igc: Remove obsolete DMA coalescing code

DMA coalescing is not applicable for i225 parts. This patch comes to tidy
up the driver code.
Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc_defines.h

@@ -662,9 +662,6 @@
  */
 #define IGC_TW_SYSTEM_100_MASK		0x0000FF00
 #define IGC_TW_SYSTEM_100_SHIFT		8
-#define IGC_DMACR_DMAC_EN		0x80000000 /* Enable DMA Coalescing */
-#define IGC_DMACR_DMACTHR_MASK		0x00FF0000
-#define IGC_DMACR_DMACTHR_SHIFT		16
 /* Reg val to set scale to 1024 nsec */
 #define IGC_LTRMINV_SCALE_1024		2
 /* Reg val to set scale to 32768 nsec */

drivers/net/ethernet/intel/igc/igc_i225.c

@@ -593,20 +593,11 @@ s32 igc_set_ltr_i225(struct igc_hw *hw, bool link)
 		size = rd32(IGC_RXPBS) &
 		       IGC_RXPBS_SIZE_I225_MASK;
 
-		/* Calculations vary based on DMAC settings. */
-		if (rd32(IGC_DMACR) & IGC_DMACR_DMAC_EN) {
-			size -= (rd32(IGC_DMACR) &
-				 IGC_DMACR_DMACTHR_MASK) >>
-				 IGC_DMACR_DMACTHR_SHIFT;
-			/* Convert size to bits. */
-			size *= 1024 * 8;
-		} else {
-			/* Convert size to bytes, subtract the MTU, and then
-			 * convert the size to bits.
-			 */
-			size *= 1024;
-			size *= 8;
-		}
+		/* Convert size to bytes, subtract the MTU, and then
+		 * convert the size to bits.
+		 */
+		size *= 1024;
+		size *= 8;
 
 		if (size < 0) {
 			hw_dbg("Invalid effective Rx buffer size %d\n",

drivers/net/ethernet/intel/igc/igc_regs.h

@@ -292,7 +292,6 @@
 
 /* LTR registers */
 #define IGC_LTRC	0x01A0 /* Latency Tolerance Reporting Control */
-#define IGC_DMACR	0x02508 /* DMA Coalescing Control Register */
 #define IGC_LTRMINV	0x5BB0 /* LTR Minimum Value */
 #define IGC_LTRMAXV	0x5BB4 /* LTR Maximum Value */