netdev - [PATCH net-next V3 08/16] net: fec: set cbd_sc without relying on previous value

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Message-Id: <1459909562-22865-9-git-send-email-troy.kisky@boundarydevices.com>
Date:	Tue,  5 Apr 2016 19:25:54 -0700
From:	Troy Kisky <troy.kisky@...ndarydevices.com>
To:	netdev@...r.kernel.org, davem@...emloft.net, fugang.duan@....com,
	lznuaa@...il.com
Cc:	fabio.estevam@....com, l.stach@...gutronix.de, andrew@...n.ch,
	tremyfr@...il.com, gerg@...inux.org,
	linux-arm-kernel@...ts.infradead.org, johannes@...solutions.net,
	stillcompiling@...il.com, sergei.shtylyov@...entembedded.com,
	arnd@...db.de, Troy Kisky <troy.kisky@...ndarydevices.com>
Subject: [PATCH net-next V3 08/16] net: fec: set cbd_sc without relying on previous value

Relying on the wrap bit of cdb_sc to stay valid once
initialized when the controller also writes to this byte
seems undesirable since we can easily know what the value
should be.

Signed-off-by: Troy Kisky <troy.kisky@...ndarydevices.com>

---
v3: change commit message
---
 drivers/net/ethernet/freescale/fec_main.c | 38 +++++++++----------------------
 1 file changed, 11 insertions(+), 27 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 3cd0cdf..21d2cd0 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -340,9 +340,8 @@ fec_enet_txq_submit_frag_skb(struct fec_enet_priv_tx_q *txq,
 		bdp = fec_enet_get_nextdesc(bdp, &txq->bd);
 		ebdp = (struct bufdesc_ex *)bdp;
 
-		status = fec16_to_cpu(bdp->cbd_sc);
-		status &= ~BD_ENET_TX_STATS;
-		status |= (BD_ENET_TX_TC | BD_ENET_TX_READY);
+		status = BD_ENET_TX_TC | BD_ENET_TX_READY |
+				((bdp == txq->bd.last) ? BD_SC_WRAP : 0);
 		frag_len = skb_shinfo(skb)->frags[frag].size;
 
 		/* Handle the last BD specially */
@@ -436,8 +435,6 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
 	/* Fill in a Tx ring entry */
 	bdp = txq->bd.cur;
 	last_bdp = bdp;
-	status = fec16_to_cpu(bdp->cbd_sc);
-	status &= ~BD_ENET_TX_STATS;
 
 	/* Set buffer length and buffer pointer */
 	bufaddr = skb->data;
@@ -462,6 +459,8 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
 		return NETDEV_TX_OK;
 	}
 
+	status = BD_ENET_TX_TC | BD_ENET_TX_READY |
+			((bdp == txq->bd.last) ? BD_SC_WRAP : 0);
 	if (nr_frags) {
 		last_bdp = fec_enet_txq_submit_frag_skb(txq, skb, ndev);
 		if (IS_ERR(last_bdp)) {
@@ -512,7 +511,6 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq,
 	/* Send it on its way.  Tell FEC it's ready, interrupt when done,
 	 * it's the last BD of the frame, and to put the CRC on the end.
 	 */
-	status |= (BD_ENET_TX_READY | BD_ENET_TX_TC);
 	bdp->cbd_sc = cpu_to_fec16(status);
 
 	/* If this was the last BD in the ring, start at the beginning again. */
@@ -544,11 +542,6 @@ fec_enet_txq_put_data_tso(struct fec_enet_priv_tx_q *txq, struct sk_buff *skb,
 	unsigned int estatus = 0;
 	dma_addr_t addr;
 
-	status = fec16_to_cpu(bdp->cbd_sc);
-	status &= ~BD_ENET_TX_STATS;
-
-	status |= (BD_ENET_TX_TC | BD_ENET_TX_READY);
-
 	if (((unsigned long) data) & fep->tx_align ||
 		fep->quirks & FEC_QUIRK_SWAP_FRAME) {
 		memcpy(txq->tx_bounce[index], data, size);
@@ -578,15 +571,16 @@ fec_enet_txq_put_data_tso(struct fec_enet_priv_tx_q *txq, struct sk_buff *skb,
 		ebdp->cbd_esc = cpu_to_fec32(estatus);
 	}
 
+	status = BD_ENET_TX_TC | BD_ENET_TX_READY |
+			((bdp == txq->bd.last) ? BD_SC_WRAP : 0);
 	/* Handle the last BD specially */
 	if (last_tcp)
-		status |= (BD_ENET_TX_LAST | BD_ENET_TX_TC);
+		status |= BD_ENET_TX_LAST;
 	if (is_last) {
 		status |= BD_ENET_TX_INTR;
 		if (fep->bufdesc_ex)
 			ebdp->cbd_esc |= cpu_to_fec32(BD_ENET_TX_INT);
 	}
-
 	bdp->cbd_sc = cpu_to_fec16(status);
 
 	return 0;
@@ -602,13 +596,8 @@ fec_enet_txq_put_hdr_tso(struct fec_enet_priv_tx_q *txq,
 	struct bufdesc_ex *ebdp = container_of(bdp, struct bufdesc_ex, desc);
 	void *bufaddr;
 	unsigned long dmabuf;
-	unsigned short status;
 	unsigned int estatus = 0;
 
-	status = fec16_to_cpu(bdp->cbd_sc);
-	status &= ~BD_ENET_TX_STATS;
-	status |= (BD_ENET_TX_TC | BD_ENET_TX_READY);
-
 	bufaddr = txq->tso_hdrs + index * TSO_HEADER_SIZE;
 	dmabuf = txq->tso_hdrs_dma + index * TSO_HEADER_SIZE;
 	if (((unsigned long)bufaddr) & fep->tx_align ||
@@ -641,8 +630,8 @@ fec_enet_txq_put_hdr_tso(struct fec_enet_priv_tx_q *txq,
 		ebdp->cbd_esc = cpu_to_fec32(estatus);
 	}
 
-	bdp->cbd_sc = cpu_to_fec16(status);
-
+	bdp->cbd_sc = cpu_to_fec16(BD_ENET_TX_TC | BD_ENET_TX_READY |
+			((bdp == txq->bd.last) ? BD_SC_WRAP : 0));
 	return 0;
 }
 
@@ -1454,12 +1443,6 @@ static int fec_rxq(struct net_device *ndev, struct fec_enet_priv_rx_q *rxq,
 		}
 
 rx_processing_done:
-		/* Clear the status flags for this buffer */
-		status &= ~BD_ENET_RX_STATS;
-
-		/* Mark the buffer empty */
-		status |= BD_ENET_RX_EMPTY;
-
 		if (fep->bufdesc_ex) {
 			struct bufdesc_ex *ebdp = (struct bufdesc_ex *)bdp;
 
@@ -1471,7 +1454,8 @@ rx_processing_done:
 		 * performed before transferring ownership.
 		 */
 		wmb();
-		bdp->cbd_sc = cpu_to_fec16(status);
+		bdp->cbd_sc = cpu_to_fec16(BD_ENET_RX_EMPTY |
+				((bdp == rxq->bd.last) ? BD_SC_WRAP : 0));
 
 		/* Update BD pointer to next entry */
 		bdp = fec_enet_get_nextdesc(bdp, &rxq->bd);
-- 
2.5.0