nfp: use TX ring pointer write back

Newer versions of the PCIe microcode support writing back the
position of the TX pointer back into host memory.  This speeds
up TX completions, because we avoid a read from device memory
(replacing PCIe read with DMA coherent read).

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>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net.h b/drivers/net/ethernet/netronome/nfp/nfp_net.h
index 4e288b8f3510..3c386972f69a 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net.h
@@ -126,6 +126,7 @@ struct nfp_nfd3_tx_buf;
  * @r_vec:      Back pointer to ring vector structure
  * @idx:        Ring index from Linux's perspective
  * @qcp_q:      Pointer to base of the QCP TX queue
+ * @txrwb:	TX pointer write back area
  * @cnt:        Size of the queue in number of descriptors
  * @wr_p:       TX ring write pointer (free running)
  * @rd_p:       TX ring read pointer (free running)
@@ -145,6 +146,7 @@ struct nfp_net_tx_ring {
 
 	u32 idx;
 	u8 __iomem *qcp_q;
+	u64 *txrwb;
 
 	u32 cnt;
 	u32 wr_p;
@@ -444,6 +446,8 @@ struct nfp_stat_pair {
  * @ctrl_bar:		Pointer to mapped control BAR
  *
  * @ops:		Callbacks and parameters for this vNIC's NFD version
+ * @txrwb:		TX pointer write back area (indexed by queue id)
+ * @txrwb_dma:		TX pointer write back area DMA address
  * @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
@@ -480,6 +484,9 @@ struct nfp_net_dp {
 
 	const struct nfp_dp_ops *ops;
 
+	u64 *txrwb;
+	dma_addr_t txrwb_dma;
+
 	unsigned int txd_cnt;
 	unsigned int rxd_cnt;