When Qav mode is enabled, queue 0 should be kept on Stream Reservation
mode. From the i210 datasheet, section 8.12.19:
"Note: Queue0 QueueMode must be set to 1b when TransmitMode is set to
Qav." ("QueueMode 1b" represents the Stream Reservation mode)
The solution is to give queue 0 the all the credits it might need, so
it has priority over queue 1.
A situation where this can happen is when cbs is "installed" only on
queue 1, leaving queue 0 alone. For example:
$ tc qdisc replace dev enp2s0 handle 100: parent root mqprio num_tc 3 \
map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0
$ tc qdisc replace dev enp2s0 parent 100:2 cbs locredit -1470 \
hicredit 30 sendslope -980000 idleslope 20000 offload 1
Signed-off-by: Vinicius Costa Gomes <vinicius.go...@intel.com>
---
drivers/net/ethernet/intel/igb/igb_main.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
b/drivers/net/ethernet/intel/igb/igb_main.c
index c1c0bc30a16d..cce7ada89255 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -1700,7 +1700,22 @@ static void igb_configure_cbs(struct igb_adapter
*adapter, int queue,
WARN_ON(hw->mac.type != e1000_i210);
WARN_ON(queue < 0 || queue > 1);
- if (enable) {
+ if (enable || queue == 0) {
+ /* i210 does not allow the queue 0 to be in the Strict
+ * Priority mode while the Qav mode is enabled, so,
+ * instead of disabling strict priority mode, we give
+ * queue 0 the maximum of credits possible.
+ *
+ * See section 8.12.19 of the i210 datasheet, "Note:
+ * Queue0 QueueMode must be set to 1b when
+ * TransmitMode is set to Qav."
+ */
+ if (queue == 0 && !enable) {
+ /* max "linkspeed" idleslope in kbps */
+ idleslope = 1000000;
+ hicredit = ETH_FRAME_LEN;
+ }
+
set_tx_desc_fetch_prio(hw, queue, TX_QUEUE_PRIO_HIGH);
set_queue_mode(hw, queue, QUEUE_MODE_STREAM_RESERVATION);
--
2.16.3
