[PATCH net-next v1 1/6] ptp: Add cycles support for virtual clocks

[Gerhard Engleder <gerhard@engleder-embedded.com>]

ptp vclocks require a free running time for their timecounter.
Currently only a physical clock forced to free running is supported.
If vclocks are used, then the physical clock cannot be synchronized
anymore. The synchronized time is not available in hardware in this
case. As a result, timed transmission with TAPRIO hardware support
is not possible anymore.

If hardware would support a free running time additionally to the
physical clock, then the physical clock does not need to be forced to
free running. Thus, the physical clocks can still be synchronized
while vclocks are in use.

The physical clock could be used to synchronize the time domain of the
TSN network and trigger TAPRIO. In parallel vclocks can be used to
synchronize other time domains.

Introduce support for a free running time called cycles to physical
clocks. Rework ptp vclocks to use cycles. Default implementation of
cycles is based on time of physical clock. Thus, behavior of ptp vclocks
based on physical clocks without cycles is identical to previous
behavior.

Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
---
 drivers/ptp/ptp_clock.c          | 31 +++++++++++++++++++++++++++----
 drivers/ptp/ptp_private.h        | 10 ++++++++++
 drivers/ptp/ptp_sysfs.c          | 10 ++++++----
 drivers/ptp/ptp_vclock.c         | 13 +++++--------
 include/linux/ptp_clock_kernel.h | 30 ++++++++++++++++++++++++++++++
 5 files changed, 78 insertions(+), 16 deletions(-)

diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index b6f2cfd15dd2..54b9f54ac0b2 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -77,8 +77,8 @@ 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");
+	if (ptp_clock_freerun(ptp)) {
+		pr_err("ptp: physical clock is free running\n");
 		return -EBUSY;
 	}
 
@@ -103,8 +103,8 @@ 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");
+	if (ptp_clock_freerun(ptp)) {
+		pr_err("ptp: physical clock is free running\n");
 		return -EBUSY;
 	}
 
@@ -178,6 +178,14 @@ static void ptp_clock_release(struct device *dev)
 	kfree(ptp);
 }
 
+static int ptp_getcycles64(struct ptp_clock_info *info, struct timespec64 *ts)
+{
+	if (info->getcyclesx64)
+		return info->getcyclesx64(info, ts, NULL);
+	else
+		return info->gettime64(info, ts);
+}
+
 static void ptp_aux_kworker(struct kthread_work *work)
 {
 	struct ptp_clock *ptp = container_of(work, struct ptp_clock,
@@ -225,6 +233,21 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	mutex_init(&ptp->n_vclocks_mux);
 	init_waitqueue_head(&ptp->tsev_wq);
 
+	if (!ptp->info->getcycles64 && !ptp->info->getcyclesx64) {
+		/* Cycles are based on time per default. */
+		ptp->info->getcycles64 = ptp_getcycles64;
+
+		if (ptp->info->gettimex64)
+			ptp->info->getcyclesx64 = ptp->info->gettimex64;
+
+		if (ptp->info->getcrosststamp)
+			ptp->info->getcrosscycles = ptp->info->getcrosststamp;
+	} else {
+		ptp->cycles = true;
+		if (!ptp->info->getcycles64 && ptp->info->getcyclesx64)
+			ptp->info->getcycles64 = ptp_getcycles64;
+	}
+
 	if (ptp->info->do_aux_work) {
 		kthread_init_delayed_work(&ptp->aux_work, ptp_aux_kworker);
 		ptp->kworker = kthread_create_worker(0, "ptp%d", ptp->index);
diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
index dba6be477067..ae66376def84 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h
@@ -52,6 +52,7 @@ struct ptp_clock {
 	int *vclock_index;
 	struct mutex n_vclocks_mux; /* protect concurrent n_vclocks access */
 	bool is_virtual_clock;
+	bool cycles;
 };
 
 #define info_to_vclock(d) container_of((d), struct ptp_vclock, info)
@@ -96,6 +97,15 @@ static inline bool ptp_vclock_in_use(struct ptp_clock *ptp)
 	return in_use;
 }
 
+/* Check if ptp clock shall be free running */
+static inline bool ptp_clock_freerun(struct ptp_clock *ptp)
+{
+	if (ptp->cycles)
+		return false;
+
+	return ptp_vclock_in_use(ptp);
+}
+
 extern struct class *ptp_class;
 
 /*
diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c
index 9233bfedeb17..8da3d374f78e 100644
--- a/drivers/ptp/ptp_sysfs.c
+++ b/drivers/ptp/ptp_sysfs.c
@@ -231,10 +231,12 @@ static ssize_t n_vclocks_store(struct device *dev,
 			*(ptp->vclock_index + ptp->n_vclocks - i) = -1;
 	}
 
-	if (num == 0)
-		dev_info(dev, "only physical clock in use now\n");
-	else
-		dev_info(dev, "guarantee physical clock free running\n");
+	if (!ptp->cycles) {
+		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);
diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c
index cb179a3ea508..3a095eab9cc5 100644
--- a/drivers/ptp/ptp_vclock.c
+++ b/drivers/ptp/ptp_vclock.c
@@ -68,7 +68,7 @@ static int ptp_vclock_gettimex(struct ptp_clock_info *ptp,
 	int err;
 	u64 ns;
 
-	err = pptp->info->gettimex64(pptp->info, &pts, sts);
+	err = pptp->info->getcyclesx64(pptp->info, &pts, sts);
 	if (err)
 		return err;
 
@@ -104,7 +104,7 @@ static int ptp_vclock_getcrosststamp(struct ptp_clock_info *ptp,
 	int err;
 	u64 ns;
 
-	err = pptp->info->getcrosststamp(pptp->info, xtstamp);
+	err = pptp->info->getcrosscycles(pptp->info, xtstamp);
 	if (err)
 		return err;
 
@@ -143,10 +143,7 @@ static u64 ptp_vclock_read(const struct cyclecounter *cc)
 	struct ptp_clock *ptp = vclock->pclock;
 	struct timespec64 ts = {};
 
-	if (ptp->info->gettimex64)
-		ptp->info->gettimex64(ptp->info, &ts, NULL);
-	else
-		ptp->info->gettime64(ptp->info, &ts);
+	ptp->info->getcycles64(ptp->info, &ts);
 
 	return timespec64_to_ns(&ts);
 }
@@ -168,11 +165,11 @@ struct ptp_vclock *ptp_vclock_register(struct ptp_clock *pclock)
 
 	vclock->pclock = pclock;
 	vclock->info = ptp_vclock_info;
-	if (pclock->info->gettimex64)
+	if (pclock->info->getcyclesx64)
 		vclock->info.gettimex64 = ptp_vclock_gettimex;
 	else
 		vclock->info.gettime64 = ptp_vclock_gettime;
-	if (pclock->info->getcrosststamp)
+	if (pclock->info->getcrosscycles)
 		vclock->info.getcrosststamp = ptp_vclock_getcrosststamp;
 	vclock->cc = ptp_vclock_cc;
 
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 554454cb8693..acdcaa4a1ec2 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -108,6 +108,31 @@ struct ptp_system_timestamp {
  * @settime64:  Set the current time on the hardware clock.
  *              parameter ts: Time value to set.
  *
+ * @getcycles64:  Reads the current free running time from the hardware clock.
+ *                If @getcycles64 and @getcyclesx64 are not supported, then
+ *                @gettime64 or @gettimex64 will be used as default
+ *                implementation.
+ *                parameter ts: Holds the result.
+ *
+ * @getcyclesx64:  Reads the current free running time from the hardware clock
+ *                 and optionally also the system clock.
+ *                 If @getcycles64 and @getcyclesx64 are not supported, then
+ *                 @gettimex64 will be used as default implementation if
+ *                 available.
+ *                 parameter ts: Holds the PHC timestamp.
+ *                 parameter sts: If not NULL, it holds a pair of timestamps
+ *                 from the system clock. The first reading is made right before
+ *                 reading the lowest bits of the PHC timestamp and the second
+ *                 reading immediately follows that.
+ *
+ * @getcrosscycles:  Reads the current free running time from the hardware clock
+ *                   and system clock simultaneously.
+ *                   If @getcycles64 and @getcyclesx64 are not supported, then
+ *                   @getcrosststamp will be used as default implementation if
+ *                   available.
+ *                   parameter cts: Contains timestamp (device,system) pair,
+ *                   where system time is realtime and monotonic.
+ *
  * @enable:   Request driver to enable or disable an ancillary feature.
  *            parameter request: Desired resource to enable or disable.
  *            parameter on: Caller passes one to enable or zero to disable.
@@ -155,6 +180,11 @@ struct ptp_clock_info {
 	int (*getcrosststamp)(struct ptp_clock_info *ptp,
 			      struct system_device_crosststamp *cts);
 	int (*settime64)(struct ptp_clock_info *p, const struct timespec64 *ts);
+	int (*getcycles64)(struct ptp_clock_info *ptp, struct timespec64 *ts);
+	int (*getcyclesx64)(struct ptp_clock_info *ptp, struct timespec64 *ts,
+			    struct ptp_system_timestamp *sts);
+	int (*getcrosscycles)(struct ptp_clock_info *ptp,
+			      struct system_device_crosststamp *cts);
 	int (*enable)(struct ptp_clock_info *ptp,
 		      struct ptp_clock_request *request, int on);
 	int (*verify)(struct ptp_clock_info *ptp, unsigned int pin,
-- 
2.20.1