net: systemport: Fix coalescing settings handling

There were a number of issues with setting the RX coalescing parameters:

- we would not be preserving values that would have been configured
  across close/open calls, instead we would always reset to no timeout
  and 1 interrupt per packet, this would also prevent DIM from setting its
  default usec/pkts values

- when adaptive RX would be turned on, we woud not be fetching the
  default parameters, we would stay with no timeout/1 packet per
  interrupt until the estimator kicks in and changes that

- finally disabling adaptive RX coalescing while providing parameters
  would not be honored, and we would stay with whatever DIM had
  previously determined instead of the user requested parameters

Fixes: b6e0e87542 ("net: systemport: Implement adaptive interrupt coalescing")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Tal Gilboa <talgi@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bcmsysport.h

@@ -701,8 +701,6 @@ struct bcm_sysport_net_dim {
 	u16			event_ctr;
 	unsigned long		packets;
 	unsigned long		bytes;
-	u32			coal_usecs;
-	u32			coal_pkts;
 	struct net_dim		dim;
 };
 
@@ -755,6 +753,8 @@ struct bcm_sysport_priv {
 	unsigned int		rx_c_index;
 
 	struct bcm_sysport_net_dim	dim;
+	u32			rx_max_coalesced_frames;
+	u32			rx_coalesce_usecs;
 
 	/* PHY device */
 	struct device_node	*phy_dn;