net: emaclite: Use indirect reg access in send

The original logic in the driver was exchanging buffers which are used for
sending packet and tx_ping and tx_pong buffers were exchanged all the
time to ensure that IP has enough time to send the packet out.
Based on this "feature" send function was using nextbuffertouse variable
to save which buffer should be used.
Before this algorithm was called driver checked that there is free
buffer available.
This checking remains in the driver but driver tries to use tx_ping
first if available. If not, tx_pong buffer is used instead.
To reach this code the original condition is met that at least one of the
buffer should be available.
Testing doesn't show any performance drop when this patch is applied.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

drivers/net/xilinx_emaclite.c

@@ -24,8 +24,6 @@
 
 /* EmacLite constants */
 #define XEL_BUFFER_OFFSET	0x0800	/* Next buffer's offset */
-#define XEL_TPLR_OFFSET		0x07F4	/* Tx packet length */
-#define XEL_TSR_OFFSET		0x07FC	/* Tx status */
 #define XEL_RSR_OFFSET		0x17FC	/* Rx status */
 #define XEL_RXBUFF_OFFSET	0x1000	/* Receive Buffer */
 
@@ -88,7 +86,6 @@ struct emaclite_regs {
 };
 
 struct xemaclite {
-	u32 nexttxbuffertouse;	/* Next TX buffer to write to */
 	u32 nextrxbuffertouse;	/* Next RX buffer to read from */
 	u32 txpp;		/* TX ping pong buffer */
 	u32 rxpp;		/* RX ping pong buffer */
@@ -126,7 +123,7 @@ static void xemaclite_alignedread(u32 *srcptr, void *destptr, u32 bytecount)
 		*to8ptr++ = *from8ptr++;
 }
 
-static void xemaclite_alignedwrite(void *srcptr, u32 destptr, u32 bytecount)
+static void xemaclite_alignedwrite(void *srcptr, u32 *destptr, u32 bytecount)
 {
 	u32 i;
 	u32 alignbuffer;
@@ -335,7 +332,7 @@ static int emaclite_init(struct eth_device *dev, bd_t *bis)
 	/* Restart PING TX */
 	out_be32(&regs->tx_ping_tsr, 0);
 	/* Copy MAC address */
-	xemaclite_alignedwrite(dev->enetaddr, (u32)&regs->tx_ping,
+	xemaclite_alignedwrite(dev->enetaddr, &regs->tx_ping,
 			       ENET_ADDR_LENGTH);
 	/* Set the length */
 	out_be32(&regs->tx_ping_tplr, ENET_ADDR_LENGTH);
@@ -349,7 +346,7 @@ static int emaclite_init(struct eth_device *dev, bd_t *bis)
 	if (emaclite->txpp) {
 		/* The same operation with PONG TX */
 		out_be32(&regs->tx_pong_tsr, 0);
-		xemaclite_alignedwrite(dev->enetaddr, (u32)&regs->tx_pong,
+		xemaclite_alignedwrite(dev->enetaddr, &regs->tx_pong,
 				       ENET_ADDR_LENGTH);
 		out_be32(&regs->tx_pong_tplr, ENET_ADDR_LENGTH);
 		out_be32(&regs->tx_pong_tsr, XEL_TSR_PROG_MAC_ADDR);
@@ -396,7 +393,6 @@ static int xemaclite_txbufferavailable(struct xemaclite *emaclite)
 static int emaclite_send(struct eth_device *dev, void *ptr, int len)
 {
 	u32 reg;
-	u32 baseaddress;
 	struct xemaclite *emaclite = dev->priv;
 	struct emaclite_regs *regs = emaclite->regs;
 
@@ -420,41 +416,33 @@ static int emaclite_send(struct eth_device *dev, void *ptr, int len)
 		return -1;
 	}
 
-	/* Determine the expected TX buffer address */
-	baseaddress = (dev->iobase + emaclite->nexttxbuffertouse);
-
 	/* Determine if the expected buffer address is empty */
-	reg = in_be32 (baseaddress + XEL_TSR_OFFSET);
+	reg = in_be32(&regs->tx_ping_tsr);
 	if ((reg & XEL_TSR_XMIT_BUSY_MASK) == 0) {
-		if (emaclite->txpp)
-			emaclite->nexttxbuffertouse ^= XEL_BUFFER_OFFSET;
-
-		debug("Send packet from 0x%x\n", baseaddress);
+		debug("Send packet from tx_ping buffer\n");
 		/* Write the frame to the buffer */
-		xemaclite_alignedwrite(ptr, baseaddress, len);
-		out_be32 (baseaddress + XEL_TPLR_OFFSET,(len &
-			(XEL_TPLR_LENGTH_MASK_HI | XEL_TPLR_LENGTH_MASK_LO)));
-		reg = in_be32 (baseaddress + XEL_TSR_OFFSET);
+		xemaclite_alignedwrite(ptr, &regs->tx_ping, len);
+		out_be32(&regs->tx_ping_tplr, len &
+			(XEL_TPLR_LENGTH_MASK_HI | XEL_TPLR_LENGTH_MASK_LO));
+		reg = in_be32(&regs->tx_ping_tsr);
 		reg |= XEL_TSR_XMIT_BUSY_MASK;
-		out_be32 (baseaddress + XEL_TSR_OFFSET, reg);
+		out_be32(&regs->tx_ping_tsr, reg);
 		return 0;
 	}
 
 	if (emaclite->txpp) {
-		/* Switch to second buffer */
-		baseaddress ^= XEL_BUFFER_OFFSET;
 		/* Determine if the expected buffer address is empty */
-		reg = in_be32 (baseaddress + XEL_TSR_OFFSET);
+		reg = in_be32(&regs->tx_pong_tsr);
 		if ((reg & XEL_TSR_XMIT_BUSY_MASK) == 0) {
-			debug("Send packet from 0x%x\n", baseaddress);
+			debug("Send packet from tx_pong buffer\n");
 			/* Write the frame to the buffer */
-			xemaclite_alignedwrite(ptr, baseaddress, len);
-			out_be32 (baseaddress + XEL_TPLR_OFFSET, (len &
-				(XEL_TPLR_LENGTH_MASK_HI |
-					XEL_TPLR_LENGTH_MASK_LO)));
-			reg = in_be32 (baseaddress + XEL_TSR_OFFSET);
+			xemaclite_alignedwrite(ptr, &regs->tx_pong, len);
+			out_be32(&regs->tx_pong_tplr, len &
+				 (XEL_TPLR_LENGTH_MASK_HI |
+				  XEL_TPLR_LENGTH_MASK_LO));
+			reg = in_be32(&regs->tx_pong_tsr);
 			reg |= XEL_TSR_XMIT_BUSY_MASK;
-			out_be32 (baseaddress + XEL_TSR_OFFSET, reg);
+			out_be32(&regs->tx_pong_tsr, reg);
 			return 0;
 		}
 	}