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Florian Kauer 8b86f10ab6 igc: No strict mode in pure launchtime/CBS offload 
The flags IGC_TXQCTL_STRICT_CYCLE and IGC_TXQCTL_STRICT_END
prevent the packet transmission over slot and cycle boundaries.
This is important for taprio offload where the slots and
cycles correspond to the slots and cycles configured for the
network.

However, the Qbv offload feature of the i225 is also used for
enabling TX launchtime / ETF offload. In that case, however,
the cycle has no meaning for the network and is only used
internally to adapt the base time register after a second has
passed.

Enabling strict mode in this case would unnecessarily prevent
the transmission of certain packets (i.e. at the boundary of a
second) and thus interferes with the ETF qdisc that promises
transmission at a certain point in time.

Similar to ETF, this also applies to CBS offload that also should
not be influenced by strict mode unless taprio offload would be
enabled at the same time.

This fully reverts
commit d8f45be01d ("igc: Use strict cycles for Qbv scheduling")
but its commit message only describes what was already implemented
before that commit. The difference to a plain revert of that commit
is that it now copes with the base_time = 0 case that was fixed with
commit e17090eb24 ("igc: allow BaseTime 0 enrollment for Qbv")

In particular, enabling strict mode leads to TX hang situations
under high traffic if taprio is applied WITHOUT taprio offload
but WITH ETF offload, e.g. as in

    sudo tc qdisc replace dev enp1s0 parent root handle 100 taprio \
	    num_tc 1 \
	    map 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
	    queues 1@0 \
	    base-time 0 \
	    sched-entry S 01 300000 \
	    flags 0x1 \
	    txtime-delay 500000 \
	    clockid CLOCK_TAI
    sudo tc qdisc replace dev enp1s0 parent 100:1 etf \
	    clockid CLOCK_TAI \
	    delta 500000 \
	    offload \
	    skip_sock_check

and traffic generator

    sudo trafgen -i traffic.cfg -o enp1s0 --cpp -n0 -q -t1400ns

with traffic.cfg

    #define ETH_P_IP        0x0800

    {
      /* Ethernet Header */
      0x30, 0x1f, 0x9a, 0xd0, 0xf0, 0x0e,  # MAC Dest - adapt as needed
      0x24, 0x5e, 0xbe, 0x57, 0x2e, 0x36,  # MAC Src  - adapt as needed
      const16(ETH_P_IP),

      /* IPv4 Header */
      0b01000101, 0,   # IPv4 version, IHL, TOS
      const16(1028),   # IPv4 total length (UDP length + 20 bytes (IP header))
      const16(2),      # IPv4 ident
      0b01000000, 0,   # IPv4 flags, fragmentation off
      64,              # IPv4 TTL
      17,              # Protocol UDP
      csumip(14, 33),  # IPv4 checksum

      /* UDP Header */
      10,  0, 48, 1,   # IP Src - adapt as needed
      10,  0, 48, 10,  # IP Dest - adapt as needed
      const16(5555),   # UDP Src Port
      const16(6666),   # UDP Dest Port
      const16(1008),   # UDP length (UDP header 8 bytes + payload length)
      csumudp(14, 34), # UDP checksum

      /* Payload */
      fill('W', 1000),
    }

and the observed message with that is for example

 igc 0000:01:00.0 enp1s0: Detected Tx Unit Hang
   Tx Queue             <0>
   TDH                  <d0>
   TDT                  <f0>
   next_to_use          <f0>
   next_to_clean        <d0>
 buffer_info[next_to_clean]
   time_stamp           <ffff661f>
   next_to_watch        <00000000245a4efb>
   jiffies              <ffff6e48>
   desc.status          <1048000>

Fixes: d8f45be01d ("igc: Use strict cycles for Qbv scheduling")
Signed-off-by: Florian Kauer <florian.kauer@linutronix.de>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
2023-07-10 08:58:16 -07:00
arch parisc architecture fixes and updates for kernel v6.5-rc1 (pt 2): 2023-07-05 10:28:38 -07:00
block block-6.5-2023-07-03 2023-07-03 18:48:38 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto This update includes the following changes: 2023-06-30 21:27:13 -07:00
Documentation Including fixes from bluetooth, bpf and wireguard. 2023-07-05 15:44:45 -07:00
drivers igc: No strict mode in pure launchtime/CBS offload 2023-07-10 08:58:16 -07:00
fs f2fs update for 6.5-rc1 2023-07-05 14:14:37 -07:00
include s390/ism: Fix and simplify add()/remove() callback handling 2023-07-08 10:07:14 +01:00
init Kbuild updates for v6.5 2023-07-01 09:24:31 -07:00
io_uring io_uring-6.5-2023-07-03 2023-07-03 18:43:10 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel Including fixes from bluetooth, bpf and wireguard. 2023-07-05 15:44:45 -07:00
lib Char/Misc and other driver subsystem updates for 6.5-rc1 2023-07-03 12:46:47 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm gup: make the stack expansion warning a bit more targeted 2023-07-05 09:33:31 -07:00
net net: sched: Replace strlcpy with strscpy 2023-07-10 08:23:53 +01:00
rust rust: error: impl Debug for Error with errname() integration 2023-06-13 01:24:42 +02:00
samples Including fixes from bluetooth, bpf and wireguard. 2023-07-05 15:44:45 -07:00
scripts parisc architecture fixes and updates for kernel v6.5-rc1 (pt 2): 2023-07-05 10:28:38 -07:00
security Scope-based Resource Management infrastructure 2023-07-04 13:50:38 -07:00
sound soundwire updates for 6.5 2023-07-05 10:54:43 -07:00
tools Including fixes from bluetooth, bpf and wireguard. 2023-07-05 15:44:45 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM64: 2023-07-03 15:32:22 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap - New Drivers 2023-07-03 10:55:04 -07:00
.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 - Address -Wmissing-prototype warnings 2023-06-26 16:43:54 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS pwm: Changes for v6.5-rc1 2023-07-05 12:55:06 -07:00
Makefile Scope-based Resource Management infrastructure 2023-07-04 13:50:38 -07:00
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.