ptp: add ptp virtual clock driver framework

This patch is to add ptp virtual clock driver framework
utilizing timecounter/cyclecounter.

The patch just exports two essential APIs for PTP driver.

- ptp_vclock_register()
- ptp_vclock_unregister()

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

drivers/ptp/Makefile

···
 # Makefile for PTP 1588 clock support.
 #
 
-ptp-y					:= ptp_clock.o ptp_chardev.o ptp_sysfs.o
+ptp-y					:= ptp_clock.o ptp_chardev.o ptp_sysfs.o ptp_vclock.o
 ptp_kvm-$(CONFIG_X86)			:= ptp_kvm_x86.o ptp_kvm_common.o
 ptp_kvm-$(CONFIG_HAVE_ARM_SMCCC)	:= ptp_kvm_arm.o ptp_kvm_common.o
 obj-$(CONFIG_PTP_1588_CLOCK)		+= ptp.o

drivers/ptp/ptp_private.h

···
 	struct kthread_delayed_work aux_work;
 };
 
+#define info_to_vclock(d) container_of((d), struct ptp_vclock, info)
+#define cc_to_vclock(d) container_of((d), struct ptp_vclock, cc)
+#define dw_to_vclock(d) container_of((d), struct ptp_vclock, refresh_work)
+
+struct ptp_vclock {
+	struct ptp_clock *pclock;
+	struct ptp_clock_info info;
+	struct ptp_clock *clock;
+	struct cyclecounter cc;
+	struct timecounter tc;
+	spinlock_t lock;	/* protects tc/cc */
+};
+
 /*
  * The function queue_cnt() is safe for readers to call without
  * holding q->lock. Readers use this function to verify that the queue
···
 int ptp_populate_pin_groups(struct ptp_clock *ptp);
 void ptp_cleanup_pin_groups(struct ptp_clock *ptp);
 
+struct ptp_vclock *ptp_vclock_register(struct ptp_clock *pclock);
+void ptp_vclock_unregister(struct ptp_vclock *vclock);
 #endif

drivers/ptp/ptp_vclock.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * PTP virtual clock driver
+ *
+ * Copyright 2021 NXP
+ */
+#include <linux/slab.h>
+#include "ptp_private.h"
+
+#define PTP_VCLOCK_CC_SHIFT		31
+#define PTP_VCLOCK_CC_MULT		(1 << PTP_VCLOCK_CC_SHIFT)
+#define PTP_VCLOCK_FADJ_SHIFT		9
+#define PTP_VCLOCK_FADJ_DENOMINATOR	15625ULL
+#define PTP_VCLOCK_REFRESH_INTERVAL	(HZ * 2)
+
+static int ptp_vclock_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
+{
+	struct ptp_vclock *vclock = info_to_vclock(ptp);
+	unsigned long flags;
+	s64 adj;
+
+	adj = (s64)scaled_ppm << PTP_VCLOCK_FADJ_SHIFT;
+	adj = div_s64(adj, PTP_VCLOCK_FADJ_DENOMINATOR);
+
+	spin_lock_irqsave(&vclock->lock, flags);
+	timecounter_read(&vclock->tc);
+	vclock->cc.mult = PTP_VCLOCK_CC_MULT + adj;
+	spin_unlock_irqrestore(&vclock->lock, flags);
+
+	return 0;
+}
+
+static int ptp_vclock_adjtime(struct ptp_clock_info *ptp, s64 delta)
+{
+	struct ptp_vclock *vclock = info_to_vclock(ptp);
+	unsigned long flags;
+
+	spin_lock_irqsave(&vclock->lock, flags);
+	timecounter_adjtime(&vclock->tc, delta);
+	spin_unlock_irqrestore(&vclock->lock, flags);
+
+	return 0;
+}
+
+static int ptp_vclock_gettime(struct ptp_clock_info *ptp,
+			      struct timespec64 *ts)
+{
+	struct ptp_vclock *vclock = info_to_vclock(ptp);
+	unsigned long flags;
+	u64 ns;
+
+	spin_lock_irqsave(&vclock->lock, flags);
+	ns = timecounter_read(&vclock->tc);
+	spin_unlock_irqrestore(&vclock->lock, flags);
+	*ts = ns_to_timespec64(ns);
+
+	return 0;
+}
+
+static int ptp_vclock_settime(struct ptp_clock_info *ptp,
+			      const struct timespec64 *ts)
+{
+	struct ptp_vclock *vclock = info_to_vclock(ptp);
+	u64 ns = timespec64_to_ns(ts);
+	unsigned long flags;
+
+	spin_lock_irqsave(&vclock->lock, flags);
+	timecounter_init(&vclock->tc, &vclock->cc, ns);
+	spin_unlock_irqrestore(&vclock->lock, flags);
+
+	return 0;
+}
+
+static long ptp_vclock_refresh(struct ptp_clock_info *ptp)
+{
+	struct ptp_vclock *vclock = info_to_vclock(ptp);
+	struct timespec64 ts;
+
+	ptp_vclock_gettime(&vclock->info, &ts);
+
+	return PTP_VCLOCK_REFRESH_INTERVAL;
+}
+
+static const struct ptp_clock_info ptp_vclock_info = {
+	.owner		= THIS_MODULE,
+	.name		= "ptp virtual clock",
+	/* The maximum ppb value that long scaled_ppm can support */
+	.max_adj	= 32767999,
+	.adjfine	= ptp_vclock_adjfine,
+	.adjtime	= ptp_vclock_adjtime,
+	.gettime64	= ptp_vclock_gettime,
+	.settime64	= ptp_vclock_settime,
+	.do_aux_work	= ptp_vclock_refresh,
+};
+
+static u64 ptp_vclock_read(const struct cyclecounter *cc)
+{
+	struct ptp_vclock *vclock = cc_to_vclock(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);
+
+	return timespec64_to_ns(&ts);
+}
+
+static const struct cyclecounter ptp_vclock_cc = {
+	.read	= ptp_vclock_read,
+	.mask	= CYCLECOUNTER_MASK(32),
+	.mult	= PTP_VCLOCK_CC_MULT,
+	.shift	= PTP_VCLOCK_CC_SHIFT,
+};
+
+struct ptp_vclock *ptp_vclock_register(struct ptp_clock *pclock)
+{
+	struct ptp_vclock *vclock;
+
+	vclock = kzalloc(sizeof(*vclock), GFP_KERNEL);
+	if (!vclock)
+		return NULL;
+
+	vclock->pclock = pclock;
+	vclock->info = ptp_vclock_info;
+	vclock->cc = ptp_vclock_cc;
+
+	snprintf(vclock->info.name, PTP_CLOCK_NAME_LEN, "ptp%d_virt",
+		 pclock->index);
+
+	spin_lock_init(&vclock->lock);
+
+	vclock->clock = ptp_clock_register(&vclock->info, &pclock->dev);
+	if (IS_ERR_OR_NULL(vclock->clock)) {
+		kfree(vclock);
+		return NULL;
+	}
+
+	timecounter_init(&vclock->tc, &vclock->cc, 0);
+	ptp_schedule_worker(vclock->clock, PTP_VCLOCK_REFRESH_INTERVAL);
+
+	return vclock;
+}
+
+void ptp_vclock_unregister(struct ptp_vclock *vclock)
+{
+	ptp_clock_unregister(vclock->clock);
+	kfree(vclock);
+}

include/linux/ptp_clock_kernel.h

···
 #include <linux/device.h>
 #include <linux/pps_kernel.h>
 #include <linux/ptp_clock.h>
+#include <linux/timecounter.h>
 
+#define PTP_CLOCK_NAME_LEN	32
 /**
  * struct ptp_clock_request - request PTP clock event
  *
···
 
 struct ptp_clock_info {
 	struct module *owner;
-	char name[16];
+	char name[PTP_CLOCK_NAME_LEN];
 	s32 max_adj;
 	int n_alarm;
 	int n_ext_ts;