bnxt_en: Separate bnxt_{rx|tx}_ring_info structs from bnxt_napi struct.

Currently, an rx and a tx ring are always paired with a completion ring.
We want to restructure it so that it is possible to have a dedicated
completion ring for tx or rx only.

The bnxt hardware uses a completion ring for rx and tx events.  The driver
has to process the completion ring entries sequentially for the rx and tx
events.  Using a dedicated completion ring for rx only or tx only has these
benefits:

1. A burst of rx packets can cause delay in processing tx events if the
completion ring is shared.  If tx queue is stopped by BQL, this can cause
delay in re-starting the tx queue.

2. A completion ring is sized according to the rx and tx ring size rounded
up to the nearest power of 2.  When the completion ring is shared, it is
sized by adding the rx and tx ring sizes and then rounded to the next power
of 2, often with a lot of wasted space.

3. Using dedicated completion ring, we can adjust the tx and rx coalescing
parameters independently for rx and tx.

The first step is to separate the rx and tx ring structures from the
bnxt_napi struct.

In this patch, an rx ring and a tx ring will point to the same bnxt_napi
struct to share the same completion ring.  No change in ring assignment
and mapping yet.
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt.h

@@ -528,6 +528,7 @@ struct tx_push_bd {
 };
 
 struct bnxt_tx_ring_info {
+	struct bnxt_napi	*bnapi;
 	u16			tx_prod;
 	u16			tx_cons;
 	void __iomem		*tx_doorbell;
@@ -558,6 +559,7 @@ struct bnxt_tpa_info {
 };
 
 struct bnxt_rx_ring_info {
+	struct bnxt_napi	*bnapi;
 	u16			rx_prod;
 	u16			rx_agg_prod;
 	u16			rx_sw_agg_prod;
@@ -604,8 +606,8 @@ struct bnxt_napi {
 
 	int			index;
 	struct bnxt_cp_ring_info	cp_ring;
-	struct bnxt_rx_ring_info	rx_ring;
-	struct bnxt_tx_ring_info	tx_ring;
+	struct bnxt_rx_ring_info	*rx_ring;
+	struct bnxt_tx_ring_info	*tx_ring;
 
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	atomic_t		poll_state;
@@ -884,6 +886,9 @@ struct bnxt {
 
 	struct bnxt_napi	**bnapi;
 
+	struct bnxt_rx_ring_info	*rx_ring;
+	struct bnxt_tx_ring_info	*tx_ring;
+
 	u32			rx_buf_size;
 	u32			rx_buf_use_size;	/* useable size */
 	u32			rx_ring_size;