sfc: Add TX queues for high-priority traffic

Implement the ndo_setup_tc() operation with 2 traffic classes.

Current Solarstorm controllers do not implement TX queue priority, but
they do allow queues to be 'paced' with an enforced delay between
packets.  Paced and unpaced queues are scheduled in round-robin within
two separate hardware bins (paced queues with a large delay may be
placed into a third bin temporarily, but we won't use that).  If there
are queues in both bins, the TX scheduler will alternate between them.

If we make high-priority queues unpaced and best-effort queues paced,
and high-priority queues are mostly empty, a single high-priority queue
can then instantly take 50% of the packet rate regardless of how many
of the best-effort queues have descriptors outstanding.

We do not actually want an enforced delay between packets on best-
effort queues, so we set the pace value to a reserved value that
actually results in a delay of 0.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/net/sfc/regs.h b/drivers/net/sfc/regs.h
index 96430ed..8227de6 100644
--- a/drivers/net/sfc/regs.h
+++ b/drivers/net/sfc/regs.h
@@ -2907,6 +2907,12 @@
 #define FRF_CZ_TMFT_SRC_MAC_HI_LBN 44
 #define FRF_CZ_TMFT_SRC_MAC_HI_WIDTH 16
 
+/* TX_PACE_TBL */
+/* Values >20 are documented as reserved, but will result in a queue going
+ * into the fast bin with a pace value of zero. */
+#define FFE_BZ_TX_PACE_OFF 0
+#define FFE_BZ_TX_PACE_RESERVED 21
+
 /* DRIVER_EV */
 /* Sub-fields of an RX flush completion event */
 #define FSF_AZ_DRIVER_EV_RX_FLUSH_FAIL_LBN 12