RE: [net-next, v3, 02/10] ptp: support ptp physical/virtual clocks conversion

Hi Richard,

-----Original Message-----
From: Richard Cochran <richardcochran@gmail.com>
Sent: 2021年6月19日 12:06
To: Y.b. Lu <yangbo.lu@nxp.com>
Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
linux-kselftest@vger.kernel.org; mptcp@lists.linux.dev; David S . Miller
[off-list ref]; Jakub Kicinski [off-list ref]; Mat Martineau
[off-list ref]; Matthieu Baerts
[off-list ref]; Shuah Khan [off-list ref]; Michal
Kubecek [off-list ref]; Florian Fainelli [off-list ref];
Andrew Lunn [off-list ref]; Rui Sousa [off-list ref]; Sebastien
Laveze [off-list ref]
Subject: Re: [net-next, v3, 02/10] ptp: support ptp physical/virtual clocks
conversion

On Tue, Jun 15, 2021 at 05:45:09PM +0800, Yangbo Lu wrote:

quoted

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c index

a780435331c8..78414b3e16dd 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_guaranteed_pclock(ptp)) {

Can we please invent a more descriptive name for this method?
The word "guaranteed" suggests much more.

quoted

+		pr_err("ptp: virtual clock in use, guarantee physical clock free
+running\n");

This is good:           ^^^^^^^^^^^^^^^^^^^^^^^^^
You can drop this part:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

So, please rename ptp_guaranteed_pclock() to ptp_vclock_in_use();

Thank you. Will convert to that.

quoted

+		return -EBUSY;
+	}
+
 	return  ptp->info->settime64(ptp->info, tp);  }

quoted

diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
index 3f388d63904c..6949afc9d733 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h

@@ -46,6 +46,9 @@ struct ptp_clock {
 	const struct attribute_group *pin_attr_groups[2];
 	struct kthread_worker *kworker;
 	struct kthread_delayed_work aux_work;
+	u8 n_vclocks;

Why not use "unsigned int" type?  I don't see a need to set an artificial limit.

Please see my explain in another email thread. Thanks.

quoted

+	struct mutex n_vclocks_mux; /* protect concurrent n_vclocks access */
+	bool vclock_flag;

"flag" is vague.  How about "is_virtual_clock" instead?

That's better. Will use it. Thank you.

quoted

 };

 #define info_to_vclock(d) container_of((d), struct ptp_vclock, info)

@@ -75,6 +78,18 @@ static inline int queue_cnt(struct

timestamp_event_queue *q)

quoted

 	return cnt < 0 ? PTP_MAX_TIMESTAMPS + cnt : cnt;  }

+/*
+ * Guarantee physical clock to stay free running, if ptp virtual
+clocks
+ * on it are in use.
+ */
+static inline bool ptp_guaranteed_pclock(struct ptp_clock *ptp) {
+	if (!ptp->vclock_flag && ptp->n_vclocks)

Need to take mutex for n_vclocks to prevent load tearing.

quoted

+		return true;
+
+	return false;
+}
+
 /*
  * see ptp_chardev.c
  */

quoted

@@ -148,6 +149,90 @@ static ssize_t pps_enable_store(struct device

*dev,  }  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);
+
+	return snprintf(page, PAGE_SIZE-1, "%d\n", ptp->n_vclocks);

Take mutex.

Will take mutex everywhere to access it.

quoted

+}
+
+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;
+	u8 num, i;
+
+	if (kstrtou8(buf, 0, &num))
+		goto out;
+
+	if (num > PTP_MAX_VCLOCKS) {
+		dev_err(dev, "max value is %d\n", PTP_MAX_VCLOCKS);
+		goto out;
+	}
+
+	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
+		return -ERESTARTSYS;
+
+	/* 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) {
+				mutex_unlock(&ptp->n_vclocks_mux);
+				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:
+	return err;
+}
+static DEVICE_ATTR_RW(n_vclocks);
+
 static struct attribute *ptp_attrs[] = {
 	&dev_attr_clock_name.attr,

quoted

diff --git a/include/uapi/linux/ptp_clock.h

b/include/uapi/linux/ptp_clock.h index 1d108d597f66..4b933dc1b81b
100644

--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h

@@ -69,6 +69,11 @@
  */
 #define PTP_PEROUT_V1_VALID_FLAGS	(0)

+/*
+ * Max number of PTP virtual clocks per PTP physical clock  */
+#define PTP_MAX_VCLOCKS			20

Why limit this to twenty clocks?

Please see my explain in another email thread. Thanks.

Thanks,
Richard