bnxt_en: reject ETS settings that will starve a TC

ETS proportions are presented to HWRM_QUEUE_COS2BW_CFG as minimum
bandwidth constraints. Thus, zero is a legal value for a given TC.
However, if all the other TCs sum up to 100%, then at least one
hardware queue will starve, resulting in guaranteed TX timeouts.
Reject such nonsensical configurations.

Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c
index 8e90224..8a68df4 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c
@@ -433,6 +433,7 @@ static int bnxt_hwrm_queue_dscp2pri_cfg(struct bnxt *bp, struct dcb_app *app,
 static int bnxt_ets_validate(struct bnxt *bp, struct ieee_ets *ets, u8 *tc)
 {
        int total_ets_bw = 0;
+       bool zero = false;
        u8 max_tc = 0;
        int i;
 
@@ -453,13 +454,20 @@ static int bnxt_ets_validate(struct bnxt *bp, struct ieee_ets *ets, u8 *tc)
                        break;
                case IEEE_8021QAZ_TSA_ETS:
                        total_ets_bw += ets->tc_tx_bw[i];
+                       zero = zero || !ets->tc_tx_bw[i];
                        break;
                default:
                        return -ENOTSUPP;
                }
        }
-       if (total_ets_bw > 100)
+       if (total_ets_bw > 100) {
+               netdev_warn(bp->dev, "rejecting ETS config exceeding available bandwidth\n");
                return -EINVAL;
+       }
+       if (zero && total_ets_bw == 100) {
+               netdev_warn(bp->dev, "rejecting ETS config starving a TC\n");
+               return -EINVAL;
+       }
 
        if (max_tc >= bp->max_tc)
                *tc = bp->max_tc;