1 .. SPDX-License-Identifier: GPL-2.0 2 3 PTP_KVM support for arm/arm64 4 ============================= 5 6 PTP_KVM is used for high precision time sync between host and guests. 7 It relies on transferring the wall clock and counter value from the 8 host to the guest using a KVM-specific hypercall. 9 10 ``ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID`` 11 ---------------------------------------- 12 13 Retrieve current time information for the specific counter. There are no 14 endianness restrictions. 15 16 +---------------------+-------------------------------------------------------+ 17 | Presence: | Optional | 18 +---------------------+-------------------------------------------------------+ 19 | Calling convention: | HVC32 | 20 +---------------------+----------+--------------------------------------------+ 21 | Function ID: | (uint32) | 0x86000001 | 22 +---------------------+----------+----+---------------------------------------+ 23 | Arguments: | (uint32) | R1 | ``KVM_PTP_VIRT_COUNTER (0)`` | 24 | | | +---------------------------------------+ 25 | | | | ``KVM_PTP_PHYS_COUNTER (1)`` | 26 +---------------------+----------+----+---------------------------------------+ 27 | Return Values: | (int32) | R0 | ``NOT_SUPPORTED (-1)`` on error, else | 28 | | | | upper 32 bits of wall clock time | 29 | +----------+----+---------------------------------------+ 30 | | (uint32) | R1 | Lower 32 bits of wall clock time | 31 | +----------+----+---------------------------------------+ 32 | | (uint32) | R2 | Upper 32 bits of counter | 33 | +----------+----+---------------------------------------+ 34 | | (uint32) | R3 | Lower 32 bits of counter | 35 +---------------------+----------+----+---------------------------------------+
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