e1000e: apply burst mode settings only on default

Devices that support FLAG2_DMA_BURST have different default values
for RDTR and RADV. Apply burst mode default settings only when no
explicit value was passed at module load.

The RDTR default is zero. If the module is loaded for low latency
operation with RxIntDelay=0, do not override this value with a burst
default of 32.

Move the decision to apply burst values earlier, where explicitly
initialized module variables can be distinguished from defaults.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/e1000.h

@@ -94,10 +94,6 @@ struct e1000_info;
  */
 #define E1000_CHECK_RESET_COUNT		25
 
-#define DEFAULT_RDTR			0
-#define DEFAULT_RADV			8
-#define BURST_RDTR			0x20
-#define BURST_RADV			0x20
 #define PCICFG_DESC_RING_STATUS		0xe4
 #define FLUSH_DESC_REQUIRED		0x100
 

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -3242,14 +3242,6 @@ static void e1000_configure_rx(struct e1000_adapter *adapter)
 		 */
 		ew32(RXDCTL(0), E1000_RXDCTL_DMA_BURST_ENABLE);
 		ew32(RXDCTL(1), E1000_RXDCTL_DMA_BURST_ENABLE);
-
-		/* override the delay timers for enabling bursting, only if
-		 * the value was not set by the user via module options
-		 */
-		if (adapter->rx_int_delay == DEFAULT_RDTR)
-			adapter->rx_int_delay = BURST_RDTR;
-		if (adapter->rx_abs_int_delay == DEFAULT_RADV)
-			adapter->rx_abs_int_delay = BURST_RADV;
 	}
 
 	/* set the Receive Delay Timer Register */

drivers/net/ethernet/intel/e1000e/param.c

@@ -73,17 +73,25 @@ E1000_PARAM(TxAbsIntDelay, "Transmit Absolute Interrupt Delay");
 /* Receive Interrupt Delay in units of 1.024 microseconds
  * hardware will likely hang if you set this to anything but zero.
  *
+ * Burst variant is used as default if device has FLAG2_DMA_BURST.
+ *
  * Valid Range: 0-65535
  */
 E1000_PARAM(RxIntDelay, "Receive Interrupt Delay");
+#define DEFAULT_RDTR	0
+#define BURST_RDTR	0x20
 #define MAX_RXDELAY 0xFFFF
 #define MIN_RXDELAY 0
 
 /* Receive Absolute Interrupt Delay in units of 1.024 microseconds
+ *
+ * Burst variant is used as default if device has FLAG2_DMA_BURST.
  *
  * Valid Range: 0-65535
  */
 E1000_PARAM(RxAbsIntDelay, "Receive Absolute Interrupt Delay");
+#define DEFAULT_RADV	8
+#define BURST_RADV	0x20
 #define MAX_RXABSDELAY 0xFFFF
 #define MIN_RXABSDELAY 0
 
@@ -297,6 +305,9 @@ void e1000e_check_options(struct e1000_adapter *adapter)
 					 .max = MAX_RXDELAY } }
 		};
 
+		if (adapter->flags2 & FLAG2_DMA_BURST)
+			opt.def = BURST_RDTR;
+
 		if (num_RxIntDelay > bd) {
 			adapter->rx_int_delay = RxIntDelay[bd];
 			e1000_validate_option(&adapter->rx_int_delay, &opt,
@@ -307,7 +318,7 @@ void e1000e_check_options(struct e1000_adapter *adapter)
 	}
 	/* Receive Absolute Interrupt Delay */
 	{
-		static const struct e1000_option opt = {
+		static struct e1000_option opt = {
 			.type = range_option,
 			.name = "Receive Absolute Interrupt Delay",
 			.err  = "using default of "
@@ -317,6 +328,9 @@ void e1000e_check_options(struct e1000_adapter *adapter)
 					 .max = MAX_RXABSDELAY } }
 		};
 
+		if (adapter->flags2 & FLAG2_DMA_BURST)
+			opt.def = BURST_RADV;
+
 		if (num_RxAbsIntDelay > bd) {
 			adapter->rx_abs_int_delay = RxAbsIntDelay[bd];
 			e1000_validate_option(&adapter->rx_abs_int_delay, &opt,