Support ptp physical/virtual clocks conversion via sysfs.
There will be a new attribute n_vclocks under ptp physical
clock sysfs.

- In default, the value is 0 meaning only ptp physical clock
  is in use.
- Setting the value can create corresponding number of ptp
  virtual clocks to use. But current physical clock is guaranteed
  to stay free running.
- Setting the value back to 0 can delete virtual clocks and back
  use physical clock again.

Another new attribute max_vclocks control the maximum number of
ptp vclocks.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
---
Changes for v2:
	- Split from v1 patch #2.
	- Converted to num_vclocks for creating virtual clocks.
	- Guranteed physical clock free running when using virtual
	  clocks.
	- Fixed build warning.
	- Updated copyright.
Changes for v3:
	- Protected concurrency of ptp->num_vclocks accessing.
Changes for v4:
	- Rephrased description in doc.
	- Used unsigned int for vclocks number, and max_vclocks
	  for limitiation.
	- Fixed mutex locking.
	- Other minor fixes.
Changes for v5:
	- Fixed checkpatch.
	- Checked pointer parent->class->name.
---
 Documentation/ABI/testing/sysfs-ptp |  20 ++++
 drivers/ptp/ptp_clock.c             |  26 ++++++
 drivers/ptp/ptp_private.h           |  21 +++++
 drivers/ptp/ptp_sysfs.c             | 138 ++++++++++++++++++++++++++++
 4 files changed, 205 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-ptp b/Documentation/ABI/testing/sysfs-ptp
index 2363ad810ddb..d378f57c1b73 100644
--- a/Documentation/ABI/testing/sysfs-ptp
+++ b/Documentation/ABI/testing/sysfs-ptp

@@ -33,6 +33,13 @@ Description:
 		frequency adjustment value (a positive integer) in
 		parts per billion.
 
+What:		/sys/class/ptp/ptpN/max_vclocks
+Date:		May 2021
+Contact:	Yangbo Lu <yangbo.lu@nxp.com>
+Description:
+		This file contains the maximum number of ptp vclocks.
+		Write integer to re-configure it.
+
 What:		/sys/class/ptp/ptpN/n_alarms
 Date:		September 2010
 Contact:	Richard Cochran <richardcochran@gmail.com>

@@ -61,6 +68,19 @@ Description:
 		This file contains the number of programmable pins
 		offered by the PTP hardware clock.
 
+What:		/sys/class/ptp/ptpN/n_vclocks
+Date:		May 2021
+Contact:	Yangbo Lu <yangbo.lu@nxp.com>
+Description:
+		This file contains the number of virtual PTP clocks in
+		use.  By default, the value is 0 meaning that only the
+		physical clock is in use.  Setting the value creates
+		the corresponding number of virtual clocks and causes
+		the physical clock to become free running.  Setting the
+		value back to 0 deletes the virtual clocks and
+		switches the physical clock back to normal, adjustable
+		operation.
+
 What:		/sys/class/ptp/ptpN/pins
 Date:		March 2014
 Contact:	Richard Cochran <richardcochran@gmail.com>

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index a23a37a4d5dc..7334f478dde7 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c

@@ -76,6 +76,11 @@ static int ptp_clock_settime(struct posix_clock *pc, const struct timespec64 *tp
 {
 	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
 
+	if (ptp_vclock_in_use(ptp)) {
+		pr_err("ptp: virtual clock in use\n");
+		return -EBUSY;
+	}
+
 	return  ptp->info->settime64(ptp->info, tp);
 }
 

@@ -97,6 +102,11 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
 	struct ptp_clock_info *ops;
 	int err = -EOPNOTSUPP;
 
+	if (ptp_vclock_in_use(ptp)) {
+		pr_err("ptp: virtual clock in use\n");
+		return -EBUSY;
+	}
+
 	ops = ptp->info;
 
 	if (tx->modes & ADJ_SETOFFSET) {

@@ -161,6 +171,7 @@ static void ptp_clock_release(struct device *dev)
 	ptp_cleanup_pin_groups(ptp);
 	mutex_destroy(&ptp->tsevq_mux);
 	mutex_destroy(&ptp->pincfg_mux);
+	mutex_destroy(&ptp->n_vclocks_mux);
 	ida_simple_remove(&ptp_clocks_map, ptp->index);
 	kfree(ptp);
 }

@@ -208,6 +219,7 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	spin_lock_init(&ptp->tsevq.lock);
 	mutex_init(&ptp->tsevq_mux);
 	mutex_init(&ptp->pincfg_mux);
+	mutex_init(&ptp->n_vclocks_mux);
 	init_waitqueue_head(&ptp->tsev_wq);
 
 	if (ptp->info->do_aux_work) {

@@ -221,6 +233,14 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 		ptp->pps_source->lookup_cookie = ptp;
 	}
 
+	/* PTP virtual clock is being registered under physical clock */
+	if (parent->class && parent->class->name &&
+	    strcmp(parent->class->name, "ptp") == 0)
+		ptp->is_virtual_clock = true;
+
+	if (!ptp->is_virtual_clock)
+		ptp->max_vclocks = PTP_DEFAULT_MAX_VCLOCKS;
+
 	err = ptp_populate_pin_groups(ptp);
 	if (err)
 		goto no_pin_groups;

@@ -270,6 +290,7 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 kworker_err:
 	mutex_destroy(&ptp->tsevq_mux);
 	mutex_destroy(&ptp->pincfg_mux);
+	mutex_destroy(&ptp->n_vclocks_mux);
 	ida_simple_remove(&ptp_clocks_map, index);
 no_slot:
 	kfree(ptp);

@@ -280,6 +301,11 @@ EXPORT_SYMBOL(ptp_clock_register);
 
 int ptp_clock_unregister(struct ptp_clock *ptp)
 {
+	if (ptp_vclock_in_use(ptp)) {
+		pr_err("ptp: virtual clock in use\n");
+		return -EBUSY;
+	}
+