[PATCH v3 net-next 06/10] net: ptp: create a mock-up PTP Hardware Clock driver

Vladimir Oltean
2023-08-01T18:25:23Z

There are several cases where virtual net devices may benefit from
having a PTP clock, and these have to do with testing. I can see at
least netdevsim and veth as potential users of a common mock-up PTP
hardware clock driver.

The proposed idea is to create an object which emulates PTP clock
operations on top of the unadjustable CLOCK_MONOTONIC_RAW plus a
software-controlled time domain via a timecounter/cyclecounter and then
link that PHC to the netdevsim device.

The driver is fully functional for its intended purpose, and it
successfully passes the PTP selftests.

$ cd tools/testing/selftests/ptp/
$ ./phc.sh /dev/ptp2
TEST: settime [ OK ]
TEST: adjtime [ OK ]
TEST: adjfreq [ OK ]

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
v2->v3:
- split off ptp_mock into separate patch
- fix ptp_mock compilation as a module
- turn phc->lock into a global spinlock
- drop bogus support for ptp_clock_register() ever returning NULL
- add MAINTAINERS entry
v1->v2: patch is new

MAINTAINERS | 7 ++
drivers/ptp/Kconfig | 11 +++
drivers/ptp/Makefile | 1 +
drivers/ptp/ptp_mock.c | 175 +++++++++++++++++++++++++++++++++++++++
include/linux/ptp_mock.h | 38 +++++++++
5 files changed, 232 insertions(+)
create mode 100644 drivers/ptp/ptp_mock.c
create mode 100644 include/linux/ptp_mock.h

diff --git a/MAINTAINERS b/MAINTAINERS
index c4f95a9d03b9..164b7930f5d0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17175,6 +17175,13 @@ F: drivers/ptp/*
F: include/linux/ptp_cl*
K: (?:\b|_)ptp(?:\b|_)

+PTP MOCKUP CLOCK SUPPORT
+M: Vladimir Oltean <vladimir.oltean@nxp.com>
+L: netdev@vger.kernel.org
+S: Maintained
+F: drivers/ptp/ptp_mock.c
+F: include/linux/ptp_mock.h
+
PTP VIRTUAL CLOCK SUPPORT
M: Yangbo Lu <yangbo.lu@nxp.com>
L: netdev@vger.kernel.org
diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index 32dff1b4f891..ed9d97a032f1 100644
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -155,6 +155,17 @@ config PTP_1588_CLOCK_IDTCM
To compile this driver as a module, choose M here: the module
will be called ptp_clockmatrix.

+config PTP_1588_CLOCK_MOCK
+ tristate "Mock-up PTP clock"
+ depends on PTP_1588_CLOCK
+ help
+ This driver offers a set of PTP clock manipulation operations over
+ the system monotonic time. It can be used by virtual network device
+ drivers to emulate PTP capabilities.
+
+ To compile this driver as a module, choose M here: the module
+ will be called ptp_mock.
+
config PTP_1588_CLOCK_VMW
tristate "VMware virtual PTP clock"
depends on ACPI && HYPERVISOR_GUEST && X86
diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
index 553f18bf3c83..dea0cebd2303 100644
--- a/drivers/ptp/Makefile
+++ b/drivers/ptp/Makefile
@@ -16,6 +16,7 @@ ptp-qoriq-y += ptp_qoriq.o
ptp-qoriq-$(CONFIG_DEBUG_FS) += ptp_qoriq_debugfs.o
obj-$(CONFIG_PTP_1588_CLOCK_IDTCM) += ptp_clockmatrix.o
obj-$(CONFIG_PTP_1588_CLOCK_IDT82P33) += ptp_idt82p33.o
+obj-$(CONFIG_PTP_1588_CLOCK_MOCK) += ptp_mock.o
obj-$(CONFIG_PTP_1588_CLOCK_VMW) += ptp_vmw.o
obj-$(CONFIG_PTP_1588_CLOCK_OCP) += ptp_ocp.o
obj-$(CONFIG_PTP_DFL_TOD) += ptp_dfl_tod.o
diff --git a/drivers/ptp/ptp_mock.c b/drivers/ptp/ptp_mock.c
new file mode 100644
index 000000000000..1525aafca752
--- /dev/null
+++ b/drivers/ptp/ptp_mock.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2023 NXP
+ *
+ * Mock-up PTP Hardware Clock driver for virtual network devices
+ *
+ * Create a PTP clock which offers PTP time manipulation operations
+ * using a timecounter/cyclecounter on top of CLOCK_MONOTONIC_RAW.
+ */
+
+#include <linux/ptp_clock_kernel.h>
+#include <linux/ptp_mock.h>
+#include <linux/timecounter.h>
+
+/* Clamp scaled_ppm between -2,097,152,000 and 2,097,152,000,
+ * and thus "adj" between -68,719,476 and 68,719,476
+ */
+#define MOCK_PHC_MAX_ADJ_PPB 32000000
+/* Timestamps from ktime_get_raw() have 1 ns resolution, so the scale factor
+ * (MULT >> SHIFT) needs to be 1. Pick SHIFT as 31 bits, which translates
+ * MULT(freq 0) into 0x80000000.
+ */
+#define MOCK_PHC_CC_SHIFT 31
+#define MOCK_PHC_CC_MULT (1 << MOCK_PHC_CC_SHIFT)
+#define MOCK_PHC_FADJ_SHIFT 9
+#define MOCK_PHC_FADJ_DENOMINATOR 15625ULL
+
+/* The largest cycle_delta that timecounter_read_delta() can handle without a
+ * 64-bit overflow during the multiplication with cc->mult, given the max "adj"
+ * we permit, is ~8.3 seconds. Make sure readouts are more frequent than that.
+ */
+#define MOCK_PHC_REFRESH_INTERVAL (HZ * 5)
+
+#define info_to_phc(d) container_of((d), struct mock_phc, info)
+
+static DEFINE_SPINLOCK(mock_phc_lock);
+
+struct mock_phc {
+ struct ptp_clock_info info;
+ struct ptp_clock *clock;
+ struct timecounter tc;
+ struct cyclecounter cc;
+};
+
+static u64 mock_phc_cc_read(const struct cyclecounter *cc)
+{
+ return ktime_to_ns(ktime_get_raw());
+}
+
+static int mock_phc_adjfine(struct ptp_clock_info *info, long scaled_ppm)
+{
+ struct mock_phc *phc = info_to_phc(info);
+ s64 adj;
+
+ adj = (s64)scaled_ppm << MOCK_PHC_FADJ_SHIFT;
+ adj = div_s64(adj, MOCK_PHC_FADJ_DENOMINATOR);
+
+ spin_lock_bh(&mock_phc_lock);
+ timecounter_read(&phc->tc);
+ phc->cc.mult = MOCK_PHC_CC_MULT + adj;
+ spin_unlock_bh(&mock_phc_lock);
+
+ return 0;
+}
+
+static int mock_phc_adjtime(struct ptp_clock_info *info, s64 delta)
+{
+ struct mock_phc *phc = info_to_phc(info);
+
+ spin_lock_bh(&mock_phc_lock);
+ timecounter_adjtime(&phc->tc, delta);
+ spin_unlock_bh(&mock_phc_lock);
+
+ return 0;
+}
+
+static int mock_phc_settime64(struct ptp_clock_info *info,
+ const struct timespec64 *ts)
+{
+ struct mock_phc *phc = info_to_phc(info);
+ u64 ns = timespec64_to_ns(ts);
+
+ spin_lock_bh(&mock_phc_lock);
+ timecounter_init(&phc->tc, &phc->cc, ns);
+ spin_unlock_bh(&mock_phc_lock);
+
+ return 0;
+}
+
+static int mock_phc_gettime64(struct ptp_clock_info *info, struct timespec64 *ts)
+{
+ struct mock_phc *phc = info_to_phc(info);
+ u64 ns;
+
+ spin_lock_bh(&mock_phc_lock);
+ ns = timecounter_read(&phc->tc);
+ spin_unlock_bh(&mock_phc_lock);
+
+ *ts = ns_to_timespec64(ns);
+
+ return 0;
+}
+
+static long mock_phc_refresh(struct ptp_clock_info *info)
+{
+ struct timespec64 ts;
+
+ mock_phc_gettime64(info, &ts);
+
+ return MOCK_PHC_REFRESH_INTERVAL;
+}
+
+int mock_phc_index(struct mock_phc *phc)
+{
+ return ptp_clock_index(phc->clock);
+}
+EXPORT_SYMBOL_GPL(mock_phc_index);
+
+struct mock_phc *mock_phc_create(struct device *dev)
+{
+ struct mock_phc *phc;
+ int err;
+
+ phc = kzalloc(sizeof(*phc), GFP_KERNEL);
+ if (!phc) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ phc->info = (struct ptp_clock_info) {
+ .owner = THIS_MODULE,
+ .name = "Mock-up PTP clock",
+ .max_adj = MOCK_PHC_MAX_ADJ_PPB,
+ .adjfine = mock_phc_adjfine,
+ .adjtime = mock_phc_adjtime,
+ .gettime64 = mock_phc_gettime64,
+ .settime64 = mock_phc_settime64,
+ .do_aux_work = mock_phc_refresh,
+ };
+
+ phc->cc = (struct cyclecounter) {
+ .read = mock_phc_cc_read,
+ .mask = CYCLECOUNTER_MASK(64),
+ .mult = MOCK_PHC_CC_MULT,
+ .shift = MOCK_PHC_CC_SHIFT,
+ };
+
+ timecounter_init(&phc->tc, &phc->cc, 0);
+
+ phc->clock = ptp_clock_register(&phc->info, dev);
+ if (IS_ERR(phc->clock)) {
+ err = PTR_ERR(phc->clock);
+ goto out_free_phc;
+ }
+
+ ptp_schedule_worker(phc->clock, MOCK_PHC_REFRESH_INTERVAL);
+
+ return phc;
+
+out_free_phc:
+ kfree(phc);
+out:
+ return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(mock_phc_create);
+
+void mock_phc_destroy(struct mock_phc *phc)
+{
+ ptp_clock_unregister(phc->clock);
+ kfree(phc);
+}
+EXPORT_SYMBOL_GPL(mock_phc_destroy);
+
+MODULE_DESCRIPTION("Mock-up PTP Hardware Clock driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/ptp_mock.h b/include/linux/ptp_mock.h
new file mode 100644
index 000000000000..72eb401034d9
--- /dev/null
+++ b/include/linux/ptp_mock.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Mock-up PTP Hardware Clock driver for virtual network devices
+ *
+ * Copyright 2023 NXP
+ */
+
+#ifndef _PTP_MOCK_H_
+#define _PTP_MOCK_H_
+
+struct device;
+struct mock_phc;
+
+#if IS_ENABLED(CONFIG_PTP_1588_CLOCK_MOCK)
+
+struct mock_phc *mock_phc_create(struct device *dev);
+void mock_phc_destroy(struct mock_phc *phc);
+int mock_phc_index(struct mock_phc *phc);
+
+#else
+
+static inline struct mock_phc *mock_phc_create(struct device *dev)
+{
+ return NULL;
+}
+
+static inline void mock_phc_destroy(struct mock_phc *phc)
+{
+}
+
+static inline int mock_phc_index(struct mock_phc *phc)
+{
+ return -1;
+}
+
+#endif
+
+#endif /* _PTP_MOCK_H_ */
--
2.34.1