[PATCH net 1/2] ionic: reject Tx ring sizes below the minimum

["Nikhil P. Rao" <nikhil.rao@amd.com>]

ionic_tx_cq_service() wakes a stopped Tx queue only once
IONIC_TSO_DESCS_NEEDED (44) descriptors are free. The threshold is
sized for a 64 KB TSO skb at a 1500 byte MSS and assumes the ring can
have that many free; a Tx ring of 32 or fewer descriptors cannot, so a
stopped queue is never woken and the netdev watchdog fires.
ionic_set_ringparam() only checks that the size is a power of 2, and
the ethtool core only checks the maximum, so such sizes are accepted.

Reject Tx ring sizes below IONIC_MIN_TXRX_DESC.

Fixes: 061b9bedbef1 ("ionic: Rework Tx start/stop flow")
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
---
 drivers/net/ethernet/pensando/ionic/ionic_ethtool.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c b/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c
index 119ac720c078..3518fbf5882d 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_ethtool.c
@@ -708,6 +708,13 @@ static int ionic_set_ringparam(struct net_device *netdev,
 		return -EINVAL;
 	}
 
+	if (ring->tx_pending < IONIC_MIN_TXRX_DESC) {
+		NL_SET_ERR_MSG_FMT_MOD(extack,
+				       "Tx descriptor count must be at least %d",
+				       IONIC_MIN_TXRX_DESC);
+		return -EINVAL;
+	}
+
 	/* if nothing to do return success */
 	if (ring->tx_pending == lif->ntxq_descs &&
 	    ring->rx_pending == lif->nrxq_descs &&

-- 
2.43.0