[PATCH v2 0/2] ptp: split non-NIC PHC drivers into the clock/timekeeping maintenance domain

[PATCH v2 0/2] ptp: split non-NIC PHC drivers into the clock/timekeeping maintenance domain

[Wen Gu]

Hi all,

This series follows the discussion in RFC [1-2] and v1 [3].


# Background

The PTP Hardware Clock (PHC) interface (/dev/ptpX and the standard PTP_*
ioctls) was originally introduced for IEEE 1588 / network oriented clock
drivers. Over time, it has also become a userspace API for many non-NIC
high-precision clock implementations (virtualization/platform/architecture
provided clocks) [4-8], and more are expected to appear [9-10].

During the review of these incoming non IEEE 1588 based PHC drivers, concerns
were raised that such "non-NIC" clocks may not be a good fit for the netdev
maintainership model [11], where PTP/PHC drivers are currently maintained.
This leaves an unclear upstream home and maintainership model for this class
of drivers.


# Proposal

This series proposes moving PHC drivers that expose a high-precision clock to
userspace via the existing PTP interface but are not tied to the traditional
NIC/IEEE 1588 packet timestamping pipeline, out of the netdev maintenance
domain and into the clock/timekeeping maintenance domain.

As discussed in [3], this series makes the separation explicit by reorganizing
the drivers/ptp/ layout into the following groups. This provides clearer
ownership and long-term maintenance boundaries:

  - drivers/ptp/          : PTP core infrastructure and
                            network / IEEE 1588 oriented PTP drivers.

  - drivers/ptp/emulated/ : emulated/virtual PTP drivers. They are typically
                            platform/architecture/virtualization/special
                            hardware provided high-precision time sources.

Patch 1 performs the refactor: move drivers and split Kconfig/Makefiles
accordingly, without intended functional changes.

Patch 2 updates MAINTAINERS to match the new layout and adds a dedicated entry
for drivers/ptp/emulated/, moving review and ownership routing for this class
of drivers away from the netdev maintainership.

No userspace ABI changes are intended; this is a refactor and maintenance
metadata update only.


# Changes since Patch v1:

- List David Woodhouse as the maintainer of emulated PTP drivers.

- Adjust the directory layout: instead of creating both ieee1588/ and
  emulated/ subdirectories, keep the network-oriented drivers in the
  main drivers/ptp/ directory and only split out the emulated drivers.


# Changes since RFC v2:

- Keep ptp_ocp under the IEEE1588/network-oriented PTP drivers as suggested
  by Jakub.

- Following the model used by NTP related code, this series lists tip.git
  (timers/core) as the integration tree for emulated PTP clocks in the
  MAINTAINERS entry. Guidance from clock/timekeeping maintainers
  (Thomas Gleixner, John Stultz, Anna-Maria Behnsen, Frederic Weisbecker,
  Daniel Lezcano, Stephen Boyd) on whether this is the appropriate workflow
  for this class of drivers would be appreciated.

- Continue listing ourselves as maintainers for now as a fallback contact
  point. In the long term it would be preferable for this area to be
  maintained by clock/timekeeping experts, and suggestions are welcome.


Thanks for any input.

Regards.

[1] https://lore.kernel.org/all/0afe19db-9c7f-4228-9fc2-f7b34c4bc227@linux.alibaba.com/
[2] https://lore.kernel.org/all/20260227081934.96865-1-guwen@linux.alibaba.com/
[3] https://lore.kernel.org/all/20260318073330.115808-1-guwen@linux.alibaba.com/
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a0e136d436ded817c0aade72efdefa56a00b4e5e
[5] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7d10001e20e46ad6ad95622164686bc2cbfc9802
[6] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2d7de7a3010d713fb89b7ba99e6fdc14475ad106
[7] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3716a49a81ba19dda7202633a68b28564ba95eb5
[8] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9a17125a18f9ae1e1233a8e2d919059445b9d6fd
[9] https://lore.kernel.org/netdev/20251030121314.56729-1-guwen@linux.alibaba.com/
[10] https://lore.kernel.org/mhi/20250818-tsc_time_sync-v1-0-2747710693ba@oss.qualcomm.com/
[11] https://lore.kernel.org/netdev/20251127083610.6b66a728@kernel.org/

Wen Gu (2):
  ptp: move emulated/virtual clock drivers into a dedicated subdirectory
  MAINTAINERS: update PTP maintainer entries after directory split

 MAINTAINERS                                 | 21 +++++--
 drivers/ptp/Kconfig                         | 68 ++++-----------------
 drivers/ptp/Makefile                        | 11 ++--
 drivers/ptp/emulated/Kconfig                | 61 ++++++++++++++++++
 drivers/ptp/emulated/Makefile               | 11 ++++
 drivers/ptp/{ => emulated}/ptp_kvm_arm.c    |  0
 drivers/ptp/{ => emulated}/ptp_kvm_common.c |  0
 drivers/ptp/{ => emulated}/ptp_kvm_x86.c    |  0
 drivers/ptp/{ => emulated}/ptp_s390.c       |  0
 drivers/ptp/{ => emulated}/ptp_vmclock.c    |  0
 drivers/ptp/{ => emulated}/ptp_vmw.c        |  0
 11 files changed, 103 insertions(+), 69 deletions(-)
 create mode 100644 drivers/ptp/emulated/Kconfig
 create mode 100644 drivers/ptp/emulated/Makefile
 rename drivers/ptp/{ => emulated}/ptp_kvm_arm.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_kvm_common.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_kvm_x86.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_s390.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_vmclock.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_vmw.c (100%)

-- 
2.43.5

[PATCH v2 1/2] ptp: move emulated/virtual clock drivers into a dedicated subdirectory

[Wen Gu]

The PTP subsystem has grown beyond the original IEEE 1588/NIC use case
and today contains both network-oriented PHC drivers and various
emulated/virtual clock implementations.

Prepare for clearer ownership and future maintenance by moving the
emulated/virtual/non-NIC PTP clock drivers into a dedicated subdirectory,
with its own Kconfig and Makefile.

The network/IEEE 1588 oriented drivers remain in drivers/ptp/ alongside
the PTP core infrastructure:

  - drivers/ptp/          : PTP core infrastructure and IEEE 1588 /
                            network-oriented clock drivers.

  - drivers/ptp/emulated/ : emulated/virtual/non-NIC implementations
                            that expose high-precision time sources via
                            the PTP interface but are not tied to the
                            NIC/packet-timestamping pipeline.

No functional changes are intended; this is a refactor only.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 drivers/ptp/Kconfig                         | 68 ++++-----------------
 drivers/ptp/Makefile                        | 11 ++--
 drivers/ptp/emulated/Kconfig                | 61 ++++++++++++++++++
 drivers/ptp/emulated/Makefile               | 11 ++++
 drivers/ptp/{ => emulated}/ptp_kvm_arm.c    |  0
 drivers/ptp/{ => emulated}/ptp_kvm_common.c |  0
 drivers/ptp/{ => emulated}/ptp_kvm_x86.c    |  0
 drivers/ptp/{ => emulated}/ptp_s390.c       |  0
 drivers/ptp/{ => emulated}/ptp_vmclock.c    |  0
 drivers/ptp/{ => emulated}/ptp_vmw.c        |  0
 10 files changed, 87 insertions(+), 64 deletions(-)
 create mode 100644 drivers/ptp/emulated/Kconfig
 create mode 100644 drivers/ptp/emulated/Makefile
 rename drivers/ptp/{ => emulated}/ptp_kvm_arm.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_kvm_common.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_kvm_x86.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_s390.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_vmclock.c (100%)
 rename drivers/ptp/{ => emulated}/ptp_vmw.c (100%)

diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index b93640ca08b7..4cb199332546 100644
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -20,11 +20,16 @@ config PTP_1588_CLOCK
 	  time stamping units, it can be possible to achieve
 	  synchronization to within a few hundred nanoseconds.
 
-	  This driver adds support for PTP clocks as character
-	  devices. If you want to use a PTP clock, then you should
-	  also enable at least one clock driver as well.
+	  This infrastructure adds support for PTP clocks as character
+	  devices. It has since evolved into a general-purpose PTP
+	  clock framework also used by high-precision clocks exposed
+	  by platforms, hypervisors or special hardware, beyond the
+	  traditional NIC/IEEE 1588 use case.
 
-	  To compile this driver as a module, choose M here: the module
+	  If you want to use any PTP clock device, enable this option
+	  and at least one clock driver.
+
+	  To compile the core as a module, choose M here: the module
 	  will be called ptp.
 
 config PTP_1588_CLOCK_OPTIONAL
@@ -119,35 +124,6 @@ config PTP_1588_CLOCK_PCH
 	  To compile this driver as a module, choose M here: the module
 	  will be called ptp_pch.
 
-config PTP_1588_CLOCK_KVM
-	tristate "KVM virtual PTP clock"
-	depends on PTP_1588_CLOCK
-	depends on (KVM_GUEST && X86) || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)
-	default y
-	help
-	  This driver adds support for using kvm infrastructure as a PTP
-	  clock. This clock is only useful if you are using KVM guests.
-
-	  To compile this driver as a module, choose M here: the module
-	  will be called ptp_kvm.
-
-config PTP_1588_CLOCK_VMCLOCK
-	tristate "Virtual machine PTP clock"
-	depends on X86_TSC || ARM_ARCH_TIMER
-	depends on PTP_1588_CLOCK && ARCH_SUPPORTS_INT128
-	default PTP_1588_CLOCK_KVM
-	help
-	  This driver adds support for using a virtual precision clock
-	  advertised by the hypervisor. This clock is only useful in virtual
-	  machines where such a device is present.
-
-	  Unlike the KVM virtual PTP clock, the VMCLOCK device offers support
-	  for reliable timekeeping even across live migration. So this driver
-	  is enabled by default whenever the KVM PTP clock is.
-
-	  To compile this driver as a module, choose M here: the module
-	  will be called ptp_vmclock.
-
 config PTP_1588_CLOCK_IDT82P33
 	tristate "IDT 82P33xxx PTP clock"
 	depends on PTP_1588_CLOCK && I2C
@@ -195,18 +171,6 @@ config PTP_1588_CLOCK_MOCK
 	  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
-	depends on PTP_1588_CLOCK
-	help
-	  This driver adds support for using VMware virtual precision
-	  clock device as a PTP clock. This is only useful in virtual
-	  machines running on VMware virtual infrastructure.
-
-	  To compile this driver as a module, choose M here: the module
-	  will be called ptp_vmw.
-
 config PTP_1588_CLOCK_OCP
 	tristate "OpenCompute TimeCard as PTP clock"
 	depends on PTP_1588_CLOCK
@@ -241,18 +205,6 @@ config PTP_DFL_TOD
 	  To compile this driver as a module, choose M here: the module
 	  will be called ptp_dfl_tod.
 
-config PTP_S390
-	tristate "S390 PTP driver"
-	depends on PTP_1588_CLOCK
-	depends on S390
-	help
-	  This driver adds support for S390 time steering via the PtP
-	  interface. This works by adding a in-kernel clock delta value,
-	  which is always added to time values used in the kernel. The PtP
-	  driver provides the raw clock value without the delta to
-	  userspace. That way userspace programs like chrony could steer
-	  the kernel clock.
-
 config PTP_NETC_V4_TIMER
 	tristate "NXP NETC V4 Timer PTP Driver"
 	depends on PTP_1588_CLOCK
@@ -263,4 +215,6 @@ config PTP_NETC_V4_TIMER
 	  synchronization. It also supports periodic output signal (e.g. PPS)
 	  and external trigger timestamping.
 
+source "drivers/ptp/emulated/Kconfig"
+
 endmenu
diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
index bdc47e284f14..bcea2d3d4efd 100644
--- a/drivers/ptp/Makefile
+++ b/drivers/ptp/Makefile
@@ -1,24 +1,21 @@
 # SPDX-License-Identifier: GPL-2.0
 #
-# Makefile for PTP 1588 clock support.
+# Makefile for PTP clock support.
 #
 
+subdir-ccflags-y += -I$(srctree)/drivers/ptp
+
 ptp-y					:= ptp_clock.o ptp_chardev.o ptp_sysfs.o ptp_vclock.o
-ptp_kvm-$(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
 obj-$(CONFIG_PTP_1588_CLOCK_DTE)	+= ptp_dte.o
 obj-$(CONFIG_PTP_1588_CLOCK_INES)	+= ptp_ines.o
 obj-$(CONFIG_PTP_1588_CLOCK_PCH)	+= ptp_pch.o
-obj-$(CONFIG_PTP_1588_CLOCK_KVM)	+= ptp_kvm.o
-obj-$(CONFIG_PTP_1588_CLOCK_VMCLOCK)	+= ptp_vmclock.o
 obj-$(CONFIG_PTP_1588_CLOCK_QORIQ)	+= ptp_qoriq.o
 obj-$(CONFIG_PTP_1588_CLOCK_IDTCM)	+= ptp_clockmatrix.o
 obj-$(CONFIG_PTP_1588_CLOCK_FC3W)	+= ptp_fc3.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-$(CONFIG_PTP_DFL_TOD)		+= ptp_dfl_tod.o
-obj-$(CONFIG_PTP_S390)			+= ptp_s390.o
 obj-$(CONFIG_PTP_NETC_V4_TIMER)		+= ptp_netc.o
+obj-$(CONFIG_PTP_1588_CLOCK)		+= emulated/
diff --git a/drivers/ptp/emulated/Kconfig b/drivers/ptp/emulated/Kconfig
new file mode 100644
index 000000000000..3e11f78dfbd8
--- /dev/null
+++ b/drivers/ptp/emulated/Kconfig
@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Emulated PTP clock drivers configuration
+#
+
+menu "Emulated PTP clock drivers"
+
+config PTP_1588_CLOCK_KVM
+	tristate "KVM virtual PTP clock"
+	depends on PTP_1588_CLOCK
+	depends on (KVM_GUEST && X86) || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)
+	default y
+	help
+	  This driver adds support for using kvm infrastructure as a PTP
+	  clock. This clock is only useful if you are using KVM guests.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ptp_kvm.
+
+config PTP_1588_CLOCK_VMCLOCK
+	tristate "Virtual machine PTP clock"
+	depends on X86_TSC || ARM_ARCH_TIMER
+	depends on PTP_1588_CLOCK && ARCH_SUPPORTS_INT128
+	default PTP_1588_CLOCK_KVM
+	help
+	  This driver adds support for using a virtual precision clock
+	  advertised by the hypervisor. This clock is only useful in virtual
+	  machines where such a device is present.
+
+	  Unlike the KVM virtual PTP clock, the VMCLOCK device offers support
+	  for reliable timekeeping even across live migration. So this driver
+	  is enabled by default whenever the KVM PTP clock is.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ptp_vmclock.
+
+config PTP_1588_CLOCK_VMW
+	tristate "VMware virtual PTP clock"
+	depends on ACPI && HYPERVISOR_GUEST && X86
+	depends on PTP_1588_CLOCK
+	help
+	  This driver adds support for using VMware virtual precision
+	  clock device as a PTP clock. This is only useful in virtual
+	  machines running on VMware virtual infrastructure.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called ptp_vmw.
+
+config PTP_S390
+	tristate "S390 PTP driver"
+	depends on PTP_1588_CLOCK
+	depends on S390
+	help
+	  This driver adds support for S390 time steering via the PtP
+	  interface. This works by adding a in-kernel clock delta value,
+	  which is always added to time values used in the kernel. The PtP
+	  driver provides the raw clock value without the delta to
+	  userspace. That way userspace programs like chrony could steer
+	  the kernel clock.
+
+endmenu
diff --git a/drivers/ptp/emulated/Makefile b/drivers/ptp/emulated/Makefile
new file mode 100644
index 000000000000..577917df3dc9
--- /dev/null
+++ b/drivers/ptp/emulated/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for emulated PTP clocks.
+#
+
+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-$(CONFIG_PTP_1588_CLOCK_KVM)	+= ptp_kvm.o
+obj-$(CONFIG_PTP_1588_CLOCK_VMCLOCK)	+= ptp_vmclock.o
+obj-$(CONFIG_PTP_1588_CLOCK_VMW)	+= ptp_vmw.o
+obj-$(CONFIG_PTP_S390)			+= ptp_s390.o
diff --git a/drivers/ptp/ptp_kvm_arm.c b/drivers/ptp/emulated/ptp_kvm_arm.c
similarity index 100%
rename from drivers/ptp/ptp_kvm_arm.c
rename to drivers/ptp/emulated/ptp_kvm_arm.c
diff --git a/drivers/ptp/ptp_kvm_common.c b/drivers/ptp/emulated/ptp_kvm_common.c
similarity index 100%
rename from drivers/ptp/ptp_kvm_common.c
rename to drivers/ptp/emulated/ptp_kvm_common.c
diff --git a/drivers/ptp/ptp_kvm_x86.c b/drivers/ptp/emulated/ptp_kvm_x86.c
similarity index 100%
rename from drivers/ptp/ptp_kvm_x86.c
rename to drivers/ptp/emulated/ptp_kvm_x86.c
diff --git a/drivers/ptp/ptp_s390.c b/drivers/ptp/emulated/ptp_s390.c
similarity index 100%
rename from drivers/ptp/ptp_s390.c
rename to drivers/ptp/emulated/ptp_s390.c
diff --git a/drivers/ptp/ptp_vmclock.c b/drivers/ptp/emulated/ptp_vmclock.c
similarity index 100%
rename from drivers/ptp/ptp_vmclock.c
rename to drivers/ptp/emulated/ptp_vmclock.c
diff --git a/drivers/ptp/ptp_vmw.c b/drivers/ptp/emulated/ptp_vmw.c
similarity index 100%
rename from drivers/ptp/ptp_vmw.c
rename to drivers/ptp/emulated/ptp_vmw.c
-- 
2.43.5

[PATCH v2 2/2] MAINTAINERS: update PTP maintainer entries after directory split

[Wen Gu]

Update MAINTAINERS to match the new drivers/ptp/ directory layout after
moving emulated/virtual PTP clock drivers into a new subdirectory.

Adjust file patterns and per-driver entries to point to their new
locations, and add a dedicated MAINTAINERS entry for the emulated PTP
clock drivers.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 MAINTAINERS | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index cb48c9ad9ddc..2b5464e38238 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18335,6 +18335,7 @@ X:	Documentation/devicetree/bindings/net/can/
 X:	Documentation/devicetree/bindings/net/wireless/
 X:	drivers/net/can/
 X:	drivers/net/wireless/
+X:	drivers/ptp/emulated/
 
 NETWORKING DRIVERS (WIRELESS)
 M:	Johannes Berg <johannes@sipsolutions.net>
@@ -21243,8 +21244,18 @@ F:	Documentation/driver-api/ptp.rst
 F:	drivers/net/phy/dp83640*
 F:	drivers/ptp/*
 F:	include/linux/ptp_cl*
+X:	drivers/ptp/emulated/
 K:	(?:\b|_)ptp(?:\b|_)
 
+PTP EMULATED CLOCK SUPPORT
+M:	David Woodhouse <dwmw2@infradead.org>
+M:	Wen Gu <guwen@linux.alibaba.com>
+M:	Xuan Zhuo <xuanzhuo@linux.alibaba.com>
+L:	linux-kernel@vger.kernel.org
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
+F:	drivers/ptp/emulated/
+
 PTP MOCKUP CLOCK SUPPORT
 M:	Vladimir Oltean <vladimir.oltean@nxp.com>
 L:	netdev@vger.kernel.org
@@ -21261,10 +21272,10 @@ F:	net/ethtool/phc_vclocks.c
 
 PTP VMCLOCK SUPPORT
 M:	David Woodhouse <dwmw2@infradead.org>
-L:	netdev@vger.kernel.org
+L:	linux-kernel@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/ptp/amazon,vmclock.yaml
-F:	drivers/ptp/ptp_vmclock.c
+F:	drivers/ptp/emulated/ptp_vmclock.c
 F:	include/uapi/linux/vmclock-abi.h
 
 PTRACE SUPPORT
@@ -23323,7 +23334,7 @@ S390 PTP DRIVER
 M:	Sven Schnelle <svens@linux.ibm.com>
 L:	linux-s390@vger.kernel.org
 S:	Supported
-F:	drivers/ptp/ptp_s390.c
+F:	drivers/ptp/emulated/ptp_s390.c
 
 S390 SCM DRIVER
 M:	Vineeth Vijayan <vneethv@linux.ibm.com>
@@ -28219,9 +28230,9 @@ M:	Nick Shi <nick.shi@broadcom.com>
 R:	Ajay Kaher <ajay.kaher@broadcom.com>
 R:	Alexey Makhalov <alexey.makhalov@broadcom.com>
 R:	Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
-L:	netdev@vger.kernel.org
+L:	linux-kernel@vger.kernel.org
 S:	Supported
-F:	drivers/ptp/ptp_vmw.c
+F:	drivers/ptp/emulated/ptp_vmw.c
 
 VMWARE VMCI DRIVER
 M:	Bryan Tan <bryan-bt.tan@broadcom.com>
-- 
2.43.5