[U-Boot] [PATCH 3/3] pcnet: force ordering of descriptor accesses

[Paul Burton]

The ordering of accesses to the rx & tx descriptors is important, yet
the send & recv functions accessed them via regular structure accesses.
This leaves the compiler with the opportunity to reorder those accesses
or to hoist them outside of loops. Prevent that from happening by using
readl & writel to access the descriptors. As a nice bonus, this removes
the need for the driver to care about endianness.

Signed-off-by: Paul Burton <paul.burton at imgtec.com>
---
 drivers/net/pcnet.c | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/net/pcnet.c b/drivers/net/pcnet.c
index 2802411..237fbba 100644
--- a/drivers/net/pcnet.c
+++ b/drivers/net/pcnet.c
@@ -434,7 +434,7 @@ static int pcnet_send(struct eth_device *dev, void *packet, int pkt_len)
 
 	/* Wait for completion by testing the OWN bit */
 	for (i = 1000; i > 0; i--) {
-		status = le16_to_cpu(entry->status);
+		status = readw(&entry->status);
 		if ((status & 0x8000) == 0)
 			break;
 		udelay(100);
@@ -451,11 +451,10 @@ static int pcnet_send(struct eth_device *dev, void *packet, int pkt_len)
 	 * Setup Tx ring. Caution: the write order is important here,
 	 * set the status with the "ownership" bits last.
 	 */
-	status = 0x8300;
-	entry->length = cpu_to_le16(-pkt_len);
-	entry->misc = 0x00000000;
-	entry->base = PCI_TO_MEM_LE(dev, packet);
-	entry->status = cpu_to_le16(status);
+	writew(-pkt_len, &entry->length);
+	writel(0, &entry->misc);
+	writel(PCI_TO_MEM(dev, packet), &entry->base);
+	writew(0x8300, &entry->status);
 
 	/* Trigger an immediate send poll. */
 	pcnet_write_csr(dev, 0, 0x0008);
@@ -473,34 +472,34 @@ static int pcnet_recv (struct eth_device *dev)
 	struct pcnet_rx_head *entry;
 	unsigned char *buf;
 	int pkt_len = 0;
-	u16 status;
+	u16 status, err_status;
 
 	while (1) {
 		entry = &lp->uc->rx_ring[lp->cur_rx];
 		/*
 		 * If we own the next entry, it's a new packet. Send it up.
 		 */
-		status = le16_to_cpu(entry->status);
+		status = readw(&entry->status);
 		if ((status & 0x8000) != 0)
 			break;
-		status >>= 8;
+		err_status = status >> 8;
 
-		if (status != 0x03) {	/* There was an error. */
+		if (err_status != 0x03) {	/* There was an error. */
 			printf("%s: Rx%d", dev->name, lp->cur_rx);
-			PCNET_DEBUG1(" (status=0x%x)", status);
-			if (status & 0x20)
+			PCNET_DEBUG1(" (status=0x%x)", err_status);
+			if (err_status & 0x20)
 				printf(" Frame");
-			if (status & 0x10)
+			if (err_status & 0x10)
 				printf(" Overflow");
-			if (status & 0x08)
+			if (err_status & 0x08)
 				printf(" CRC");
-			if (status & 0x04)
+			if (err_status & 0x04)
 				printf(" Fifo");
 			printf(" Error\n");
-			entry->status &= le16_to_cpu(0x03ff);
+			status &= 0x03ff;
 
 		} else {
-			pkt_len = (le32_to_cpu(entry->msg_length) & 0xfff) - 4;
+			pkt_len = (readl(&entry->msg_length) & 0xfff) - 4;
 			if (pkt_len < 60) {
 				printf("%s: Rx%d: invalid packet length %d\n",
 				       dev->name, lp->cur_rx, pkt_len);
@@ -513,7 +512,9 @@ static int pcnet_recv (struct eth_device *dev)
 					     lp->cur_rx, pkt_len, buf);
 			}
 		}
-		entry->status |= cpu_to_le16(0x8000);
+
+		status |= 0x8000;
+		writew(status, &entry->status);
 
 		if (++lp->cur_rx >= RX_RING_SIZE)
 			lp->cur_rx = 0;
-- 
1.8.5.3