Re: [PATCH iwl-net v3 0/6] igc: Fix PTM timeout

[Corinna Vinschen <vinschen@redhat.com>]

Hi Christopher,

is there any new development in terms of this issue?


Thanks,
Corinna


On Nov  6 18:47, Christopher S M Hall wrote:
> 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
> 
> Additional problem description tested by:
> Corinna Vinschen <vinschen@redhat.com>
> 
>   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.
> 
> 
> Changelog:
> 
> v1 -> v2: -Removed patch modifying PTM retry loop count
>       	  -Moved PTM mutex initialization from igc_reset() to igc_ptp_init()
> 	   called once in igc_probe()
> v2 -> v3: -Added mutex_destroy() to clean up PTM lock
> 	  -Added missing checks for PTP enabled flag called from igc_main.c
> 	  -Cleanup PTP module if probe fails
> 	  -Wrap all access to PTM registers with PTM lock/unlock
> 
> Christopher S M Hall (6):
>   igc: Ensure the PTM cycle is reliably triggered
>   igc: Lengthen the hardware retry time to prevent timeouts
>   igc: Move ktime snapshot into PTM retry loop
>   igc: Handle the IGC_PTP_ENABLED flag correctly
>   igc: Cleanup PTP module if probe fails
>   igc: Add lock preventing multiple simultaneous PTM transactions
> 
>  drivers/net/ethernet/intel/igc/igc.h         |   1 +
>  drivers/net/ethernet/intel/igc/igc_defines.h |   3 +-
>  drivers/net/ethernet/intel/igc/igc_main.c    |   1 +
>  drivers/net/ethernet/intel/igc/igc_ptp.c     | 113 ++++++++++++-------
>  4 files changed, 78 insertions(+), 40 deletions(-)
> 
> -- 
> 2.34.1