Pointer(time)), 0)
+	if errno != 0 {
+		err = errno
+	}
+	return err
+}
+
 // FrequencyPPB reads device frequency in PPB
 func FrequencyPPB(clockid int32) (freqPPB float64, state int, err error) {
 	tx := &unix.Timex{}

cmd/ptpcheck/cmd/phc.go

@@ -34,6 +34,7 @@ var (
 	method      string
 	freq        float64
 	step        time.Duration
+	unixSec     int64
 	setAndPrint bool
 )
 
@@ -52,13 +53,20 @@ func init() {
 	)
 	flags.Float64VarP(&freq, "freq", "f", math.NaN(), "set the frequency (PPB)")
 	flags.DurationVarP(&step, "step", "t", 0, "step the clock")
+	flags.Int64VarP(&unixSec, "set", "s", -1, "set the clock to Unix seconds, like $(date +%s)")
 	flags.BoolVarP(&setAndPrint, "print", "p", false, "print clock status after changes")
 }
 
 func runPhcCmd(_ *cobra.Command, _ []string) {
 	var doPrint = true
 
 	ConfigureVerbosity()
+	if unixSec != -1 {
+		if err := setPHC(device, unixSec); err != nil {
+			log.Fatal(err)
+		}
+		doPrint = setAndPrint
+	}
 	if step != 0 {
 		if err := stepPHC(device, step); err != nil {
 			log.Fatal(err)
@@ -78,6 +86,20 @@ func runPhcCmd(_ *cobra.Command, _ []string) {
 	}
 }
 
+func setPHC(device string, unixSec int64) error {
+	f, err := os.OpenFile(device, os.O_RDWR, 0)
+	if err != nil {
+		return fmt.Errorf("opening device %q: %w", device, err)
+	}
+	defer f.Close()
+	dev := phc.FromFile(f)
+
+	t := time.Unix(unixSec, 0)
+
+	fmt.Printf("Setting the clock to %v (%v in Unix seconds)\n", t, unixSec)
+	return dev.SetTime(t)
+}
+
 func stepPHC(device string, step time.Duration) error {
 	f, err := os.OpenFile(device, os.O_RDWR, 0)
 	if err != nil {
@@ -121,8 +143,12 @@ func printPHC(device string, method phc.TimeMethod) error {
 			return err
 		}
 	}
-	fmt.Printf("PHC clock: %s\n", timeAndOffset.PHCTime)
-	fmt.Printf("SYS clock: %s\n", timeAndOffset.SysTime)
+
+	timePHC := timeAndOffset.PHCTime
+	timeSys := timeAndOffset.SysTime
+
+	fmt.Printf("PHC clock: %s (%v in Unix seconds)\n", timePHC, timePHC.Unix())
+	fmt.Printf("SYS clock: %s (%v in Unix seconds)\n", timeSys, timeSys.Unix())
 	fmt.Printf("Offset: %s\n", timeAndOffset.Offset)
 	fmt.Printf("Delay: %s\n", timeAndOffset.Delay)
 

phc/adjtime.go

@@ -61,3 +61,11 @@ func clockStep(dev *Device, step time.Duration) error {
 	}
 	return err
 }
+
+func clockSetTime(dev *Device, t time.Time) error {
+	ts, err := unix.TimeToTimespec(t)
+	if err != nil {
+		return err
+	}
+	return clock.Settime(dev.ClockID(), &ts)
+}

phc/phc.go

@@ -288,6 +288,9 @@ func (dev *Device) AdjFreq(freqPPB float64) error { return clockAdjFreq(dev, fre
 // Step steps the PHC clock by given duration
 func (dev *Device) Step(step time.Duration) error { return clockStep(dev, step) }
 
+// SetTime sets the time of the PHC clock
+func (dev *Device) SetTime(t time.Time) error { return clockSetTime(dev, t) }
+
 func (dev *Device) Read(buffer []byte) (int, error) {
 	return syscall.Read(int(dev.Fd()), buffer)
 }