ptp: support ptp physical/virtual clocks conversion

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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/ABI/testing/sysfs-ptp

···
 		frequency adjustment value (a positive integer) in
 		parts per billion.
 
+What:		/sys/class/ptp/ptpN/max_vclocks
+Date:		May 2021
+Contact:	Yangbo Lu <[e-mail]>
+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 <[e-mail]>
···
 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 <[e-mail]>
+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

drivers/ptp/ptp_clock.c

···
 {
 	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);
 }
 
···
 	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
 	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;
 
···
 	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);
 }
···
 	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) {
···
 		}
 		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)
···
 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);
···
 
 int ptp_clock_unregister(struct ptp_clock *ptp)
 {
+	if (ptp_vclock_in_use(ptp)) {
+		pr_err("ptp: virtual clock in use\n");
+		return -EBUSY;
+	}
+
 	ptp->defunct = 1;
 	wake_up_interruptible(&ptp->tsev_wq);
 

drivers/ptp/ptp_private.h

···
 
 #define PTP_MAX_TIMESTAMPS 128
 #define PTP_BUF_TIMESTAMPS 30
+#define PTP_DEFAULT_MAX_VCLOCKS 20
 
 struct timestamp_event_queue {
 	struct ptp_extts_event buf[PTP_MAX_TIMESTAMPS];
···
 	const struct attribute_group *pin_attr_groups[2];
 	struct kthread_worker *kworker;
 	struct kthread_delayed_work aux_work;
+	unsigned int max_vclocks;
+	unsigned int n_vclocks;
+	struct mutex n_vclocks_mux; /* protect concurrent n_vclocks access */
+	bool is_virtual_clock;
 };
 
 #define info_to_vclock(d) container_of((d), struct ptp_vclock, info)
···
 {
 	int cnt = q->tail - q->head;
 	return cnt < 0 ? PTP_MAX_TIMESTAMPS + cnt : cnt;
+}
+
+/* Check if ptp virtual clock is in use */
+static inline bool ptp_vclock_in_use(struct ptp_clock *ptp)
+{
+	bool in_use = false;
+
+	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
+		return true;
+
+	if (!ptp->is_virtual_clock && ptp->n_vclocks)
+		in_use = true;
+
+	mutex_unlock(&ptp->n_vclocks_mux);
+
+	return in_use;
 }
 
 /*

drivers/ptp/ptp_sysfs.c

···
  * PTP 1588 clock support - sysfs interface.
  *
  * Copyright (C) 2010 OMICRON electronics GmbH
+ * Copyright 2021 NXP
  */
 #include <linux/capability.h>
 #include <linux/slab.h>
···
 }
 static DEVICE_ATTR(pps_enable, 0220, NULL, pps_enable_store);
 
+static int unregister_vclock(struct device *dev, void *data)
+{
+	struct ptp_clock *ptp = dev_get_drvdata(dev);
+	struct ptp_clock_info *info = ptp->info;
+	struct ptp_vclock *vclock;
+	u8 *num = data;
+
+	vclock = info_to_vclock(info);
+	dev_info(dev->parent, "delete virtual clock ptp%d\n",
+		 vclock->clock->index);
+
+	ptp_vclock_unregister(vclock);
+	(*num)--;
+
+	/* For break. Not error. */
+	if (*num == 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+static ssize_t n_vclocks_show(struct device *dev,
+			      struct device_attribute *attr, char *page)
+{
+	struct ptp_clock *ptp = dev_get_drvdata(dev);
+	ssize_t size;
+
+	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
+		return -ERESTARTSYS;
+
+	size = snprintf(page, PAGE_SIZE - 1, "%d\n", ptp->n_vclocks);
+
+	mutex_unlock(&ptp->n_vclocks_mux);
+
+	return size;
+}
+
+static ssize_t n_vclocks_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	struct ptp_clock *ptp = dev_get_drvdata(dev);
+	struct ptp_vclock *vclock;
+	int err = -EINVAL;
+	u32 num, i;
+
+	if (kstrtou32(buf, 0, &num))
+		return err;
+
+	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
+		return -ERESTARTSYS;
+
+	if (num > ptp->max_vclocks) {
+		dev_err(dev, "max value is %d\n", ptp->max_vclocks);
+		goto out;
+	}
+
+	/* Need to create more vclocks */
+	if (num > ptp->n_vclocks) {
+		for (i = 0; i < num - ptp->n_vclocks; i++) {
+			vclock = ptp_vclock_register(ptp);
+			if (!vclock)
+				goto out;
+
+			dev_info(dev, "new virtual clock ptp%d\n",
+				 vclock->clock->index);
+		}
+	}
+
+	/* Need to delete vclocks */
+	if (num < ptp->n_vclocks) {
+		i = ptp->n_vclocks - num;
+		device_for_each_child_reverse(dev, &i,
+					      unregister_vclock);
+	}
+
+	if (num == 0)
+		dev_info(dev, "only physical clock in use now\n");
+	else
+		dev_info(dev, "guarantee physical clock free running\n");
+
+	ptp->n_vclocks = num;
+	mutex_unlock(&ptp->n_vclocks_mux);
+
+	return count;
+out:
+	mutex_unlock(&ptp->n_vclocks_mux);
+	return err;
+}
+static DEVICE_ATTR_RW(n_vclocks);
+
+static ssize_t max_vclocks_show(struct device *dev,
+				struct device_attribute *attr, char *page)
+{
+	struct ptp_clock *ptp = dev_get_drvdata(dev);
+	ssize_t size;
+
+	size = snprintf(page, PAGE_SIZE - 1, "%d\n", ptp->max_vclocks);
+
+	return size;
+}
+
+static ssize_t max_vclocks_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct ptp_clock *ptp = dev_get_drvdata(dev);
+	u32 max;
+
+	if (kstrtou32(buf, 0, &max) || max == 0)
+		return -EINVAL;
+
+	if (max == ptp->max_vclocks)
+		return count;
+
+	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
+		return -ERESTARTSYS;
+
+	if (max < ptp->n_vclocks) {
+		mutex_unlock(&ptp->n_vclocks_mux);
+		return -EINVAL;
+	}
+
+	ptp->max_vclocks = max;
+
+	mutex_unlock(&ptp->n_vclocks_mux);
+
+	return count;
+}
+static DEVICE_ATTR_RW(max_vclocks);
+
 static struct attribute *ptp_attrs[] = {
 	&dev_attr_clock_name.attr,
 
···
 	&dev_attr_fifo.attr,
 	&dev_attr_period.attr,
 	&dev_attr_pps_enable.attr,
+	&dev_attr_n_vclocks.attr,
+	&dev_attr_max_vclocks.attr,
 	NULL
 };
 
···
 			mode = 0;
 	} else if (attr == &dev_attr_pps_enable.attr) {
 		if (!info->pps)
+			mode = 0;
+	} else if (attr == &dev_attr_n_vclocks.attr ||
+		   attr == &dev_attr_max_vclocks.attr) {
+		if (ptp->is_virtual_clock)
 			mode = 0;
 	}