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Currently, there is no mechanism to keep time sync between guest and host in arm/arm64 virtualization environment. Time in guest will drift compared with host after boot up as they may both use third party time sources to correct their time respectively. The time deviation will be in order of milliseconds. But in some scenarios,like in cloud environment, we ask for higher time precision. kvm ptp clock, which chooses the host clock source as a reference clock to sync time between guest and host, has been adopted by x86 which takes the time sync order from milliseconds to nanoseconds. This patch enables kvm ptp clock for arm/arm64 and improves clock sync precision significantly. Test result comparisons between with kvm ptp clock and without it in arm/arm64 are as follows. This test derived from the result of command 'chronyc sources'. we should take more care of the last sample column which shows the offset between the local clock and the source at the last measurement. no kvm ptp in guest: MS Name/IP address Stratum Poll Reach LastRx Last sample ======================================================================== ^* dns1.synet.edu.cn 2 6 377 13 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 21 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 29 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 37 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 45 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 53 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 61 +1040us[+1581us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 4 -130us[ +796us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 12 -130us[ +796us] +/- 21ms ^* dns1.synet.edu.cn 2 6 377 20 -130us[ +796us] +/- 21ms in host: MS Name/IP address Stratum Poll Reach LastRx Last sample ======================================================================== ^* 120.25.115.20 2 7 377 72 -470us[ -603us] +/- 18ms ^* 120.25.115.20 2 7 377 92 -470us[ -603us] +/- 18ms ^* 120.25.115.20 2 7 377 112 -470us[ -603us] +/- 18ms ^* 120.25.115.20 2 7 377 2 +872ns[-6808ns] +/- 17ms ^* 120.25.115.20 2 7 377 22 +872ns[-6808ns] +/- 17ms ^* 120.25.115.20 2 7 377 43 +872ns[-6808ns] +/- 17ms ^* 120.25.115.20 2 7 377 63 +872ns[-6808ns] +/- 17ms ^* 120.25.115.20 2 7 377 83 +872ns[-6808ns] +/- 17ms ^* 120.25.115.20 2 7 377 103 +872ns[-6808ns] +/- 17ms ^* 120.25.115.20 2 7 377 123 +872ns[-6808ns] +/- 17ms The dns1.synet.edu.cn is the network reference clock for guest and 120.25.115.20 is the network reference clock for host. we can't get the clock error between guest and host directly, but a roughly estimated value will be in order of hundreds of us to ms. with kvm ptp in guest: chrony has been disabled in host to remove the disturb by network clock. MS Name/IP address Stratum Poll Reach LastRx Last sample ======================================================================== * PHC0 0 3 377 8 -7ns[ +1ns] +/- 3ns * PHC0 0 3 377 8 +1ns[ +16ns] +/- 3ns * PHC0 0 3 377 6 -4ns[ -0ns] +/- 6ns * PHC0 0 3 377 6 -8ns[ -12ns] +/- 5ns * PHC0 0 3 377 5 +2ns[ +4ns] +/- 4ns * PHC0 0 3 377 13 +2ns[ +4ns] +/- 4ns * PHC0 0 3 377 12 -4ns[ -6ns] +/- 4ns * PHC0 0 3 377 11 -8ns[ -11ns] +/- 6ns * PHC0 0 3 377 10 -14ns[ -20ns] +/- 4ns * PHC0 0 3 377 8 +4ns[ +5ns] +/- 4ns The PHC0 is the ptp clock which choose the host clock as its source clock. So we can see that the clock difference between host and guest is in order of ns. Cc: Mark Rutland <mark.rutland@arm.com> Acked-by: Richard Cochran <richardcochran@gmail.com> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20201209060932.212364-8-jianyong.wu@arm.com
171 lines
5.5 KiB
Plaintext
171 lines
5.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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#
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# PTP clock support configuration
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#
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menu "PTP clock support"
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config PTP_1588_CLOCK
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tristate "PTP clock support"
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depends on NET && POSIX_TIMERS
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select PPS
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select NET_PTP_CLASSIFY
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help
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The IEEE 1588 standard defines a method to precisely
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synchronize distributed clocks over Ethernet networks. The
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standard defines a Precision Time Protocol (PTP), which can
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be used to achieve synchronization within a few dozen
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microseconds. In addition, with the help of special hardware
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time stamping units, it can be possible to achieve
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synchronization to within a few hundred nanoseconds.
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This driver adds support for PTP clocks as character
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devices. If you want to use a PTP clock, then you should
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also enable at least one clock driver as well.
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To compile this driver as a module, choose M here: the module
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will be called ptp.
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config PTP_1588_CLOCK_DTE
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tristate "Broadcom DTE as PTP clock"
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depends on PTP_1588_CLOCK
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depends on NET && HAS_IOMEM
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depends on ARCH_BCM_MOBILE || (ARCH_BCM_IPROC && !(ARCH_BCM_NSP || ARCH_BCM_5301X)) || COMPILE_TEST
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default y
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help
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This driver adds support for using the Digital timing engine
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(DTE) in the Broadcom SoC's as a PTP clock.
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The clock can be used in both wired and wireless networks
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for PTP purposes.
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To compile this driver as a module, choose M here: the module
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will be called ptp_dte.
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config PTP_1588_CLOCK_QORIQ
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tristate "Freescale QorIQ 1588 timer as PTP clock"
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depends on GIANFAR || FSL_DPAA_ETH || FSL_DPAA2_ETH || FSL_ENETC || FSL_ENETC_VF || COMPILE_TEST
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depends on PTP_1588_CLOCK
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default y
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help
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This driver adds support for using the Freescale QorIQ 1588
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timer as a PTP clock. This clock is only useful if your PTP
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programs are getting hardware time stamps on the PTP Ethernet
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packets using the SO_TIMESTAMPING API.
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To compile this driver as a module, choose M here: the module
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will be called ptp-qoriq.
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comment "Enable PHYLIB and NETWORK_PHY_TIMESTAMPING to see the additional clocks."
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depends on PHYLIB=n || NETWORK_PHY_TIMESTAMPING=n
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config DP83640_PHY
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tristate "Driver for the National Semiconductor DP83640 PHYTER"
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depends on NETWORK_PHY_TIMESTAMPING
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depends on PHYLIB
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depends on PTP_1588_CLOCK
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select CRC32
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help
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Supports the DP83640 PHYTER with IEEE 1588 features.
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This driver adds support for using the DP83640 as a PTP
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clock. This clock is only useful if your PTP programs are
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getting hardware time stamps on the PTP Ethernet packets
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using the SO_TIMESTAMPING API.
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In order for this to work, your MAC driver must also
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implement the skb_tx_timestamp() function.
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config PTP_1588_CLOCK_INES
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tristate "ZHAW InES PTP time stamping IP core"
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depends on NETWORK_PHY_TIMESTAMPING
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depends on HAS_IOMEM
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depends on PHYLIB
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depends on PTP_1588_CLOCK
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help
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This driver adds support for using the ZHAW InES 1588 IP
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core. This clock is only useful if the MII bus of your MAC
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is wired up to the core.
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config PTP_1588_CLOCK_PCH
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tristate "Intel PCH EG20T as PTP clock"
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depends on X86_32 || COMPILE_TEST
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depends on HAS_IOMEM && NET
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imply PTP_1588_CLOCK
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help
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This driver adds support for using the PCH EG20T as a PTP
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clock. The hardware supports time stamping of PTP packets
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when using the end-to-end delay (E2E) mechanism. The peer
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delay mechanism (P2P) is not supported.
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This clock is only useful if your PTP programs are getting
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hardware time stamps on the PTP Ethernet packets using the
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SO_TIMESTAMPING API.
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To compile this driver as a module, choose M here: the module
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will be called ptp_pch.
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config PTP_1588_CLOCK_KVM
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tristate "KVM virtual PTP clock"
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depends on PTP_1588_CLOCK
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depends on (KVM_GUEST && X86) || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)
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default y
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help
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This driver adds support for using kvm infrastructure as a PTP
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clock. This clock is only useful if you are using KVM guests.
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To compile this driver as a module, choose M here: the module
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will be called ptp_kvm.
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config PTP_1588_CLOCK_IDT82P33
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tristate "IDT 82P33xxx PTP clock"
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depends on PTP_1588_CLOCK && I2C
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default n
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help
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This driver adds support for using the IDT 82P33xxx as a PTP
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clock. This clock is only useful if your time stamping MAC
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is connected to the IDT chip.
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To compile this driver as a module, choose M here: the module
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will be called ptp_idt82p33.
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config PTP_1588_CLOCK_IDTCM
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tristate "IDT CLOCKMATRIX as PTP clock"
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depends on PTP_1588_CLOCK && I2C
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default n
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help
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This driver adds support for using IDT CLOCKMATRIX(TM) as a PTP
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clock. This clock is only useful if your time stamping MAC
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is connected to the IDT chip.
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To compile this driver as a module, choose M here: the module
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will be called ptp_clockmatrix.
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config PTP_1588_CLOCK_VMW
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tristate "VMware virtual PTP clock"
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depends on ACPI && HYPERVISOR_GUEST && X86
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depends on PTP_1588_CLOCK
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help
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This driver adds support for using VMware virtual precision
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clock device as a PTP clock. This is only useful in virtual
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machines running on VMware virtual infrastructure.
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To compile this driver as a module, choose M here: the module
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will be called ptp_vmw.
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config PTP_1588_CLOCK_OCP
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tristate "OpenCompute TimeCard as PTP clock"
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depends on PTP_1588_CLOCK
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depends on HAS_IOMEM && PCI
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default n
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help
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This driver adds support for an OpenCompute time card.
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The OpenCompute time card is an atomic clock along with
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a GPS receiver that provides a Grandmaster clock source
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for a PTP enabled network.
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More information is available at http://www.timingcard.com/
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endmenu
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