Tony Nguyen says:
====================
igc: Fix PTM timeout
Christopher S M Hall says:
There have been sporadic reports of PTM timeouts using i225/i226 devices
These timeouts have been root caused to:
1) Manipulating the PTM status register while PTM is enabled
and triggered
2) The hardware retrying too quickly when an inappropriate response
is received from the upstream device
The issue can be reproduced with the following:
$ sudo phc2sys -R 1000 -O 0 -i tsn0 -m
Note: 1000 Hz (-R 1000) is unrealistically large, but provides a way to
quickly reproduce the issue.
PHC2SYS exits with:
"ioctl PTP_OFFSET_PRECISE: Connection timed out" when the PTM transaction
fails
The first patch in this series also resolves an issue reported by Corinna
Vinschen relating to kdump:
This patch also fixes a hang in igc_probe() when loading the igc
driver in the kdump kernel on systems supporting PTM.
The igc driver running in the base kernel enables PTM trigger in
igc_probe(). Therefore the driver is always in PTM trigger mode,
except in brief periods when manually triggering a PTM cycle.
When a crash occurs, the NIC is reset while PTM trigger is enabled.
Due to a hardware problem, the NIC is subsequently in a bad busmaster
state and doesn't handle register reads/writes. When running
igc_probe() in the kdump kernel, the first register access to a NIC
register hangs driver probing and ultimately breaks kdump.
With this patch, igc has PTM trigger disabled most of the time,
and the trigger is only enabled for very brief (10 - 100 us) periods
when manually triggering a PTM cycle. Chances that a crash occurs
during a PTM trigger are not zero, but extremly reduced.
* '1GbE' of git://git.kernel.org/pub/scm/linux/kernel/git/tnguy/net-queue:
igc: add lock preventing multiple simultaneous PTM transactions
igc: cleanup PTP module if probe fails
igc: handle the IGC_PTP_ENABLED flag correctly
igc: move ktime snapshot into PTM retry loop
igc: increase wait time before retrying PTM
igc: fix PTM cycle trigger logic
====================
Link: https://patch.msgid.link/20250411162857.2754883-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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