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Jacob Keller ef72678c9d ice: PTP: fix missing timestamps on E825 hardware 
[ Upstream commit 88b68f35eb ]

The E825 hardware currently has each PF handle the PFINT_TSYN_TX cause of
the miscellaneous OICR interrupt vector. The actual interrupt cause
underlying this is shared by all ports on the same quad:

  ┌─────────────────────────────────┐
  │                                 │
  │   ┌────┐ ┌────┐ ┌────┐ ┌────┐   │
  │   │PF 0│ │PF 1│ │PF 2│ │PF 3│   │
  │   └────┘ └────┘ └────┘ └────┘   │
  │                                 │
  └────────────────▲────────────────┘
                   │
                   │
  ┌────────────────┼────────────────┐
  │             PHY QUAD            │
  └───▲────────▲────────▲────────▲──┘
      │        │        │        │
  ┌───┼──┐ ┌───┴──┐ ┌───┼──┐ ┌───┼──┐
  │Port 0│ │Port 1│ │Port 2│ │Port 3│
  └──────┘ └──────┘ └──────┘ └──────┘

If multiple PFs issue Tx timestamp requests near simultaneously, it is
possible that the correct PF will not be interrupted and will miss its
timestamp. Understanding why is somewhat complex.

Consider the following sequence of events:

  CPU 0:
  Send Tx packet on PF 0
  ...
  PF 0 enqueues packet with Tx request          CPU 1, PF1:
  ...                                           Send Tx packet on PF1
  ...                                           PF 1 enqueues packet with Tx request

  HW:
  PHY Port 0 sends packet
  PHY raises Tx timestamp event interrupt
  MAC raises each PF interrupt

  CPU 0, PF0:                                   CPU 1, PF1:
  ice_misc_intr() checks for Tx timestamps      ice_misc_intr() checks for Tx timestamp
  Sees packet ready bit set                     Sees nothing available
  ...                                           Exits
  ...
  ...
  HW:
  PHY port 1 sends packet
  PHY interrupt ignored because not all packet timestamps read yet.
  ...
  Read timestamp, report to stack

Because the interrupt event is shared for all ports on the same quad, the
PHY will not raise a new interrupt for any PF until all timestamps are
read.

In the example above, the second timestamp comes in for port 1 before the
timestamp from port 0 is read. At this point, there is no longer an
interrupt thread running that will read the timestamps, because each PF has
checked and found that there was no work to do. Applications such as ptp4l
will timeout after waiting a few milliseconds. Eventually, the watchdog
service task will re-check for all quads and notice that there are
outstanding timestamps, and issue a software interrupt to recover. However,
by this point it is far too late, and applications have already failed.

All of this occurs because of the underlying hardware behavior. The PHY
cannot raise a new interrupt signal until all outstanding timestamps have
been read.

As a first step to fix this, switch the E825C hardware to the
ICE_PTP_TX_INTERRUPT_ALL mode. In this mode, only the clock owner PF will
respond to the PFINT_TSYN_TX cause. Other PFs disable this cause and will
not wake. In this mode, the clock owner will iterate over all ports and
handle timestamps for each connected port.

This matches the E822 behavior, and is a necessary but insufficient step to
resolve the missing timestamps.

Even with use of the ICE_PTP_TX_INTERRUPT_ALL mode, we still sometimes miss
a timestamp event. The ice_ptp_tx_tstamp_owner() does re-check the ready
bitmap, but does so before re-enabling the OICR interrupt vector. It also
only checks the ready bitmap, but not the software Tx timestamp tracker.

To avoid risk of losing a timestamp, refactor the logic to check both the
software Tx timestamp tracker bitmap *and* the hardware ready bitmap.
Additionally, do this outside of ice_ptp_process_ts() after we have already
re-enabled the OICR interrupt.

Remove the checks from the ice_ptp_tx_tstamp(), ice_ptp_tx_tstamp_owner(),
and the ice_ptp_process_ts() functions. This results in ice_ptp_tx_tstamp()
being nothing more than a wrapper around ice_ptp_process_tx_tstamp() so we
can remove it.

Add the ice_ptp_tx_tstamps_pending() function which returns a boolean
indicating if there are any pending Tx timestamps. First, check the
software timestamp tracker bitmap. In ICE_PTP_TX_INTERRUPT_ALL mode, check
*all* ports software trackers. If a tracker has outstanding timestamp
requests, return true. Additionally, check the PHY ready bitmap to confirm
if the PHY indicates any outstanding timestamps.

In the ice_misc_thread_fn(), call ice_ptp_tx_tstamps_pending() just before
returning from the IRQ thread handler. If it returns true, write to
PFINT_OICR to trigger a PFINT_OICR_TSYN_TX_M software interrupt. This will
force the handler to interrupt again and complete the work even if the PHY
hardware did not interrupt for any reason.

This results in the following new flow for handling Tx timestamps:

1) send Tx packet
2) PHY captures timestamp
3) PHY triggers MAC interrupt
4) clock owner executes ice_misc_intr() with PFINT_OICR_TSYN_TX flag set
5) ice_ptp_ts_irq() returns IRQ_WAKE_THREAD
7) The interrupt thread wakes up and kernel calls ice_misc_intr_thread_fn()
8) ice_ptp_process_ts() is called to handle any outstanding timestamps
9) ice_irq_dynamic_ena() is called to re-enable the OICR hardware interrupt
   cause
10) ice_ptp_tx_tstamps_pending() is called to check if we missed any more
    outstanding timestamps, checking both software and hardware indicators.

With this change, it should no longer be possible for new timestamps to
come in such a way that we lose an interrupt. If a timestamp comes in
before the ice_ptp_tx_tstamps_pending() call, it will be noticed by at
least one of the software bitmap check or the hardware bitmap check. If the
timestamp comes in *after* this check, it should cause a timestamp
interrupt as we have already read all timestamps from the PHY and the OICR
vector has been re-enabled.

Fixes: 7cab44f1c3 ("ice: Introduce ETH56G PHY model for E825C products")
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Przemyslaw Korba <przemyslaw.korba@intel.com>
Tested-by: Vitaly Grinberg <vgrinber@redhat.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-02-11 13:41:55 +01:00
arch riscv: Use 64-bit variable for output in __get_user_asm 2026-02-11 13:41:52 +01:00
block block,bfq: fix aux stat accumulation destination 2026-02-11 13:41:47 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation fou: Don't allow 0 for FOU_ATTR_IPPROTO. 2026-01-30 10:32:12 +01:00
drivers ice: PTP: fix missing timestamps on E825 hardware 2026-02-11 13:41:55 +01:00
fs smb/client: fix memory leak in smb2_open_file() 2026-02-11 13:41:54 +01:00
include net: add skb_header_pointer_careful() helper 2026-02-11 13:41:54 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/rw: free potentially allocated iovec on cache put failure 2026-02-11 13:41:52 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel tracing: Avoid possible signed 64-bit truncation 2026-02-11 13:41:53 +01:00
lib procfs: avoid fetching build ID while holding VMA lock 2026-02-11 13:41:41 +01:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm, shmem: prevent infinite loop on truncate race 2026-02-11 13:41:43 +01:00
net net/sched: cls_u32: use skb_header_pointer_careful() 2026-02-11 13:41:55 +01:00
rust rust: sync: refcount: always inline functions using build_assert with arguments 2026-02-06 16:57:41 +01:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts scripts: generate_rust_analyzer: Add compiler_builtins -> core dep 2026-02-06 16:57:42 +01:00
security keys/trusted_keys: fix handle passed to tpm_buf_append_name during unseal 2026-01-30 10:32:22 +01:00
sound ALSA: hda/realtek: ALC269 fixup for Lenovo Yoga Book 9i 13IRU8 audio 2026-02-11 13:41:53 +01:00
tools KVM: selftests: Add -U_FORTIFY_SOURCE to avoid some unpredictable test failures 2026-02-11 13:41:44 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.9 2026-02-06 16:57:45 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.