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This patch implements the "ethtool --set-mm" callback to trigger the
frame preemption verification handshake.
Uses the MAC Merge Software Verification (mmsv) mechanism in ethtool
to perform the verification handshake for igc.
The structure fpe.mmsv is set by mmsv in ethtool and should remain
read-only for the driver.
Other mmsv callbacks:
a) configure_tx() -> not used yet at this point
- igc lacks registers to configure FPE in the transmit direction, so
this API is not utilized for now. When igc supports preemptible queue,
driver will use this API to manage its configuration.
b) configure_pmac() -> not used
- this callback dynamically controls pmac_enabled at runtime. For
example, mmsv calls configure_pmac() and disables pmac_enabled when
the link partner goes down, even if the user previously enabled it.
The intention is to save power but it is not feasible in igc
because it causes an endless adapter reset loop:
1) Board A and Board B complete the verification handshake. Tx mode
register for both boards are in TSN mode.
2) Board B link goes down.
On Board A:
3) mmsv calls configure_pmac() with pmac_enabled = false.
4) configure_pmac() in igc updates a new field based on pmac_enabled.
Driver uses this field in igc_tsn_new_flags() to indicate that the
user enabled/disabled FPE.
5) configure_pmac() in igc calls igc_tsn_offload_apply() to check
whether an adapter reset is needed. Calls existing logic in
igc_tsn_will_tx_mode_change() and igc_tsn_new_flags().
6) Since pmac_enabled is now disabled and no other TSN feature is
active, igc_tsn_will_tx_mode_change() evaluates to true because Tx
mode will switch from TSN to Legacy.
7) Driver resets the adapter.
8) Registers are set, and Tx mode switches to Legacy.
9) When link partner is up, steps 3-8 repeat, but this time with
pmac_enabled = true, reactivating TSN.
igc_tsn_will_tx_mode_change() evaluates to true again, since Tx
mode will switch from Legacy to TSN.
10) Driver resets the adapter.
11) Adapter reset completes, registers are set, and Tx mode switches to
TSN.
On Board B:
12) Adapter reset on Board A at step 10 causes it to detect its link
partner as down.
13) Repeats steps 3-8.
14) Once reset adapter on Board A is completed at step 11, it detects
its link partner as up.
15) Repeats steps 9-11.
- this cycle repeats indefinitely. To avoid this issue, igc only uses
mmsv.pmac_enabled to track whether FPE is enabled or disabled.
Co-developed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Co-developed-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
Signed-off-by: Choong Yong Liang <yong.liang.choong@linux.intel.com>
Co-developed-by: Chwee-Lin Choong <chwee.lin.choong@intel.com>
Signed-off-by: Chwee-Lin Choong <chwee.lin.choong@intel.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
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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.