Re: [PATCH net-next v2 02/12] net: stmmac: Prepare to add Split Header support

In order to add Split Header support, stmmac_rx() needs to take into
account that packet may be split accross multiple descriptors.

Refactor the logic of this function in order to support this scenario.

Signed-off-by: Jose Abreu <redacted>

---
Cc: Giuseppe Cavallaro <redacted>
Cc: Alexandre Torgue <redacted>
Cc: Jose Abreu <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: netdev@vger.kernel.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |   6 +
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 149 +++++++++++++---------
 2 files changed, 95 insertions(+), 60 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 80276587048a..56158e1448ac 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h

@@ -74,6 +74,12 @@ struct stmmac_rx_queue {
 	u32 rx_zeroc_thresh;
 	dma_addr_t dma_rx_phy;
 	u32 rx_tail_addr;
+	unsigned int state_saved;
+	struct {
+		struct sk_buff *skb;
+		unsigned int len;
+		unsigned int error;
+	} state;
 };
 
 struct stmmac_channel {

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b2e5f4ecd551..a093eb4ec275 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -3353,9 +3353,10 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 {
 	struct stmmac_rx_queue *rx_q = &priv->rx_queue[queue];
 	struct stmmac_channel *ch = &priv->channel[queue];
+	unsigned int count = 0, error = 0, len = 0;
+	int status = 0, coe = priv->hw->rx_csum;
 	unsigned int next_entry = rx_q->cur_rx;
-	int coe = priv->hw->rx_csum;
-	unsigned int count = 0;
+	struct sk_buff *skb = NULL;
 
 	if (netif_msg_rx_status(priv)) {
 		void *rx_head;

@@ -3369,9 +3370,27 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 		stmmac_display_ring(priv, rx_head, DMA_RX_SIZE, true);
 	}
 	while (count < limit) {
+		enum pkt_hash_types hash_type;
 		struct stmmac_rx_buffer *buf;
+		unsigned int prev_len = 0;
 		struct dma_desc *np, *p;
-		int entry, status;
+		int entry;
+		u32 hash;
+
+		if (!count && rx_q->state_saved) {
+			skb = rx_q->state.skb;
+			error = rx_q->state.error;
+			len = rx_q->state.len;
+		} else {
+			rx_q->state_saved = false;
+			skb = NULL;
+			error = 0;
+			len = 0;
+		}
+
+read_again:
+		if (count >= limit)
+			break;

 		entry = next_entry;
 		buf = &rx_q->buf_pool[entry];

@@ -3407,28 +3426,24 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 			page_pool_recycle_direct(rx_q->page_pool, buf->page);
 			priv->dev->stats.rx_errors++;
 			buf->page = NULL;
+			error = 1;
+		}
+
+		if (unlikely(error & (status & rx_not_ls)))

+			goto read_again;
+		if (unlikely(error)) {
+			if (skb)
+				dev_kfree_skb(skb);
+			continue;
+		}
+
+		/* Buffer is good. Go on. */
+
+		if (likely(status & rx_not_ls)) {
+			len += priv->dma_buf_sz;
 		} else {
-			enum pkt_hash_types hash_type;
-			struct sk_buff *skb;
-			unsigned int des;
-			int frame_len;
-			u32 hash;
-
-			stmmac_get_desc_addr(priv, p, &des);
-			frame_len = stmmac_get_rx_frame_len(priv, p, coe);
-
-			/*  If frame length is greater than skb buffer size
-			 *  (preallocated during init) then the packet is
-			 *  ignored
-			 */
-			if (frame_len > priv->dma_buf_sz) {
-				if (net_ratelimit())
-					netdev_err(priv->dev,
-						   "len %d larger than size (%d)\n",
-						   frame_len, priv->dma_buf_sz);
-				priv->dev->stats.rx_length_errors++;
-				continue;
-			}
+			prev_len = len;
+			len = stmmac_get_rx_frame_len(priv, p, coe);
 
 			/* ACS is set; GMAC core strips PAD/FCS for IEEE 802.3
 			 * Type frames (LLC/LLC-SNAP)

@@ -3439,57 +3454,71 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 			 */
 			if (unlikely(priv->synopsys_id >= DWMAC_CORE_4_00) ||
 			    unlikely(status != llc_snap))
-				frame_len -= ETH_FCS_LEN;
-
-			if (netif_msg_rx_status(priv)) {
-				netdev_dbg(priv->dev, "\tdesc: %p [entry %d] buff=0x%x\n",
-					   p, entry, des);
-				netdev_dbg(priv->dev, "frame size %d, COE: %d\n",
-					   frame_len, status);
-			}
+				len -= ETH_FCS_LEN;
+		}
 
-			skb = netdev_alloc_skb_ip_align(priv->dev, frame_len);
-			if (unlikely(!skb)) {
+		if (!skb) {
+			skb = netdev_alloc_skb_ip_align(priv->dev, len);