net: dsa: sja1105: Add support for the PTP clock

The design of this PHC driver is influenced by the switch's behavior
w.r.t. timestamping.  It exposes two PTP counters, one free-running
(PTPTSCLK) and the other offset- and frequency-corrected in hardware
through PTPCLKVAL, PTPCLKADD and PTPCLKRATE.  The MACs can sample either
of these for frame timestamps.

However, the user manual warns that taking timestamps based on the
corrected clock is less than useful, as the switch can deliver corrupted
timestamps in a variety of circumstances.

Therefore, this PHC uses the free-running PTPTSCLK together with a
timecounter/cyclecounter structure that translates it into a software
time domain.  Thus, the settime/adjtime and adjfine callbacks are
hardware no-ops.

The timestamps (introduced in a further patch) will also be translated
to the correct time domain before being handed over to the userspace PTP
stack.

The introduction of a second set of PHC operations that operate on the
hardware PTPCLKVAL/PTPCLKADD/PTPCLKRATE in the future is somewhat
unavoidable, as the TTEthernet core uses the corrected PTP time domain.
However, the free-running counter + timecounter structure combination
will suffice for now, as the resulting timestamps yield a sub-50 ns
synchronization offset in steady state using linuxptp.

For this patch, in absence of frame timestamping, the operations of the
switch PHC were tested by syncing it to the system time as a local slave
clock with:

phc2sys -s CLOCK_REALTIME -c swp2 -O 0 -m -S 0.01

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/net/dsa/sja1105/sja1105.h b/drivers/net/dsa/sja1105/sja1105.h
index 61d00682de60..3c6296203c21 100644
--- a/drivers/net/dsa/sja1105/sja1105.h
+++ b/drivers/net/dsa/sja1105/sja1105.h
@@ -5,6 +5,8 @@
 #ifndef _SJA1105_H
 #define _SJA1105_H
 
+#include <linux/ptp_clock_kernel.h>
+#include <linux/timecounter.h>
 #include <linux/dsa/sja1105.h>
 #include <net/dsa.h>
 #include <linux/mutex.h>
@@ -27,6 +29,10 @@ struct sja1105_regs {
 	u64 rgu;
 	u64 config;
 	u64 rmii_pll1;
+	u64 ptp_control;
+	u64 ptpclk;
+	u64 ptpclkrate;
+	u64 ptptsclk;
 	u64 pad_mii_tx[SJA1105_NUM_PORTS];
 	u64 cgu_idiv[SJA1105_NUM_PORTS];
 	u64 rgmii_pad_mii_tx[SJA1105_NUM_PORTS];
@@ -53,6 +59,7 @@ struct sja1105_info {
 	const struct sja1105_dynamic_table_ops *dyn_ops;
 	const struct sja1105_table_ops *static_ops;
 	const struct sja1105_regs *regs;
+	int (*ptp_cmd)(const void *ctx, const void *data);
 	int (*reset_cmd)(const void *ctx, const void *data);
 	int (*setup_rgmii_delay)(const void *ctx, int port);
 	/* Prototypes from include/net/dsa.h */
@@ -72,6 +79,16 @@ struct sja1105_private {
 	struct spi_device *spidev;
 	struct dsa_switch *ds;
 	struct sja1105_port ports[SJA1105_NUM_PORTS];
+	struct ptp_clock_info ptp_caps;
+	struct ptp_clock *clock;
+	/* The cycle counter translates the PTP timestamps (based on
+	 * a free-running counter) into a software time domain.
+	 */
+	struct cyclecounter tstamp_cc;
+	struct timecounter tstamp_tc;
+	struct delayed_work refresh_work;
+	/* Serializes all operations on the cycle counter */
+	struct mutex ptp_lock;
 	/* Serializes transmission of management frames so that
 	 * the switch doesn't confuse them with one another.
 	 */
@@ -79,6 +96,7 @@ struct sja1105_private {
 };
 
 #include "sja1105_dynamic_config.h"
+#include "sja1105_ptp.h"
 
 struct sja1105_spi_message {
 	u64 access;