[Intel-wired-lan] [next-queue PATCH v3 2/2] igc: Add support for ETF offloading

[Vinicius Costa Gomes <vinicius.gomes@intel.com>]

Hi Aaron,

"Brown, Aaron F" <aaron.f.brown@intel.com> writes:

>> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of
>> Vinicius Costa Gomes
>> Sent: Friday, February 14, 2020 3:52 PM
>> To: intel-wired-lan at lists.osuosl.org
>> Subject: [Intel-wired-lan] [next-queue PATCH v3 2/2] igc: Add support for
>> ETF offloading
>> 
>> This adds support for ETF offloading for the i225 controller.
>> 
>> For i225, the LaunchTime feature is almost a subset of the Qbv
>> feature. The main change from the i210 is that the launchtime of each
>> packet is specified as an offset applied to the BASET register. BASET
>> is automatically incremented each cycle.
>> 
>> For i225, the approach chosen is to re-use most of the setup used for
>> taprio offloading. With a few changes:
>> 
>>  - The more or less obvious one is that when ETF is enabled, we should
>>  set add the expected launchtime to the (advanced) transmit
>>  descriptor;
>> 
>>  - The less obvious, is that when taprio offloading is not enabled, we
>>  add a dummy schedule (all queues are open all the time, with a cycle
>>  time of 1 second).
>> 
>> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
>> ---
>>  drivers/net/ethernet/intel/igc/igc_defines.h |  1 +
>>  drivers/net/ethernet/intel/igc/igc_main.c    | 70 +++++++++++++++++++-
>>  drivers/net/ethernet/intel/igc/igc_tsn.c     | 19 +++++-
>>  3 files changed, 86 insertions(+), 4 deletions(-)
>> 
> I'm using the TSN Scheduled TX Tools from https://gist.github.com/jeez/bd3afeff081ba64a695008dd8215866f, and the process (from both the README.etf and README.taprio) seems to work fine with an i210 (igb adapter) but when I try to use the same process with an i225 (igc based adapter) I get a series of Tx Unit Hangs when I start sending traffic.  Packets are still getting sent, but lot of ones just hang.
> ------------------------------------------------------------
> [  936.406229] igc 0000:01:00.0: Detected Tx Unit Hang
>                  Tx Queue             <0>
>                  TDH                  <de>
>                  TDT                  <e4>
>                  next_to_use          <e4>
>                  next_to_clean        <de>
>                buffer_info[next_to_clean]
>                  time_stamp           <100099d84>
>                  next_to_watch        <0000000052519a89>
>                  jiffies              <10009a393>
>                  desc.status          <4a8200>
> [  941.932530] igc 0000:01:00.0: Detected Tx Unit Hang
>                  Tx Queue             <0>
>                  TDH                  <1e>
>                  TDT                  <22>
>                  next_to_use          <22>
>                  next_to_clean        <1e>
>                buffer_info[next_to_clean]
>                  time_stamp           <10009b0e0>
>                  next_to_watch        <00000000ff485dca>
>                  jiffies              <10009bb52>
>                  desc.status          <4a8200>
> [  945.581031] igc 0000:01:00.0: Detected Tx Unit Hang
>                  Tx Queue             <0>
>                  TDH                  <4a>
>                  TDT                  <52>
>                  next_to_use          <52>
>                  next_to_clean        <4a>
>                buffer_info[next_to_clean]
>                  time_stamp           <10009c388>
>                  next_to_watch        <00000000073a6ad3>
>                  jiffies              <10009caff>
>                  desc.status          <4a8200>
>
> ...
> And so on until I stop the talker.  Other (regular) traffic still gets through without any apparent problem.  But only a portion of the etf scheduled ones, the rest left TX Hanging.
>

Thanks for the test.

I only got to reproduce this when the system clock and the NIC PHC are
out of sync, e.g. I only see this when I start udp_tai just after I
start ptp4l/phc2sys.

Just to confirm that we talking about the same problem, if possible,
wait a few minutes before starting udp_tai after starting ptp4l/phc2sys,
and see if the problem persists.

I am trying to think what I can do from the driver side.

Cheers,
-- 
Vinicius