[Intel-wired-lan] [PATCH iwl-net v1 1/5] igc: Ensure the PTM cycle is reliably triggered

[Corinna Vinschen]

Hi Christopher,

On Aug  7 20:27, Hall, Christopher S wrote:
> Hi Corrina,

s/rrin/rinn/ ;)

> > > PHC2SYS exits with:
> > >
> > > "ioctl PTP_OFFSET_PRECISE: Connection timed out" when the PTM
> > transaction
> > >   fails
> > 
> > It would be great to add the problems encountered with kdump to the
> > commit message as well, as discussed with Vinicius, wouldn't it?
> > 
> > If you need a description, I can provide one.
> 
> Does this patch fix the issue you observed?

Yes, it does.  

> If it does, I am happy to
> include your description of the problem it solves.

Is the following ok?

  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 0, but extremly reduced.

> A tested-by tag would be appreciated as well.

Reviewed-by: Corinna Vinschen <vinschen at redhat.com>
Tested-by: Corinna Vinschen <vinschen at redhat.com> (kdump hang only)


Thanks,
Corinna