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Voon Weifeng 3600be5f58 net: stmmac: add timestamp correction to rid CDC sync error 
According to Synopsis DesignWare EQoS Databook, the Clock Domain Cross
synchronization error is introduced tue to the clock(GMII Tx/Rx clock)
being different at the capture as compared to the PTP
clock(clk_ptp_ref_i) that is used to generate the time.

The CDC synchronization error is almost equal to 2 times the clock
period of the PTP clock(clk_ptp_ref_i).

On a Intel Tigerlake platform (with Marvell 88E2110 external PHY):

Before applying this patch (with CDC synchronization error):
ptp4l[64.044]: rms    8 max   13 freq +30877 +/-  11 delay   216 +/-   0
ptp4l[65.047]: rms   13 max   20 freq +30869 +/-  17 delay   213 +/-   0
ptp4l[66.050]: rms   12 max   20 freq +30857 +/-  11 delay   213 +/-   0
ptp4l[67.052]: rms   11 max   22 freq +30849 +/-  10 delay   215 +/-   0
ptp4l[68.055]: rms   10 max   16 freq +30853 +/-  13 delay   215 +/-   0
ptp4l[69.057]: rms    7 max   13 freq +30848 +/-   9 delay   216 +/-   0
ptp4l[70.060]: rms    8 max   13 freq +30846 +/-  10 delay   216 +/-   0
ptp4l[71.063]: rms    9 max   15 freq +30836 +/-   8 delay   218 +/-   0

After applying this patch (CDC syncrhonization error is taken care of):
ptp4l[61.516]: rms  773 max  824 freq +31526 +/- 158 delay   200 +/-   0
ptp4l[62.519]: rms  427 max  596 freq +31668 +/-  39 delay   198 +/-   0
ptp4l[63.522]: rms  113 max  206 freq +31482 +/-  57 delay   198 +/-   0
ptp4l[64.525]: rms   40 max   56 freq +31316 +/-  29 delay   200 +/-   0
ptp4l[65.528]: rms   47 max   56 freq +31255 +/-  17 delay   200 +/-   0
ptp4l[66.531]: rms   26 max   36 freq +31246 +/-   9 delay   200 +/-   0
ptp4l[67.534]: rms   12 max   18 freq +31254 +/-  12 delay   202 +/-   0
ptp4l[68.537]: rms    7 max   12 freq +31263 +/-  10 delay   202 +/-   0

Signed-off-by: Voon Weifeng <weifeng.voon@intel.com>
Signed-off-by: Wong Vee Khee <vee.khee.wong@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-03-17 12:04:33 -07:00
arch Merge git://git.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2021-03-09 17:15:56 -08:00
block block/bfq: update comments and default value in docs for fifo_expire 2021-03-02 11:25:38 -07:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto crypto: mips/poly1305 - enable for all MIPS processors 2021-03-08 11:52:17 +01:00
Documentation Documentation: networking: switchdev: fix command for static FDB entries 2021-03-16 15:13:45 -07:00
drivers net: stmmac: add timestamp correction to rid CDC sync error 2021-03-17 12:04:33 -07:00
fs pstore fixes for v5.12-rc2 2021-03-05 17:21:25 -08:00
include ethtool: Add common function for filling out strings 2021-03-17 11:42:30 -07:00
init Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2021-03-09 18:07:05 -08:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2021-03-09 18:07:05 -08:00
lib Merge git://git.kernel.org:/pub/scm/linux/kernel/git/davem/sparc 2021-03-08 22:01:58 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm swap: fix swapfile read/write offset 2021-03-02 17:25:46 -07:00
net tipc: remove some unnecessary warnings 2021-03-17 11:51:05 -07:00
samples samples: pktgen: new append mode 2021-03-14 14:22:38 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2021-03-09 18:07:05 -08:00
security nexthop: Add netlink defines and enumerators for resilient NH groups 2021-03-11 16:12:59 -08:00
sound ALSA: hda/realtek: Apply dual codec quirks for MSI Godlike X570 board 2021-03-03 15:25:03 +01:00
tools selftests: mlxsw: Test egress sampling limitation on Spectrum-1 only 2021-03-16 15:32:23 -07:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: dpaa2-switch: move the driver out of staging 2021-03-10 13:30:36 -08:00
Makefile Linux 5.12-rc2 2021-03-05 17:33:41 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.