Merge branch 'PHC-freq-fine-tuning'

Richard Cochran says:

====================
PHC frequency fine tuning

This series expands the PTP Hardware Clock subsystem by adding a
method that passes the frequency tuning word to the the drivers
without dropping the low order bits.  Keeping those bits is useful for
drivers whose frequency resolution is higher than 1 ppb.

The appended script (below) runs a simple demonstration of the
improvement.  This test needs two Intel i210 PCIe cards installed in
the same PC, with their SDP0 pins connected by copper wire.  Measuring
the estimated offset (from the ptp4l servo) and the true offset (from
the PPS) over one hour yields the following statistics.

|        |   Est. Before |    Est. After |   True Before |    True After |
|--------+---------------+---------------+---------------+---------------|
| min    | -5.200000e+01 | -1.600000e+01 | -3.100000e+01 | -1.000000e+00 |
| max    | +5.700000e+01 | +2.500000e+01 | +8.500000e+01 | +4.000000e+01 |
| pk-pk: | +1.090000e+02 | +4.100000e+01 | +1.160000e+02 | +4.100000e+01 |
| mean   | +6.472222e-02 | +1.277778e-02 | +2.422083e+01 | +1.826083e+01 |
| stddev | +1.158006e+01 | +4.581982e+00 | +1.207708e+01 | +4.981435e+00 |

Here the numbers in units of nanoseconds, and the ~20 nanosecond PPS
offset is due to input/output delays on the i210's external interface
logic.

With the series applied, both the peak to peak error and the standard
deviation improve by a factor of more than two.  These two graphs show
the improvement nicely.

  http://linuxptp.sourceforge.net/fine-tuning/fine-est.png

  http://linuxptp.sourceforge.net/fine-tuning/fine-tru.png
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 27 insertions, 16 deletions

diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
index a7895c4cbcc3e0..c30eea8399a7df 100644
--- a/drivers/net/ethernet/intel/igb/igb_ptp.c
+++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
@@ -226,7 +226,7 @@ static int igb_ptp_adjfreq_82576(struct ptp_clock_info *ptp, s32 ppb)
 	return 0;
 }
 
-static int igb_ptp_adjfreq_82580(struct ptp_clock_info *ptp, s32 ppb)
+static int igb_ptp_adjfine_82580(struct ptp_clock_info *ptp, long scaled_ppm)
 {
 	struct igb_adapter *igb = container_of(ptp, struct igb_adapter,
 					       ptp_caps);
@@ -235,13 +235,13 @@ static int igb_ptp_adjfreq_82580(struct ptp_clock_info *ptp, s32 ppb)
 	u64 rate;
 	u32 inca;
 
-	if (ppb < 0) {
+	if (scaled_ppm < 0) {
 		neg_adj = 1;
-		ppb = -ppb;
+		scaled_ppm = -scaled_ppm;
 	}
-	rate = ppb;
-	rate <<= 26;
-	rate = div_u64(rate, 1953125);
+	rate = scaled_ppm;
+	rate <<= 13;
+	rate = div_u64(rate, 15625);
 
 	inca = rate & INCVALUE_MASK;
 	if (neg_adj)
@@ -1103,7 +1103,7 @@ void igb_ptp_init(struct igb_adapter *adapter)
 		adapter->ptp_caps.max_adj = 62499999;
 		adapter->ptp_caps.n_ext_ts = 0;
 		adapter->ptp_caps.pps = 0;
-		adapter->ptp_caps.adjfreq = igb_ptp_adjfreq_82580;
+		adapter->ptp_caps.adjfine = igb_ptp_adjfine_82580;
 		adapter->ptp_caps.adjtime = igb_ptp_adjtime_82576;
 		adapter->ptp_caps.gettime64 = igb_ptp_gettime_82576;
 		adapter->ptp_caps.settime64 = igb_ptp_settime_82576;
@@ -1131,7 +1131,7 @@ void igb_ptp_init(struct igb_adapter *adapter)
 		adapter->ptp_caps.n_pins = IGB_N_SDP;
 		adapter->ptp_caps.pps = 1;
 		adapter->ptp_caps.pin_config = adapter->sdp_config;
-		adapter->ptp_caps.adjfreq = igb_ptp_adjfreq_82580;
+		adapter->ptp_caps.adjfine = igb_ptp_adjfine_82580;
 		adapter->ptp_caps.adjtime = igb_ptp_adjtime_i210;
 		adapter->ptp_caps.gettime64 = igb_ptp_gettime_i210;
 		adapter->ptp_caps.settime64 = igb_ptp_settime_i210;
diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
index 7a240fce3a7ea0..e2460a57e4b110 100644
--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -375,7 +375,7 @@ static int periodic_output(struct dp83640_clock *clock,
 
 /* ptp clock methods */
 
-static int ptp_dp83640_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
+static int ptp_dp83640_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 {
 	struct dp83640_clock *clock =
 		container_of(ptp, struct dp83640_clock, caps);
@@ -384,13 +384,13 @@ static int ptp_dp83640_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 	int neg_adj = 0;
 	u16 hi, lo;
 
-	if (ppb < 0) {
+	if (scaled_ppm < 0) {
 		neg_adj = 1;
-		ppb = -ppb;
+		scaled_ppm = -scaled_ppm;
 	}
-	rate = ppb;
-	rate <<= 26;
-	rate = div_u64(rate, 1953125);
+	rate = scaled_ppm;
+	rate <<= 13;
+	rate = div_u64(rate, 15625);
 
 	hi = (rate >> 16) & PTP_RATE_HI_MASK;
 	if (neg_adj)
@@ -1035,7 +1035,7 @@ static void dp83640_clock_init(struct dp83640_clock *clock, struct mii_bus *bus)
 	clock->caps.n_per_out	= N_PER_OUT;
 	clock->caps.n_pins	= DP83640_N_PINS;
 	clock->caps.pps		= 0;
-	clock->caps.adjfreq	= ptp_dp83640_adjfreq;
+	clock->caps.adjfine	= ptp_dp83640_adjfine;
 	clock->caps.adjtime	= ptp_dp83640_adjtime;
 	clock->caps.gettime64	= ptp_dp83640_gettime;
 	clock->caps.settime64	= ptp_dp83640_settime;
diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index 86280b7e41f3f7..9c13381b69662c 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -153,7 +153,10 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct timex *tx)
 		s32 ppb = scaled_ppm_to_ppb(tx->freq);
 		if (ppb > ops->max_adj || ppb < -ops->max_adj)
 			return -ERANGE;
-		err = ops->adjfreq(ops, ppb);
+		if (ops->adjfine)
+			err = ops->adjfine(ops, tx->freq);
+		else
+			err = ops->adjfreq(ops, ppb);
 		ptp->dialed_frequency = tx->freq;
 	} else if (tx->modes == 0) {
 		tx->freq = ptp->dialed_frequency;
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 5ad54fc66cf0f5..b76d47aba564ff 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -58,7 +58,14 @@ struct system_device_crosststamp;
  *
  * clock operations
  *
+ * @adjfine:  Adjusts the frequency of the hardware clock.
+ *            parameter scaled_ppm: Desired frequency offset from
+ *            nominal frequency in parts per million, but with a
+ *            16 bit binary fractional field.
+ *
  * @adjfreq:  Adjusts the frequency of the hardware clock.
+ *            This method is deprecated.  New drivers should implement
+ *            the @adjfine method instead.
  *            parameter delta: Desired frequency offset from nominal frequency
  *            in parts per billion
  *
@@ -108,6 +115,7 @@ struct ptp_clock_info {
 	int n_pins;
 	int pps;
 	struct ptp_pin_desc *pin_config;
+	int (*adjfine)(struct ptp_clock_info *ptp, long scaled_ppm);
 	int (*adjfreq)(struct ptp_clock_info *ptp, s32 delta);
 	int (*adjtime)(struct ptp_clock_info *ptp, s64 delta);
 	int (*gettime64)(struct ptp_clock_info *ptp, struct timespec64 *ts);