nfp: prepare for multi-part descriptors

New datapaths may use multiple descriptor units to describe
a single packet.  Prepare for that by adding a descriptors
per simple frame constant into ring size calculations.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Fei Qin <fei.qin@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfd3/rings.c

@@ -244,6 +244,7 @@ nfp_nfd3_print_tx_descs(struct seq_file *file,
 
 const struct nfp_dp_ops nfp_nfd3_ops = {
 	.version		= NFP_NFD_VER_NFD3,
+	.tx_min_desc_per_pkt	= 1,
 	.poll			= nfp_nfd3_poll,
 	.xsk_poll		= nfp_nfd3_xsk_poll,
 	.ctrl_poll		= nfp_nfd3_ctrl_poll,

drivers/net/ethernet/netronome/nfp/nfp_net.h

@@ -441,8 +441,8 @@ struct nfp_stat_pair {
  * @ctrl_bar:		Pointer to mapped control BAR
  *
  * @ops:		Callbacks and parameters for this vNIC's NFD version
- * @txd_cnt:		Size of the TX ring in number of descriptors
- * @rxd_cnt:		Size of the RX ring in number of descriptors
+ * @txd_cnt:		Size of the TX ring in number of min size packets
+ * @rxd_cnt:		Size of the RX ring in number of min size packets
  * @num_r_vecs:		Number of used ring vectors
  * @num_tx_rings:	Currently configured number of TX rings
  * @num_stack_tx_rings:	Number of TX rings used by the stack (not XDP)

drivers/net/ethernet/netronome/nfp/nfp_net_dp.h

@@ -106,6 +106,7 @@ enum nfp_nfd_version {
 /**
  * struct nfp_dp_ops - Hooks to wrap different implementation of different dp
  * @version:			Indicate dp type
+ * @tx_min_desc_per_pkt:	Minimal TX descs needed for each packet
  * @poll:			Napi poll for normal rx/tx
  * @xsk_poll:			Napi poll when xsk is enabled
  * @ctrl_poll:			Tasklet poll for ctrl rx/tx
@@ -121,6 +122,7 @@ enum nfp_nfd_version {
  */
 struct nfp_dp_ops {
 	enum nfp_nfd_version version;
+	unsigned int tx_min_desc_per_pkt;
 
 	int (*poll)(struct napi_struct *napi, int budget);
 	int (*xsk_poll)(struct napi_struct *napi, int budget);

drivers/net/ethernet/netronome/nfp/nfp_net_ethtool.c

@@ -26,6 +26,7 @@
 #include "nfp_app.h"
 #include "nfp_main.h"
 #include "nfp_net_ctrl.h"
+#include "nfp_net_dp.h"
 #include "nfp_net.h"
 #include "nfp_port.h"
 
@@ -390,7 +391,7 @@ static void nfp_net_get_ringparam(struct net_device *netdev,
 	u32 qc_max = nn->dev_info->max_qc_size;
 
 	ring->rx_max_pending = qc_max;
-	ring->tx_max_pending = qc_max;
+	ring->tx_max_pending = qc_max / nn->dp.ops->tx_min_desc_per_pkt;
 	ring->rx_pending = nn->dp.rxd_cnt;
 	ring->tx_pending = nn->dp.txd_cnt;
 }
@@ -414,8 +415,8 @@ static int nfp_net_set_ringparam(struct net_device *netdev,
 				 struct kernel_ethtool_ringparam *kernel_ring,
 				 struct netlink_ext_ack *extack)
 {
+	u32 tx_dpp, qc_min, qc_max, rxd_cnt, txd_cnt;
 	struct nfp_net *nn = netdev_priv(netdev);
-	u32 qc_min, qc_max, rxd_cnt, txd_cnt;
 
 	/* We don't have separate queues/rings for small/large frames. */
 	if (ring->rx_mini_pending || ring->rx_jumbo_pending)
@@ -423,12 +424,13 @@ static int nfp_net_set_ringparam(struct net_device *netdev,
 
 	qc_min = nn->dev_info->min_qc_size;
 	qc_max = nn->dev_info->max_qc_size;
+	tx_dpp = nn->dp.ops->tx_min_desc_per_pkt;
 	/* Round up to supported values */
 	rxd_cnt = roundup_pow_of_two(ring->rx_pending);
 	txd_cnt = roundup_pow_of_two(ring->tx_pending);
 
 	if (rxd_cnt < qc_min || rxd_cnt > qc_max ||
-	    txd_cnt < qc_min || txd_cnt > qc_max)
+	    txd_cnt < qc_min / tx_dpp || txd_cnt > qc_max / tx_dpp)
 		return -EINVAL;
 
 	if (nn->dp.rxd_cnt == rxd_cnt && nn->dp.txd_cnt == txd_cnt)